Rhodos, Vol. 2, No. 13
- Date: 1990-09-13
- Subjects: Rhodes University -- Rhodos , Grahamstown -- Newspapers
- Language: English
- Type: Text
- Identifier: vital:14813 , http://hdl.handle.net/10962/d1019052
- Description: The Rhodos newsletter carries news and information about events, awards, projects and developments both on and off campus. Ten editions of Rhodos are printed throughout the academic year for distribution among staff members of the University
- Full Text:
- Date Issued: 1990-09-13
- Date: 1990-09-13
- Subjects: Rhodes University -- Rhodos , Grahamstown -- Newspapers
- Language: English
- Type: Text
- Identifier: vital:14813 , http://hdl.handle.net/10962/d1019052
- Description: The Rhodos newsletter carries news and information about events, awards, projects and developments both on and off campus. Ten editions of Rhodos are printed throughout the academic year for distribution among staff members of the University
- Full Text:
- Date Issued: 1990-09-13
A survey of employee preferences in the design of a performance management system
- Authors: Keshave, Hiten
- Date: 2016
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:863 , http://hdl.handle.net/10962/d1021180
- Description: This thesis begins with an introduction to performance management and the intended aim and objective of the research. Thereafter literature findings relative to performance management and performance management systems are discussed. In the review of literature, three processes that could be implemented in a performance management system were highlighted, namely; (1) the planning process, (2) the monitoring and development process, and (3) an annual summative and feedback process. Performance management functions deemed important to employees during each process of the performance management system were identified and discussed. Subsequent to the literature review, the research methodology was described and involved the implementation of quantitative research within a post-positivist paradigm in the form of a close-ended survey questionnaire. Analysis of the data involved a gap analysis and needs analysis. The gap analysis study was based on the opinion of management respondents in comparison to the opinion of non-management respondents. Results of the gap analysis were determined based on the calculation of an importance score for each sub-group. The needs analysis study was based on the overall opinion of all respondents, and results were determined based on the calculation of an overall importance score. In light of the literature review that was conducted to inform the questionnaire design, the survey results supported the literature review of each discussed performance management function with no evident contradictions. The results of the gap analysis and needs analysis were satisfactorily met for each performance management function. On the basis of these findings, it was assumed that all the performance management functions identified in the literature are important and could be implemented in the design of a performance management system. The results highlighted the importance of a performance plan and development plan to underpin the performance management system.
- Full Text:
- Date Issued: 2016
- Authors: Keshave, Hiten
- Date: 2016
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:863 , http://hdl.handle.net/10962/d1021180
- Description: This thesis begins with an introduction to performance management and the intended aim and objective of the research. Thereafter literature findings relative to performance management and performance management systems are discussed. In the review of literature, three processes that could be implemented in a performance management system were highlighted, namely; (1) the planning process, (2) the monitoring and development process, and (3) an annual summative and feedback process. Performance management functions deemed important to employees during each process of the performance management system were identified and discussed. Subsequent to the literature review, the research methodology was described and involved the implementation of quantitative research within a post-positivist paradigm in the form of a close-ended survey questionnaire. Analysis of the data involved a gap analysis and needs analysis. The gap analysis study was based on the opinion of management respondents in comparison to the opinion of non-management respondents. Results of the gap analysis were determined based on the calculation of an importance score for each sub-group. The needs analysis study was based on the overall opinion of all respondents, and results were determined based on the calculation of an overall importance score. In light of the literature review that was conducted to inform the questionnaire design, the survey results supported the literature review of each discussed performance management function with no evident contradictions. The results of the gap analysis and needs analysis were satisfactorily met for each performance management function. On the basis of these findings, it was assumed that all the performance management functions identified in the literature are important and could be implemented in the design of a performance management system. The results highlighted the importance of a performance plan and development plan to underpin the performance management system.
- Full Text:
- Date Issued: 2016
Investigating the impact of a psychometric assessment technique in the South African automotive industry
- Authors: Piro, Karen
- Date: 2011
- Subjects: Automobile industry and trade -- South Africa -- Employees -- Ability testing , Automobile industry and trade -- South Africa -- Employees -- Training of
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9397 , http://hdl.handle.net/10948/1381 , Automobile industry and trade -- South Africa -- Employees -- Ability testing , Automobile industry and trade -- South Africa -- Employees -- Training of
- Description: This research takes place in a South African multinational automotive industry, which needs to be on the forefront for being globally competitive and sustainable to remain viable in the country. A strategic initiative was embarked upon to identify talent within their staff population, through the psychometric assessment of learning potential. The objective was to identify high potential employees and provide them with the requisite training and development to meet the demands of the rapidly advancing technology. The primary purpose of this study is to investigate the usefulness of the Ability, Process of Information and Learning Battery (APIL) as a psychometric assessment tool for identifying talent, within a heterogeneous workforce. This research adopts a cross-cultural approach as it is comparative in nature and addresses the adequacy of a psychometric instrument in a multicultural context. The Employment Equity Act has transformed the landscape of the use of psychological measurement in South Africa, in that it stipulates that no psychological test that is biased against any cultural group can be used. A sample of 841 heterogeneous staff employees was assessed with three major research objectives: (a) to ensure that the instrument could stand scientific scrutiny thereby complying with the Employment Equity Act; (b) to recommend ways the organisation can identify and understand employees’ talent more holistically; and (c) to manage talent more effectively. The heterogeneous sample was divided into six homogeneous subsets for statistical analysis. This research attempted to answer the first objective through the examination of internal consistency, bias and equivalence of the APIL. Results showed good internal consistency, very good construct equivalence and low item bias, demonstrating the APIL can be applied fairly in a multicultural industrial setting. The second objective was determined by investigating whether significant difference in mean learning potential scores occur among the identified subsets in the sample. Statistical analyses provide clear trend lines indicating that sociopolitical and socioeconomic factors of advantagement and disadvantagement, age and education influence learning potential. However it is also evident that there are individuals across all subsets that demonstrate strong cognitive potential. This supports the rationale on which the APIL was developed, in that it distinguishes people with high learning potential despite the fact that there may be gaps or limitations in skill repertoire due to past disadvantagement. Recommendations to address the third objective is provided by aligning learning potential with the performance management system to provide a holistic overview of the talent composition. This will assist in the identifying of strategic training and development interventions needed at the individual, functional and organisational level, which is key for the South African automotive industry to remain competitive and viable.
- Full Text:
- Date Issued: 2011
- Authors: Piro, Karen
- Date: 2011
- Subjects: Automobile industry and trade -- South Africa -- Employees -- Ability testing , Automobile industry and trade -- South Africa -- Employees -- Training of
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9397 , http://hdl.handle.net/10948/1381 , Automobile industry and trade -- South Africa -- Employees -- Ability testing , Automobile industry and trade -- South Africa -- Employees -- Training of
- Description: This research takes place in a South African multinational automotive industry, which needs to be on the forefront for being globally competitive and sustainable to remain viable in the country. A strategic initiative was embarked upon to identify talent within their staff population, through the psychometric assessment of learning potential. The objective was to identify high potential employees and provide them with the requisite training and development to meet the demands of the rapidly advancing technology. The primary purpose of this study is to investigate the usefulness of the Ability, Process of Information and Learning Battery (APIL) as a psychometric assessment tool for identifying talent, within a heterogeneous workforce. This research adopts a cross-cultural approach as it is comparative in nature and addresses the adequacy of a psychometric instrument in a multicultural context. The Employment Equity Act has transformed the landscape of the use of psychological measurement in South Africa, in that it stipulates that no psychological test that is biased against any cultural group can be used. A sample of 841 heterogeneous staff employees was assessed with three major research objectives: (a) to ensure that the instrument could stand scientific scrutiny thereby complying with the Employment Equity Act; (b) to recommend ways the organisation can identify and understand employees’ talent more holistically; and (c) to manage talent more effectively. The heterogeneous sample was divided into six homogeneous subsets for statistical analysis. This research attempted to answer the first objective through the examination of internal consistency, bias and equivalence of the APIL. Results showed good internal consistency, very good construct equivalence and low item bias, demonstrating the APIL can be applied fairly in a multicultural industrial setting. The second objective was determined by investigating whether significant difference in mean learning potential scores occur among the identified subsets in the sample. Statistical analyses provide clear trend lines indicating that sociopolitical and socioeconomic factors of advantagement and disadvantagement, age and education influence learning potential. However it is also evident that there are individuals across all subsets that demonstrate strong cognitive potential. This supports the rationale on which the APIL was developed, in that it distinguishes people with high learning potential despite the fact that there may be gaps or limitations in skill repertoire due to past disadvantagement. Recommendations to address the third objective is provided by aligning learning potential with the performance management system to provide a holistic overview of the talent composition. This will assist in the identifying of strategic training and development interventions needed at the individual, functional and organisational level, which is key for the South African automotive industry to remain competitive and viable.
- Full Text:
- Date Issued: 2011
Journal development, scholar development and quality
- Rosenberg, Eureta, Togo, Muchaiteyi
- Authors: Rosenberg, Eureta , Togo, Muchaiteyi
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67314 , vital:29072 , https://doi.org/10.4314/SAJEE.V.33I1.1
- Description: publisher version , In reflecting on the contributions to Volume 33, it is evident that a variety of theories about learning and social change inform the scholars in environmental education, ranging from behaviourist, to social behavioural, constructivist and social constructivist learning theories, social and critical realism, and more. What unites these papers is a shared concern about learning in relation to the future well-being of the planet and its people. New scholars entering the field of environmental and sustainability education have the task of mastering not only the social– ecological subject matter of the field, but also their chosen learning theories. In this regard, drawing on the back copies of the SAJEE can be of great value. Much research and writing has already been done on curriculum, education and learning inside and outside of formal institutions, yet many more questions remain. The field is best advanced by noting and building on, challenging and advancing past studies and existing scholarship. The fact that all 33 Volumes of the SAJEE are available online, just a ‘few clicks away’ from any student or supervisor with Internet access, is therefore an enormous boon. We encourage readers and future authors to draw on the work in this and other environmental education journals as they conceptualise, design and reflect on their own studies.
- Full Text:
- Date Issued: 2017
- Authors: Rosenberg, Eureta , Togo, Muchaiteyi
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/67314 , vital:29072 , https://doi.org/10.4314/SAJEE.V.33I1.1
- Description: publisher version , In reflecting on the contributions to Volume 33, it is evident that a variety of theories about learning and social change inform the scholars in environmental education, ranging from behaviourist, to social behavioural, constructivist and social constructivist learning theories, social and critical realism, and more. What unites these papers is a shared concern about learning in relation to the future well-being of the planet and its people. New scholars entering the field of environmental and sustainability education have the task of mastering not only the social– ecological subject matter of the field, but also their chosen learning theories. In this regard, drawing on the back copies of the SAJEE can be of great value. Much research and writing has already been done on curriculum, education and learning inside and outside of formal institutions, yet many more questions remain. The field is best advanced by noting and building on, challenging and advancing past studies and existing scholarship. The fact that all 33 Volumes of the SAJEE are available online, just a ‘few clicks away’ from any student or supervisor with Internet access, is therefore an enormous boon. We encourage readers and future authors to draw on the work in this and other environmental education journals as they conceptualise, design and reflect on their own studies.
- Full Text:
- Date Issued: 2017
Developmental and reproductive performance of a specialist herbivore depend on seasonality of, and light conditions experienced by, the host plant
- Zachariades, Uyi O O,, Heshula, L U P, Hill, Martin P
- Authors: Zachariades, Uyi O O, , Heshula, L U P , Hill, Martin P
- Date: 2018
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59845 , vital:27667 , https://doi.org/10.1371/journal.pone.0190700
- Description: Host plant phenology (as influenced by seasonality) and light-mediated changes in the phenotypic and phytochemical properties of leaves have been hypothesised to equivocally influence insect herbivore performance. Here, we examined the effects of seasonality, through host plant phenology (late growth-season = autumn vs flowering-season = winter) and light environment (shade vs full-sun habitat) on the leaf characteristics of the invasive alien plant, Chromolaena odorata. In addition, the performance of a specialist folivore, Pareuchaetes insulata, feeding on leaves obtained from both shaded and full-sun habitats during autumn and winter, was evaluated over two generations. Foliar nitrogen and magnesium contents were generally higher in shaded plants with much higher levels during winter. Leaf water content was higher in shaded and in autumn plants. Total non-structural carbohydrate (TNC) and phosphorus contents did not differ as a function of season, but were higher in shaded foliage compared to full-sun leaves. Leaf toughness was noticeably higher on plants growing in full-sun during winter. With the exception of shaded leaves in autumn that supported the best performance [fastest development, heaviest pupal mass, and highest growth rate and Host Suitability Index (HSI) score], full-sun foliage in autumn surprisingly also supported an improved performance of the moth compared to shaded or full-sun leaves in winter. Our findings suggest that shaded and autumn foliage are nutritionally more suitable for the growth and reproduction of P. insulata. However, the heavier pupal mass, increased number of eggs and higher HSI score in individuals that fed on full-sun foliage in autumn compared to their counterparts that fed on shaded or full-sun foliage in winter suggest that full-sun foliage during autumn is also a suitable food source for larvae of the moth. In sum, our study demonstrates that seasonal and light-modulated changes in leaf characteristics can affect insect folivore performance in ways that are not linear.
- Full Text:
- Date Issued: 2018
- Authors: Zachariades, Uyi O O, , Heshula, L U P , Hill, Martin P
- Date: 2018
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59845 , vital:27667 , https://doi.org/10.1371/journal.pone.0190700
- Description: Host plant phenology (as influenced by seasonality) and light-mediated changes in the phenotypic and phytochemical properties of leaves have been hypothesised to equivocally influence insect herbivore performance. Here, we examined the effects of seasonality, through host plant phenology (late growth-season = autumn vs flowering-season = winter) and light environment (shade vs full-sun habitat) on the leaf characteristics of the invasive alien plant, Chromolaena odorata. In addition, the performance of a specialist folivore, Pareuchaetes insulata, feeding on leaves obtained from both shaded and full-sun habitats during autumn and winter, was evaluated over two generations. Foliar nitrogen and magnesium contents were generally higher in shaded plants with much higher levels during winter. Leaf water content was higher in shaded and in autumn plants. Total non-structural carbohydrate (TNC) and phosphorus contents did not differ as a function of season, but were higher in shaded foliage compared to full-sun leaves. Leaf toughness was noticeably higher on plants growing in full-sun during winter. With the exception of shaded leaves in autumn that supported the best performance [fastest development, heaviest pupal mass, and highest growth rate and Host Suitability Index (HSI) score], full-sun foliage in autumn surprisingly also supported an improved performance of the moth compared to shaded or full-sun leaves in winter. Our findings suggest that shaded and autumn foliage are nutritionally more suitable for the growth and reproduction of P. insulata. However, the heavier pupal mass, increased number of eggs and higher HSI score in individuals that fed on full-sun foliage in autumn compared to their counterparts that fed on shaded or full-sun foliage in winter suggest that full-sun foliage during autumn is also a suitable food source for larvae of the moth. In sum, our study demonstrates that seasonal and light-modulated changes in leaf characteristics can affect insect folivore performance in ways that are not linear.
- Full Text:
- Date Issued: 2018
An analysis of the perceptions of non-bargaining unit employees of the performance management system at Transnet Engineering
- Authors: Nel, Nico
- Date: 2014
- Subjects: Performance -- Management , Performance standards -- South Africa , Collective bargaining unit -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/5531 , vital:20874
- Description: Transnet is facing challenging market realities and a competitive operating environment. Performance management has been emphasised as a critical tool to guide Transnet in maintaining a competitive advantage. Performance management cannot be viewed in isolation from the organisational context and is inextricably linked to the Human Resources strategy, which in turn is aligned with the overall business strategy. Performance management may be defined as a systematic process by which an organisation involves its employees, as individuals and members of groups, in improving organisational effectiveness in the accomplishment of organisational mission and goals. For the purposes of this study, performance management was explored in terms of purpose, key role players, processes, criteria and challenges. The main research problem of this study was to determine the perceptions of non-bargaining unit employees of the performance management system at Transnet Engineering. The main research problem had three sub-problems which were addressed through the following actions: A literature study was conducted highlighting the importance of an effective performance management system which establishes a foundation for rewarding excellence by aligning individual objectives with organisational mission and objectives. In this way, performance management establishes clear expectations in terms of results, actions and behaviours. Through regular feedback and coaching, performance management provides a mechanism for detecting problems at an early stage and identifies ways in which to take corrective action. Perceptions of performance management are largely centred around fairness, and dependent on a number of issues, including openness, transparency, communication, and equitability, and the establishment of clear parameters of measurement such as whether both skill and effort will be evaluated. This is why it is important to link performance appraisals to employee goals. If mutually negotiated goals, which involve the participation of all stakeholders, are established at the beginning of the performance period and there is on-going feedback to employees about their performance, then performance appraisals may be perceived as objective, fair and reliable. The insights gained from the literature survey were incorporated into a survey questionnaire which was used in the empirical study to investigate the perceptions of non-bargaining unit employees of the performance management system at Transnet Engineering. This study revealed that most of the respondents were not satisfied with the performance management system within Transnet Engineering, that performance management could be enhanced by using multiple measures more frequently and that greater involvement of subordinates at each step in the performance management process would lead to a greater level of acceptance thereof.
- Full Text:
- Date Issued: 2014
- Authors: Nel, Nico
- Date: 2014
- Subjects: Performance -- Management , Performance standards -- South Africa , Collective bargaining unit -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/5531 , vital:20874
- Description: Transnet is facing challenging market realities and a competitive operating environment. Performance management has been emphasised as a critical tool to guide Transnet in maintaining a competitive advantage. Performance management cannot be viewed in isolation from the organisational context and is inextricably linked to the Human Resources strategy, which in turn is aligned with the overall business strategy. Performance management may be defined as a systematic process by which an organisation involves its employees, as individuals and members of groups, in improving organisational effectiveness in the accomplishment of organisational mission and goals. For the purposes of this study, performance management was explored in terms of purpose, key role players, processes, criteria and challenges. The main research problem of this study was to determine the perceptions of non-bargaining unit employees of the performance management system at Transnet Engineering. The main research problem had three sub-problems which were addressed through the following actions: A literature study was conducted highlighting the importance of an effective performance management system which establishes a foundation for rewarding excellence by aligning individual objectives with organisational mission and objectives. In this way, performance management establishes clear expectations in terms of results, actions and behaviours. Through regular feedback and coaching, performance management provides a mechanism for detecting problems at an early stage and identifies ways in which to take corrective action. Perceptions of performance management are largely centred around fairness, and dependent on a number of issues, including openness, transparency, communication, and equitability, and the establishment of clear parameters of measurement such as whether both skill and effort will be evaluated. This is why it is important to link performance appraisals to employee goals. If mutually negotiated goals, which involve the participation of all stakeholders, are established at the beginning of the performance period and there is on-going feedback to employees about their performance, then performance appraisals may be perceived as objective, fair and reliable. The insights gained from the literature survey were incorporated into a survey questionnaire which was used in the empirical study to investigate the perceptions of non-bargaining unit employees of the performance management system at Transnet Engineering. This study revealed that most of the respondents were not satisfied with the performance management system within Transnet Engineering, that performance management could be enhanced by using multiple measures more frequently and that greater involvement of subordinates at each step in the performance management process would lead to a greater level of acceptance thereof.
- Full Text:
- Date Issued: 2014
Development of antibiotic loaded liposomal hydrocolloid dressings for application in wound healing
- Authors: Ntsalu, Vuyiseka
- Date: 2017
- Subjects: Wound healing -- South Africa Liposomes Hydrocolloid surgical dressings -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/13957 , vital:27361
- Description: Wound healing, as a normal biological process in the human body, is achieved through four precise and highly programmed phases: hemostasis, inflammation, proliferation, and remodeling. For a wound to heal successfully, all four phases must occur in the proper sequence and time frame. However, many factors can interfere with one or more of these phases, thus causing improper or impaired wound healing. Maintaining a moist wound environment is crucial in facilitating the wound-healing process. The beneficial effects of a moist versus a dry wound environment include re-epithelization, tissue granulation, and repair. The use of hydrocolloid occlusive dressings in maintaining a moist wound environment has proven to be a useful adjunct in facilitating wound healing. Although hydrocolloid dressings have been widely used clinically in wound management, bacterial resistance, poor solubility and sustained drug release remain to be a problem for many of the drugs used in wound therapy. In chronic wound management, where patients normally undergo long treatments and frequent dressing changes, a system that delivers drugs into a wound site in a controlled fashion can improve patient compliance and therapeutic outcomes. Liposomes are small phospholipid vesicles that have been widely investigated as drug carriers for the delivery of therapeutic agents. They are spherical lipid vesicles consisting of phospholipid bilayers that improve the efficacy of the drugs by fusing with biological membranes, and eventually releasing their entrapped content into the cells or bacteria. The aim of this study therefore, is to develop a new bacitracin-based controlled release hydrocolloid dressing, with good absorptive properties for improving the efficacy of antibiotics in wound healing. HPLC (high-pressure liquid chromatography) assay of bacitracin was performed for quantification of the drug. Liposomes were prepared using thin film hydration and extrusion methods. Liposomes were also characterized based on their ideal particle size and encapsulation efficiency, and then incorporated into the different ratios of chitosan/gelatin hydrocolloid films. The films were prepared with increase in gelatin concentration and were evaluated for folding endurance, tensile strength, water absorption capacity, morphology, drug release kinetics, antimicrobial activity and stability. The morphology of these films was found to be very smooth and homogeneous proving a good compatibility between the two polymers. With increase in gelatin concentration, folding endurance, water absorption capacity, tensile strength, drug release kinetics and antimicrobial activity were increased. The antibacterial activity against various bacterial species was improved in the bacitracin loaded hydrocolloid films as compared to the blank films. Based on the findings above, it can be concluded that chitosan/gelatin films at 1:3 proportion is a successful wound dressing for wound management with improved wound healing properties than other formulations. This formulation is a potential candidate for the development of alternative pharmaceutical dosage forms, for the treatment of bacterial infected wounds, based on the activity of the eco-friendly chitosan matrix added to the bacitracin activity. In this work, chitosan also demonstrated a great potential as a dressing for advanced wound therapy and confirmed its good biocompatibility and potential to provide, in combination with liposomes, sustained drug release which is highly beneficial for wound treatment. The addition of gelatin improved the water affinity of the films and facilitated water mediated cross-linking process.
- Full Text:
- Date Issued: 2017
- Authors: Ntsalu, Vuyiseka
- Date: 2017
- Subjects: Wound healing -- South Africa Liposomes Hydrocolloid surgical dressings -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/13957 , vital:27361
- Description: Wound healing, as a normal biological process in the human body, is achieved through four precise and highly programmed phases: hemostasis, inflammation, proliferation, and remodeling. For a wound to heal successfully, all four phases must occur in the proper sequence and time frame. However, many factors can interfere with one or more of these phases, thus causing improper or impaired wound healing. Maintaining a moist wound environment is crucial in facilitating the wound-healing process. The beneficial effects of a moist versus a dry wound environment include re-epithelization, tissue granulation, and repair. The use of hydrocolloid occlusive dressings in maintaining a moist wound environment has proven to be a useful adjunct in facilitating wound healing. Although hydrocolloid dressings have been widely used clinically in wound management, bacterial resistance, poor solubility and sustained drug release remain to be a problem for many of the drugs used in wound therapy. In chronic wound management, where patients normally undergo long treatments and frequent dressing changes, a system that delivers drugs into a wound site in a controlled fashion can improve patient compliance and therapeutic outcomes. Liposomes are small phospholipid vesicles that have been widely investigated as drug carriers for the delivery of therapeutic agents. They are spherical lipid vesicles consisting of phospholipid bilayers that improve the efficacy of the drugs by fusing with biological membranes, and eventually releasing their entrapped content into the cells or bacteria. The aim of this study therefore, is to develop a new bacitracin-based controlled release hydrocolloid dressing, with good absorptive properties for improving the efficacy of antibiotics in wound healing. HPLC (high-pressure liquid chromatography) assay of bacitracin was performed for quantification of the drug. Liposomes were prepared using thin film hydration and extrusion methods. Liposomes were also characterized based on their ideal particle size and encapsulation efficiency, and then incorporated into the different ratios of chitosan/gelatin hydrocolloid films. The films were prepared with increase in gelatin concentration and were evaluated for folding endurance, tensile strength, water absorption capacity, morphology, drug release kinetics, antimicrobial activity and stability. The morphology of these films was found to be very smooth and homogeneous proving a good compatibility between the two polymers. With increase in gelatin concentration, folding endurance, water absorption capacity, tensile strength, drug release kinetics and antimicrobial activity were increased. The antibacterial activity against various bacterial species was improved in the bacitracin loaded hydrocolloid films as compared to the blank films. Based on the findings above, it can be concluded that chitosan/gelatin films at 1:3 proportion is a successful wound dressing for wound management with improved wound healing properties than other formulations. This formulation is a potential candidate for the development of alternative pharmaceutical dosage forms, for the treatment of bacterial infected wounds, based on the activity of the eco-friendly chitosan matrix added to the bacitracin activity. In this work, chitosan also demonstrated a great potential as a dressing for advanced wound therapy and confirmed its good biocompatibility and potential to provide, in combination with liposomes, sustained drug release which is highly beneficial for wound treatment. The addition of gelatin improved the water affinity of the films and facilitated water mediated cross-linking process.
- Full Text:
- Date Issued: 2017
Photocatalytic activity and antibacterial properties of Ag/N-doped TiO2 nanoparticles on PVAE-CS nanofibre support
- Authors: Ocwelwang, Atsile Rosy
- Date: 2012
- Subjects: Nanocomposites (Materials) , Nanofibers , Electrospinning
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11337 , http://hdl.handle.net/10353/d1006794 , Nanocomposites (Materials) , Nanofibers , Electrospinning
- Description: Lack of potable water is one of the major challenges that the world faces currently and the effects of this are mainly experienced by people in developing countries. This has therefore propelled research in advanced oxidation technologies AOTs to improve the current water treatment methods using cost effective, non toxic and efficient treatment methods. Hence, in this study the sol-gel synthesis method was used to prepare TiO2 nanoparticles that were photocatalytically active under UV and visible solar light as well as possessing antibacterial properties. Silver and nitrogen doping was carried out to extend the optical absorption of TiO2. For easy removal and reuse of the photocatalyst the nanoparticles were immobilized on chitosan and poly (vinyl-alcohol-co-ethylene) using the electrospining technique. The synthesized nanomaterials were characterized by FTIR, XRD, SEM/EDS, TEM, DRS, and TGA. FTIR and EDS analysis confirmed the formation and composition of TiO2 nanopowders for the doped and undoped nanoparticles. XRD analysis showed that the anatase phase was the dominant crystalline phase of the synthesized nanopowders. SEM and TEM respectively illustrated the distribution and size of the electrospun nanofibers and the nanoparticles of TiO2. DRS results showed that there was a significant shift in the absorption band edge and wavelength of Ag-TiO2 to 397 nm, followed by N-TiO2 at 396 nm compared to the commercial titania which was at 359 nm. The photocatalytic activities and antibacterial properties of these materials were tested on methylene blue dye and E.coli microorganism respectively. Ag-TiO2 immobilized on nanofibers of chitosan and PVAE had the highest photocatalytic activity compared to N-TiO2. Similar results were observed when the biocide properties of these materials were tested on E. coli.
- Full Text:
- Date Issued: 2012
- Authors: Ocwelwang, Atsile Rosy
- Date: 2012
- Subjects: Nanocomposites (Materials) , Nanofibers , Electrospinning
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11337 , http://hdl.handle.net/10353/d1006794 , Nanocomposites (Materials) , Nanofibers , Electrospinning
- Description: Lack of potable water is one of the major challenges that the world faces currently and the effects of this are mainly experienced by people in developing countries. This has therefore propelled research in advanced oxidation technologies AOTs to improve the current water treatment methods using cost effective, non toxic and efficient treatment methods. Hence, in this study the sol-gel synthesis method was used to prepare TiO2 nanoparticles that were photocatalytically active under UV and visible solar light as well as possessing antibacterial properties. Silver and nitrogen doping was carried out to extend the optical absorption of TiO2. For easy removal and reuse of the photocatalyst the nanoparticles were immobilized on chitosan and poly (vinyl-alcohol-co-ethylene) using the electrospining technique. The synthesized nanomaterials were characterized by FTIR, XRD, SEM/EDS, TEM, DRS, and TGA. FTIR and EDS analysis confirmed the formation and composition of TiO2 nanopowders for the doped and undoped nanoparticles. XRD analysis showed that the anatase phase was the dominant crystalline phase of the synthesized nanopowders. SEM and TEM respectively illustrated the distribution and size of the electrospun nanofibers and the nanoparticles of TiO2. DRS results showed that there was a significant shift in the absorption band edge and wavelength of Ag-TiO2 to 397 nm, followed by N-TiO2 at 396 nm compared to the commercial titania which was at 359 nm. The photocatalytic activities and antibacterial properties of these materials were tested on methylene blue dye and E.coli microorganism respectively. Ag-TiO2 immobilized on nanofibers of chitosan and PVAE had the highest photocatalytic activity compared to N-TiO2. Similar results were observed when the biocide properties of these materials were tested on E. coli.
- Full Text:
- Date Issued: 2012
Synthesis, characterisation and evaluation of benzoxaborole-based hybrids as antiplasmodial agents
- Authors: Gumbo, Maureen
- Date: 2017
- Subjects: Malaria Chemotherapy , Antimalarials , Boron compounds , Drug resistance , Plasmodium falciparum , Drug development
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/59193 , vital:27456
- Description: Malaria is a mosquito-borne disease, which continues to pose a threat to the entire humanity. About 40% of the world population is estimated to be at risk of infections by malaria. Despite efforts undertaken by scientific community, government entities and international organizations, malaria is still rampant. The major problem is drug resistance, where the Plasmodium spp have over the past decades developed drug resistance against available drugs. In order to counter this problem, novel antimalarial drugs that are efficacious and with novel mode of action are of great necessity. Benzoxaborole derivatives have been shown to exhibit promising antimalarial activity against Plasmodium falciparum strains. Previous studies reported on the compounds such as 6-(2- (alkoxycarbonyl)pyrazinyl-5-oxy)-1,3-dihydro-1-hydroxy-2,1-benzoxaboroles, which showed good antimalarial activity against both W7 and 3D7 strains without significant toxicity. On the other hand, chloroquine (CQ) and cinnamic acids have a wide variety of biological activity including antimalarial activity. Herein, a hybridisation strategy was employed to synthesise new CQ-benzoxaborole and cinnamoyl-benzoxaborole hybrids. CQ-Benzoxaborole 2.12a-c and cinnamoylbenzoxaborole 2.11a-g hydrid molecules were synthesised in low to good yields. Their structural identities were confirmed using conventional spectroscopic techniques (1H and 13C NMR, and mass spectrometry). CQ-benzoxaborole compounds, however, showed instability, and only 2.12b was used for in vitro biological assay and showed activity comparable to CQ. Furthermore, in vitro biological assay revealed that compounds 2.11a-g poorly inhibited the growth of P. falciparum parasites. Interestingly, these compounds, however, exhibited satisfactory activity against Trypanosoma brucei with IC50 = 0.052 μM for compound 2.11g. The cell cytotoxicity assay of all final compounds confirmed that all CQ-benzoxaborole 2.12b and cinnamoyl-benzoxaborole 2.11a-g hybrids were non-toxic against HeLa cell lines. However, efforts to further expand the structure-activity relationship (SAR) of CQbenzoxaborole by increasing the length of the linker with one extra carbon (Scheme 2.10) were not possible as an important precursor 6-formylbenzoxaborole 2.29 could not be synthesized in sufficient yields. , Thesis (MSc) -- Faculty of Faculty of Science, Chemistry, 2017
- Full Text:
- Date Issued: 2017
- Authors: Gumbo, Maureen
- Date: 2017
- Subjects: Malaria Chemotherapy , Antimalarials , Boron compounds , Drug resistance , Plasmodium falciparum , Drug development
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/59193 , vital:27456
- Description: Malaria is a mosquito-borne disease, which continues to pose a threat to the entire humanity. About 40% of the world population is estimated to be at risk of infections by malaria. Despite efforts undertaken by scientific community, government entities and international organizations, malaria is still rampant. The major problem is drug resistance, where the Plasmodium spp have over the past decades developed drug resistance against available drugs. In order to counter this problem, novel antimalarial drugs that are efficacious and with novel mode of action are of great necessity. Benzoxaborole derivatives have been shown to exhibit promising antimalarial activity against Plasmodium falciparum strains. Previous studies reported on the compounds such as 6-(2- (alkoxycarbonyl)pyrazinyl-5-oxy)-1,3-dihydro-1-hydroxy-2,1-benzoxaboroles, which showed good antimalarial activity against both W7 and 3D7 strains without significant toxicity. On the other hand, chloroquine (CQ) and cinnamic acids have a wide variety of biological activity including antimalarial activity. Herein, a hybridisation strategy was employed to synthesise new CQ-benzoxaborole and cinnamoyl-benzoxaborole hybrids. CQ-Benzoxaborole 2.12a-c and cinnamoylbenzoxaborole 2.11a-g hydrid molecules were synthesised in low to good yields. Their structural identities were confirmed using conventional spectroscopic techniques (1H and 13C NMR, and mass spectrometry). CQ-benzoxaborole compounds, however, showed instability, and only 2.12b was used for in vitro biological assay and showed activity comparable to CQ. Furthermore, in vitro biological assay revealed that compounds 2.11a-g poorly inhibited the growth of P. falciparum parasites. Interestingly, these compounds, however, exhibited satisfactory activity against Trypanosoma brucei with IC50 = 0.052 μM for compound 2.11g. The cell cytotoxicity assay of all final compounds confirmed that all CQ-benzoxaborole 2.12b and cinnamoyl-benzoxaborole 2.11a-g hybrids were non-toxic against HeLa cell lines. However, efforts to further expand the structure-activity relationship (SAR) of CQbenzoxaborole by increasing the length of the linker with one extra carbon (Scheme 2.10) were not possible as an important precursor 6-formylbenzoxaborole 2.29 could not be synthesized in sufficient yields. , Thesis (MSc) -- Faculty of Faculty of Science, Chemistry, 2017
- Full Text:
- Date Issued: 2017
Generation of a virtual library of terpenes using graph theory, and its application in exploration of the mechanisms of terpene biosynthesis
- Authors: Dendera, Washington
- Date: 2020
- Subjects: Terpenes , Plants -- Metabolism , Computational biology , Bioinformatics , Organic compounds -- Synthesis , Monoterpenes , Molecular biology -- Computer simulation
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/123453 , vital:35439
- Description: Terpenes form a large group of organic compounds which have proven to be of use to many living organisms being used by plants for metabolism (Pichersky and Gershenzon, 1934; McGarvey and Croteau, 1995; Gershenzon and Dudareva, 2007), defence or as a means to attract pollinators and also used by humans in medical, pharmaceutical and food industry (Bicas, Dionísio and Pastore, 2009; Marmulla and Harder, 2014; Kandi et al., 2015). Following on literature methods to generate chemical libraries using graph theoretic techniques, complete libraries of all possible terpene isomers have been constructed with the goal of construction of derivative libraries of possible carbocation intermediates which are important in the elucidation of mechanisms in the biosynthesis of terpenes. Virtual library generation of monoterpenes was first achieved by generating graphs of order 7, 8, 9 and 10 using the Nauty and Traces suite. These were screened and processed with a set of collated Python scripts written to recognize the graphs in text format and translate them to molecules, minimizing through Tinker whilst discarding graphs that violate chemistry laws. As a result of the computational time required only order 7 and order 10 graphs were processed. Out of the 873 graphs generated from order seven, 353 were converted to molecules and from the 11,7 million produced from order 10 half were processed resulting in the production of 442928 compounds (repeats included). For screening, 55 366 compounds were docked in the active site of limonene synthase; of these 2355 ligands had a good Vina docking score with a binding energy of between -7.0 and -7.4 kcal.mol-1. When these best docked molecules were overlaid in the active site a map of possible ligand positions within the active site of limonene synthase was traced out.
- Full Text:
- Date Issued: 2020
- Authors: Dendera, Washington
- Date: 2020
- Subjects: Terpenes , Plants -- Metabolism , Computational biology , Bioinformatics , Organic compounds -- Synthesis , Monoterpenes , Molecular biology -- Computer simulation
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/123453 , vital:35439
- Description: Terpenes form a large group of organic compounds which have proven to be of use to many living organisms being used by plants for metabolism (Pichersky and Gershenzon, 1934; McGarvey and Croteau, 1995; Gershenzon and Dudareva, 2007), defence or as a means to attract pollinators and also used by humans in medical, pharmaceutical and food industry (Bicas, Dionísio and Pastore, 2009; Marmulla and Harder, 2014; Kandi et al., 2015). Following on literature methods to generate chemical libraries using graph theoretic techniques, complete libraries of all possible terpene isomers have been constructed with the goal of construction of derivative libraries of possible carbocation intermediates which are important in the elucidation of mechanisms in the biosynthesis of terpenes. Virtual library generation of monoterpenes was first achieved by generating graphs of order 7, 8, 9 and 10 using the Nauty and Traces suite. These were screened and processed with a set of collated Python scripts written to recognize the graphs in text format and translate them to molecules, minimizing through Tinker whilst discarding graphs that violate chemistry laws. As a result of the computational time required only order 7 and order 10 graphs were processed. Out of the 873 graphs generated from order seven, 353 were converted to molecules and from the 11,7 million produced from order 10 half were processed resulting in the production of 442928 compounds (repeats included). For screening, 55 366 compounds were docked in the active site of limonene synthase; of these 2355 ligands had a good Vina docking score with a binding energy of between -7.0 and -7.4 kcal.mol-1. When these best docked molecules were overlaid in the active site a map of possible ligand positions within the active site of limonene synthase was traced out.
- Full Text:
- Date Issued: 2020
Synthesis of silver nanoparticles and their role against human and Plasmodium falciparum leucine aminopeptidase
- Authors: Mnkandhla, Dumisani
- Date: 2015
- Subjects: Silver , Nanoparticles , Plasmodium falciparum , Leucine aminopeptidase , Antimalarials , Nanotechnology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4150 , http://hdl.handle.net/10962/d1017911
- Description: Antimalarial drug discovery remains a challenging endeavour as malaria parasites continue to develop resistance to drugs, including those which are currently the last line of defence against the disease. Plasmodium falciparum is the most virulent of the malaria parasites and it delivers its deadliest impact during the erythrocytic stages of the parasite’s life cycle; a stage characterised by elevated catabolism of haemoglobin and anabolism of parasite proteins. The present study investigates the use of nanotechnology in the form of metallic silver nanoparticles (AgNPs) against P. falciparum leucine aminopeptidase (PfLAP), a validated biomedical target involved in haemoglobin metabolism. AgNPs were also tested against the human homolog cytosolic Homo sapiens leucine aminopeptidase (HsLAP) to ascertain their selective abilities. PfLAP and HsLAP were successfully expressed in Escherichia coli BL21(DE3) cells. PfLAP showed optimal thermal stability at 25 °C and optimal pH stability at pH 8.0 with a Km of 42.7 mM towards leucine-p-nitroanilide (LpNA) and a Vmax of 59.9 μmol.ml⁻¹.min⁻¹. HsLAP was optimally stable at 37 °C and at pH 7.0 with a Km of 16.7 mM and a Vmax of 17.2 μmol.ml⁻¹.min⁻¹. Both enzymes exhibited optimal activity in the presence of 2 mM Mn²⁺. On interaction with polyvinylpyrrolidone (PVP) stabilised AgNPs, both enzymes were inhibited to differing extents with PfLAP losing three fold of its catalytic efficiency relative to HsLAP. These results show the ability of AgNPs to selectively inhibit PfLAP whilst having much lesser effects on its human homolog. With the use of available targeting techniques, the present study shows the potential use of nanotechnology based approaches as “silver bullets” that can target PfLAP without adversely affecting the host. However further research needs to be conducted to better understand the mechanisms of AgNP action, drug targeting and the health and safety issues associated with nanotechnology use.
- Full Text:
- Date Issued: 2015
- Authors: Mnkandhla, Dumisani
- Date: 2015
- Subjects: Silver , Nanoparticles , Plasmodium falciparum , Leucine aminopeptidase , Antimalarials , Nanotechnology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4150 , http://hdl.handle.net/10962/d1017911
- Description: Antimalarial drug discovery remains a challenging endeavour as malaria parasites continue to develop resistance to drugs, including those which are currently the last line of defence against the disease. Plasmodium falciparum is the most virulent of the malaria parasites and it delivers its deadliest impact during the erythrocytic stages of the parasite’s life cycle; a stage characterised by elevated catabolism of haemoglobin and anabolism of parasite proteins. The present study investigates the use of nanotechnology in the form of metallic silver nanoparticles (AgNPs) against P. falciparum leucine aminopeptidase (PfLAP), a validated biomedical target involved in haemoglobin metabolism. AgNPs were also tested against the human homolog cytosolic Homo sapiens leucine aminopeptidase (HsLAP) to ascertain their selective abilities. PfLAP and HsLAP were successfully expressed in Escherichia coli BL21(DE3) cells. PfLAP showed optimal thermal stability at 25 °C and optimal pH stability at pH 8.0 with a Km of 42.7 mM towards leucine-p-nitroanilide (LpNA) and a Vmax of 59.9 μmol.ml⁻¹.min⁻¹. HsLAP was optimally stable at 37 °C and at pH 7.0 with a Km of 16.7 mM and a Vmax of 17.2 μmol.ml⁻¹.min⁻¹. Both enzymes exhibited optimal activity in the presence of 2 mM Mn²⁺. On interaction with polyvinylpyrrolidone (PVP) stabilised AgNPs, both enzymes were inhibited to differing extents with PfLAP losing three fold of its catalytic efficiency relative to HsLAP. These results show the ability of AgNPs to selectively inhibit PfLAP whilst having much lesser effects on its human homolog. With the use of available targeting techniques, the present study shows the potential use of nanotechnology based approaches as “silver bullets” that can target PfLAP without adversely affecting the host. However further research needs to be conducted to better understand the mechanisms of AgNP action, drug targeting and the health and safety issues associated with nanotechnology use.
- Full Text:
- Date Issued: 2015
Synthesis, characterisation and evaluation of novel ferrocene-thiazole derivatives as antiplasmodial agents
- Authors: Hakizimana, Emmanuel Victor
- Date: 2017
- Subjects: Plasmodium , Malaria -- Chemotherapy , Plasmodium falciparum , Plasmodium -- Inhibitors , Drug resistance in microorganisms , Thiaszoles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/96068 , vital:31232
- Description: Malaria is mosquito-transmitted disease which continues to pose threat to humanity, despite the efforts undertaken by the scientific community, government entities and international organizations. The major problem is that Plasmodium species have developed resistance against available drugs. In order to counter this problem, antimalarial drugs that are efficacious and with novel mode of action are of great necessity. Thiazole derivatives, in particular aminomethylthiazole analogues, have been shown to exhibit promising antimalarial activity against Plasmodium falciparum strains. Previous studies reported the hit compound MMV010539, which showed good antimalarial activity against both K1 (CQ and multidrug resistant strains) and NF54 (CQ sensitive strain). In this study, MMV010539 was deemed to be as an attractive compound to generate novel analogues by addition of ferrocenyl organometallic unit. The ferrocene based compounds have shown biological activity; and with ferroquine currently in clinical trials there has been increasing research into identifying new ferrocenyl-containing molecules as potential antimalarial agents. Herein, thiazole ferrocene based molecules 3.22a-e were synthesised in low to good yields. Their structural identities were confirmed using conventional spectroscopic techniques (¹H and ¹³C NMR, FT-IR spectroscopy and mass spectrometry). The cell cytotoxicity assay of all final compounds confirmed that all ferrocene-thiazole blends 3.22a-e were non-toxic against HeLa cell lines. However, the in vitro biological assay revealed that despite the absence of cell cytotoxicity these compounds poorly inhibited the growth of Plasmodium falciparum parasite. As the aim was to expand further the structure-activity relationship (SAR) of MMV010539, this study confirmed the previous findings that there is a limited structural modification that could be accommodated as indicated in Figure 3.3 (Panel C). Moreover, the combination of ferrocenyl moiety and various alkylamines resulted in compounds with poor antiplasmodial potency, further suggesting that the free amine (Panel A, Figure 3.3) is important for activity.
- Full Text:
- Date Issued: 2017
- Authors: Hakizimana, Emmanuel Victor
- Date: 2017
- Subjects: Plasmodium , Malaria -- Chemotherapy , Plasmodium falciparum , Plasmodium -- Inhibitors , Drug resistance in microorganisms , Thiaszoles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/96068 , vital:31232
- Description: Malaria is mosquito-transmitted disease which continues to pose threat to humanity, despite the efforts undertaken by the scientific community, government entities and international organizations. The major problem is that Plasmodium species have developed resistance against available drugs. In order to counter this problem, antimalarial drugs that are efficacious and with novel mode of action are of great necessity. Thiazole derivatives, in particular aminomethylthiazole analogues, have been shown to exhibit promising antimalarial activity against Plasmodium falciparum strains. Previous studies reported the hit compound MMV010539, which showed good antimalarial activity against both K1 (CQ and multidrug resistant strains) and NF54 (CQ sensitive strain). In this study, MMV010539 was deemed to be as an attractive compound to generate novel analogues by addition of ferrocenyl organometallic unit. The ferrocene based compounds have shown biological activity; and with ferroquine currently in clinical trials there has been increasing research into identifying new ferrocenyl-containing molecules as potential antimalarial agents. Herein, thiazole ferrocene based molecules 3.22a-e were synthesised in low to good yields. Their structural identities were confirmed using conventional spectroscopic techniques (¹H and ¹³C NMR, FT-IR spectroscopy and mass spectrometry). The cell cytotoxicity assay of all final compounds confirmed that all ferrocene-thiazole blends 3.22a-e were non-toxic against HeLa cell lines. However, the in vitro biological assay revealed that despite the absence of cell cytotoxicity these compounds poorly inhibited the growth of Plasmodium falciparum parasite. As the aim was to expand further the structure-activity relationship (SAR) of MMV010539, this study confirmed the previous findings that there is a limited structural modification that could be accommodated as indicated in Figure 3.3 (Panel C). Moreover, the combination of ferrocenyl moiety and various alkylamines resulted in compounds with poor antiplasmodial potency, further suggesting that the free amine (Panel A, Figure 3.3) is important for activity.
- Full Text:
- Date Issued: 2017
Ectomycorrhizal fungal assessment of South African Pinus patula seedlings and their biological control potential to enhance seedling growth
- FitzGerald, Véronique Chartier
- Authors: FitzGerald, Véronique Chartier
- Date: 2019
- Subjects: Ectomycorrhizal fungi , Pinus patula Diseases and pests Biological control South Africa , Fusarium , Forest nurseries , Seedlings Growth , Seedlings Diseases and pests
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/67902 , vital:29167
- Description: The South Africa forestry industry, covering 1.3 million hectares, is dependent on exotic pine and eucalyptus species. Nursery seedlings are not inoculated with ectomycorrhizal (ECM) fungi or other beneficial microbes. Fusarium circinatum is an economically important pathogen affecting seedling survival. The purpose of this investigation was to assess levels of naturally occurring ECM colonisation in South African nurseries and to determine the effects of seedling inoculation with selected ECM and bacterial isolates on plant growth and resistance to the fungal pathogen F. circiantum. Pinus patula seedlings from 10 different South African nurseries were assessed for ECM colonisation using a grid line intersect method and molecularly identified using morphological and next-generation Illumina sequencing. Explants from ECM basidiocarps, collected from Pinus stands, were plated onto MMN medium to obtain isolates which were verified using molecular techniques. Mycorrhizal helper bacteria (MHB) were also isolated from these basiocarps, tested for MHB properties, siderophore production, phospahte solubilising and IAA production. ECM and associated bacterial isolates were used to inoculate seedlings and growth was assessed over a 5 month period. Colonisation of seedlings in production nurseries was low (2-21%). Morphologically the ECM fungi T. terrestris, Suillus sibiricus, and the genera Russula, Pseudotomentella were identified. Molecularly the ECM fungi T. terrestris, Inocybe jacobi and the genera Sphaerosporella and several other ECM containing families were identified along with many saprotrophic/endophytic fungi belonging to genera such as, Penicillium, Ramasonia and Talaromyces. Inoculated seedlings showed a significant increase in growth in comparison to the un-inoculated control seedlings. ECM fungal colonisation levels of these seedlings were significantly increased and colonisation was promoted by the Suillus isolate, Salmon Suillus. Seedling growth in the presence of the pathogen F. circinatum was significantly increased and promoted by the Lactarius isolate Lactarius quieticolor. Inoculation of seedlings in the nursery would ensure the production of stronger healthy plants which may be more tolerant to fusarial infection increasing survival in the plantation. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2019
- Full Text:
- Date Issued: 2019
- Authors: FitzGerald, Véronique Chartier
- Date: 2019
- Subjects: Ectomycorrhizal fungi , Pinus patula Diseases and pests Biological control South Africa , Fusarium , Forest nurseries , Seedlings Growth , Seedlings Diseases and pests
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/67902 , vital:29167
- Description: The South Africa forestry industry, covering 1.3 million hectares, is dependent on exotic pine and eucalyptus species. Nursery seedlings are not inoculated with ectomycorrhizal (ECM) fungi or other beneficial microbes. Fusarium circinatum is an economically important pathogen affecting seedling survival. The purpose of this investigation was to assess levels of naturally occurring ECM colonisation in South African nurseries and to determine the effects of seedling inoculation with selected ECM and bacterial isolates on plant growth and resistance to the fungal pathogen F. circiantum. Pinus patula seedlings from 10 different South African nurseries were assessed for ECM colonisation using a grid line intersect method and molecularly identified using morphological and next-generation Illumina sequencing. Explants from ECM basidiocarps, collected from Pinus stands, were plated onto MMN medium to obtain isolates which were verified using molecular techniques. Mycorrhizal helper bacteria (MHB) were also isolated from these basiocarps, tested for MHB properties, siderophore production, phospahte solubilising and IAA production. ECM and associated bacterial isolates were used to inoculate seedlings and growth was assessed over a 5 month period. Colonisation of seedlings in production nurseries was low (2-21%). Morphologically the ECM fungi T. terrestris, Suillus sibiricus, and the genera Russula, Pseudotomentella were identified. Molecularly the ECM fungi T. terrestris, Inocybe jacobi and the genera Sphaerosporella and several other ECM containing families were identified along with many saprotrophic/endophytic fungi belonging to genera such as, Penicillium, Ramasonia and Talaromyces. Inoculated seedlings showed a significant increase in growth in comparison to the un-inoculated control seedlings. ECM fungal colonisation levels of these seedlings were significantly increased and colonisation was promoted by the Suillus isolate, Salmon Suillus. Seedling growth in the presence of the pathogen F. circinatum was significantly increased and promoted by the Lactarius isolate Lactarius quieticolor. Inoculation of seedlings in the nursery would ensure the production of stronger healthy plants which may be more tolerant to fusarial infection increasing survival in the plantation. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2019
- Full Text:
- Date Issued: 2019
Rhodeo, Vol. 22, No. 16
- Date: 1968-08-22
- Subjects: Grahamstown -- Newspapers , Journalism, Students -- South Africa , Rhodes University -- Activate , Rhodes University -- Students , Student newspapers and periodicals -- South Africa
- Language: English
- Type: Text
- Identifier: vital:14590 , http://hdl.handle.net/10962/d1019462
- Description: Rhodeo is the Independent Student Newspaper of Rhodes University. Located in Grahamstown, Rhodeo was established in 1947, and renamed in 1994 as Activate. During apartheid Rhodeo became an active part of the struggle for freedom of expression as part of the now defunct South African Student Press Union. Currently Activate is committed to informing Rhodes University students, staff and community members about relevant issues, mainly on campus. These issues range from hard news to more creative journalism. While Activate acts as a news source, one of its main objectives it to be accessible as a training ground for student journalists. The newspaper is run entirely by the students and is published twice a term. Activate is a free newspaper which receives an annual grant from the Rhodes University Student Representative Council, however, majority of its revenue is generated through advertising.
- Full Text:
- Date Issued: 1968-08-22
- Date: 1968-08-22
- Subjects: Grahamstown -- Newspapers , Journalism, Students -- South Africa , Rhodes University -- Activate , Rhodes University -- Students , Student newspapers and periodicals -- South Africa
- Language: English
- Type: Text
- Identifier: vital:14590 , http://hdl.handle.net/10962/d1019462
- Description: Rhodeo is the Independent Student Newspaper of Rhodes University. Located in Grahamstown, Rhodeo was established in 1947, and renamed in 1994 as Activate. During apartheid Rhodeo became an active part of the struggle for freedom of expression as part of the now defunct South African Student Press Union. Currently Activate is committed to informing Rhodes University students, staff and community members about relevant issues, mainly on campus. These issues range from hard news to more creative journalism. While Activate acts as a news source, one of its main objectives it to be accessible as a training ground for student journalists. The newspaper is run entirely by the students and is published twice a term. Activate is a free newspaper which receives an annual grant from the Rhodes University Student Representative Council, however, majority of its revenue is generated through advertising.
- Full Text:
- Date Issued: 1968-08-22
Study of the biotransformations and microbiological properties of cymbopogon citratus
- Ajayi, Emmanuel Olusegun https://orcid.org/0000-0002-0838-4948
- Authors: Ajayi, Emmanuel Olusegun https://orcid.org/0000-0002-0838-4948
- Date: 2015
- Subjects: Lemongras , Essences and essential oils
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/19737 , vital:43197
- Description: Variations in the essential oil yield, chemical composition and kinetics of chemical transformation, antibacterial, and antioxidant properties of the Cymbopogon citratus cultivated in Alice, Eastern Cape of South Africa, over a period of 12 months using the solvent-free microwave extraction and the modified forms of conventional hydrodistillation methods have been evaluated. The modified forms involve variation in the pH medium to effect extraction and to obtain the whole leaf extracts of Cymbopogon citratus (lemongrass). The GC-MS analyses of the essential oils revealed the presence of 10, 11, 13, and 9 principal compounds in the microwave, extraction, hydrodistillation (water-distilled), hydrodistillation (aciddistilled and hydrodistillation (base-distilled), respectively with citral being the prominent compound in all the various extraction methods, with the water-distilled method having the highest cumulative citral content under the period specified. Each of the components of the oils varied in quantity and quality of yield at different points of the year. Different extraction methods produce different compounds. Increase in the amount of citral content was observed during the maturation stage of Cymbopogon citratus in all the extraction methods. Quantitative evaluation of antibacterial activity, minimum inhibitory concentration (MIC) values were determined on the oils and extracts of Cymbopogon citratus using agar dilution method. The essential oils obtained using all the methods of extraction showed activity against all the tested bacteria at a concentration of 10 mg mL-1. The minimum inhibitory concentrations for the acid-distilled varied between 1.25 and 5.0 mg mL-1, while those obtained by both water- and base-distilled showed equal activity on the microorganisms with the MIC ranging between 2.5 and 10 mg mL-1. The microwave extraction showed the least activity with the MIC of 10 mg mL-1. This however suggested that the oils obtained through acid-distillation showed the greatest activity than all other methods of extraction. Activity of the various extracts on bacteria showed that the ethanol extract had the highest activity on the tested organisms with MIC ranging between 0.625 and 1.25 mg mL-1. This was closely followed by the acid-extract (1.25 and 5.0 mg mL-1), methanol extract (1.25 and 10 mg mL-1), acetone extract (2.5 and 5.0 mg mL-1), and base extract (5.0 mg mL-1). Both cold water and hot water extracts showed the least activity of MIC, >10 mg mL-1. The antioxidant and free-radical scavenging activity of the obtained oils and extracts were tested by means of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH+) assay, [(2,2ˊ-azino bis-(3-ethylbenzothiazoline-6-sulfonic acid)] (ABTS), nitric oxide and ferric reducing power assays. The oils and extracts showed DPPH radical scavenging ability, but not as high as the standard drugs. The base extract showed a higher reducing power than the standard drug, rutin. There were significant differences in the phytochemicals contents of the various leaf extracts. The acetone extract has the highest flavonol, proanthocyanidin, and alkaloid contents. The ethanol extract showed the highest amount of phenolic content with the acid extract, having the least. Thin layer chromatography (TLC) and column chromatography was employed to obtain different fractions of extracts using four eluent solvent systems of varying polarities: toluene, petroleum ether, hexane and ethyl acetate and sprayed with anisaldehyde. A single, visible spot of B-fraction was developed, collected and analyzed as 1-methyl-2,4,5- trinitroimidazole with renown valuable properties. , Thesis (PhD) -- Faculty of Science and Agriculture, 2015
- Full Text:
- Date Issued: 2015
- Authors: Ajayi, Emmanuel Olusegun https://orcid.org/0000-0002-0838-4948
- Date: 2015
- Subjects: Lemongras , Essences and essential oils
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/19737 , vital:43197
- Description: Variations in the essential oil yield, chemical composition and kinetics of chemical transformation, antibacterial, and antioxidant properties of the Cymbopogon citratus cultivated in Alice, Eastern Cape of South Africa, over a period of 12 months using the solvent-free microwave extraction and the modified forms of conventional hydrodistillation methods have been evaluated. The modified forms involve variation in the pH medium to effect extraction and to obtain the whole leaf extracts of Cymbopogon citratus (lemongrass). The GC-MS analyses of the essential oils revealed the presence of 10, 11, 13, and 9 principal compounds in the microwave, extraction, hydrodistillation (water-distilled), hydrodistillation (aciddistilled and hydrodistillation (base-distilled), respectively with citral being the prominent compound in all the various extraction methods, with the water-distilled method having the highest cumulative citral content under the period specified. Each of the components of the oils varied in quantity and quality of yield at different points of the year. Different extraction methods produce different compounds. Increase in the amount of citral content was observed during the maturation stage of Cymbopogon citratus in all the extraction methods. Quantitative evaluation of antibacterial activity, minimum inhibitory concentration (MIC) values were determined on the oils and extracts of Cymbopogon citratus using agar dilution method. The essential oils obtained using all the methods of extraction showed activity against all the tested bacteria at a concentration of 10 mg mL-1. The minimum inhibitory concentrations for the acid-distilled varied between 1.25 and 5.0 mg mL-1, while those obtained by both water- and base-distilled showed equal activity on the microorganisms with the MIC ranging between 2.5 and 10 mg mL-1. The microwave extraction showed the least activity with the MIC of 10 mg mL-1. This however suggested that the oils obtained through acid-distillation showed the greatest activity than all other methods of extraction. Activity of the various extracts on bacteria showed that the ethanol extract had the highest activity on the tested organisms with MIC ranging between 0.625 and 1.25 mg mL-1. This was closely followed by the acid-extract (1.25 and 5.0 mg mL-1), methanol extract (1.25 and 10 mg mL-1), acetone extract (2.5 and 5.0 mg mL-1), and base extract (5.0 mg mL-1). Both cold water and hot water extracts showed the least activity of MIC, >10 mg mL-1. The antioxidant and free-radical scavenging activity of the obtained oils and extracts were tested by means of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH+) assay, [(2,2ˊ-azino bis-(3-ethylbenzothiazoline-6-sulfonic acid)] (ABTS), nitric oxide and ferric reducing power assays. The oils and extracts showed DPPH radical scavenging ability, but not as high as the standard drugs. The base extract showed a higher reducing power than the standard drug, rutin. There were significant differences in the phytochemicals contents of the various leaf extracts. The acetone extract has the highest flavonol, proanthocyanidin, and alkaloid contents. The ethanol extract showed the highest amount of phenolic content with the acid extract, having the least. Thin layer chromatography (TLC) and column chromatography was employed to obtain different fractions of extracts using four eluent solvent systems of varying polarities: toluene, petroleum ether, hexane and ethyl acetate and sprayed with anisaldehyde. A single, visible spot of B-fraction was developed, collected and analyzed as 1-methyl-2,4,5- trinitroimidazole with renown valuable properties. , Thesis (PhD) -- Faculty of Science and Agriculture, 2015
- Full Text:
- Date Issued: 2015
Chemical transformations and phytochemical studies of bioactive components from extracts of Rosmarinus officinalis L
- Authors: Okoh, Omobola Oluranti
- Date: 2010
- Subjects: Essences and essential oils , Rosmarinus , Lamiaceae , Solution (Chemistry) , Extractive distillation , Medicinal plants , Bioactive compounds
- Language: English
- Type: Thesis , Doctoral , PhD (Chemistry)
- Identifier: vital:11331 , http://hdl.handle.net/10353/354 , Essences and essential oils , Rosmarinus , Lamiaceae , Solution (Chemistry) , Extractive distillation , Medicinal plants , Bioactive compounds
- Description: Variations in the yield, chemical composition, antibacterial, and antioxidant properties of the essential oils of Rosmarinus officinalis L. cultivated in Alice, Eastern Cape of South Africa over a period of 12 months using the solvent-free microwave extraction and traditional hydrodistillation methods were evaluated. The GC-MS analyses of the essential oils revealed the presence of 33 compounds with 1,8-cineole, a-pinene, camphor, verbenone, bornyl acetate and camphene constituting about 80 percent of the oils throughout the period of investigation, with the solvent-free microwave extraction method generally yielding more of the major components than the hydrodistillation method. Each of the major components of the oils varied in quantity and quality of yield at different periods of the year. The method of extraction and time of harvest are of importance to the quantity and quality of essential oil of Rosmarinus officinalis. Higher amounts of oxygenated monoterpenes such as borneol, camphor, terpene- 4-ol, linalool, a-terpeneol were present in the oil of SFME in comparison with HD. However, HD oil contained more monoterpene hydrocarbons such as a-pinene, camphene, β-pinene, myrcene, a-phellanderene, 1,8-cineole, trans- β-ocimene, γ-teprinene, and cis-sabinene hydrate than SFME extracted oil. Accumulation of monoterpene alcohols and ketones was observed during maturation process of Rosmarinus leaves. Quantitative evaluation of antibacterial activity, minimum inhibitory concentration values were determined using a serial microplate dilution method. The essential oils obtained using both methods of extraction were active against all the bacteria tested at a concentration of 10 mg mL-1. The minimum inhibitory concentrations for the SFME extracted oils ranged between 0.23 and 1.88 mg mL-1, while those of the HD extracted oils varied between 0.94 and 7.5 mg mL-1, thus suggesting that the oil obtained by solvent free microwave extraction was more active against bacteria than the oil obtained through hydrodistillation. The antioxidant and free radical scavenging activity of the obtained oils were tested by means of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH+) assay and β- carotene bleaching test. In the DPPH+ assay, while the free radical scavenging activity of the oil obtained by SFME method showed percentage inhibitions of between 48.8 percent and 67 percent, the HD derived oil showed inhibitions of between 52.2 percent and 65.30 percent at concentrations of 0.33, 0.50 and 1.0 mg mL-1, respectively. In the β-carotene bleaching assay, the percentage inhibition increased with increasing concentration of both oils with a higher antioxidant activity of the oil obtained through the SFME than the HD method. Thin layer chromatography (TLC) was used to analyze the chemical composition of the extracts using three eluent solvent systems of varying polarities i. e. CEF, BEA and EMW and sprayed with vanillin-sulfuric acid. The chemical composition of the different extracts was similar with the exception of methanol and water extracts which had only one or two visible compounds after treating with vanillin-spray reagent. To evaluate the number of antibacterial compounds present in the fractions, bioautography was used against two most important nosocomial microorganisms. S. aureus (Gram positive) and E. coli (Gram negative). Nearly all the crude serial extraction fractions contained compounds that inhibited the growth of E. coli. The hexane extract had the most lines of inhibition followed by ethyl acetate. Bioassay-guided fractionation against E. coli was used to isolate antibacterial compounds. The largest number of antibacterial compounds occurred in the hexane fraction. Furthermore we tried to complete the characterization by extracting and studying other biologically important plant metabolites such as phenolic compounds to evaluate the antioxidant capacity of Rosmarinus extracts.
- Full Text:
- Date Issued: 2010
- Authors: Okoh, Omobola Oluranti
- Date: 2010
- Subjects: Essences and essential oils , Rosmarinus , Lamiaceae , Solution (Chemistry) , Extractive distillation , Medicinal plants , Bioactive compounds
- Language: English
- Type: Thesis , Doctoral , PhD (Chemistry)
- Identifier: vital:11331 , http://hdl.handle.net/10353/354 , Essences and essential oils , Rosmarinus , Lamiaceae , Solution (Chemistry) , Extractive distillation , Medicinal plants , Bioactive compounds
- Description: Variations in the yield, chemical composition, antibacterial, and antioxidant properties of the essential oils of Rosmarinus officinalis L. cultivated in Alice, Eastern Cape of South Africa over a period of 12 months using the solvent-free microwave extraction and traditional hydrodistillation methods were evaluated. The GC-MS analyses of the essential oils revealed the presence of 33 compounds with 1,8-cineole, a-pinene, camphor, verbenone, bornyl acetate and camphene constituting about 80 percent of the oils throughout the period of investigation, with the solvent-free microwave extraction method generally yielding more of the major components than the hydrodistillation method. Each of the major components of the oils varied in quantity and quality of yield at different periods of the year. The method of extraction and time of harvest are of importance to the quantity and quality of essential oil of Rosmarinus officinalis. Higher amounts of oxygenated monoterpenes such as borneol, camphor, terpene- 4-ol, linalool, a-terpeneol were present in the oil of SFME in comparison with HD. However, HD oil contained more monoterpene hydrocarbons such as a-pinene, camphene, β-pinene, myrcene, a-phellanderene, 1,8-cineole, trans- β-ocimene, γ-teprinene, and cis-sabinene hydrate than SFME extracted oil. Accumulation of monoterpene alcohols and ketones was observed during maturation process of Rosmarinus leaves. Quantitative evaluation of antibacterial activity, minimum inhibitory concentration values were determined using a serial microplate dilution method. The essential oils obtained using both methods of extraction were active against all the bacteria tested at a concentration of 10 mg mL-1. The minimum inhibitory concentrations for the SFME extracted oils ranged between 0.23 and 1.88 mg mL-1, while those of the HD extracted oils varied between 0.94 and 7.5 mg mL-1, thus suggesting that the oil obtained by solvent free microwave extraction was more active against bacteria than the oil obtained through hydrodistillation. The antioxidant and free radical scavenging activity of the obtained oils were tested by means of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH+) assay and β- carotene bleaching test. In the DPPH+ assay, while the free radical scavenging activity of the oil obtained by SFME method showed percentage inhibitions of between 48.8 percent and 67 percent, the HD derived oil showed inhibitions of between 52.2 percent and 65.30 percent at concentrations of 0.33, 0.50 and 1.0 mg mL-1, respectively. In the β-carotene bleaching assay, the percentage inhibition increased with increasing concentration of both oils with a higher antioxidant activity of the oil obtained through the SFME than the HD method. Thin layer chromatography (TLC) was used to analyze the chemical composition of the extracts using three eluent solvent systems of varying polarities i. e. CEF, BEA and EMW and sprayed with vanillin-sulfuric acid. The chemical composition of the different extracts was similar with the exception of methanol and water extracts which had only one or two visible compounds after treating with vanillin-spray reagent. To evaluate the number of antibacterial compounds present in the fractions, bioautography was used against two most important nosocomial microorganisms. S. aureus (Gram positive) and E. coli (Gram negative). Nearly all the crude serial extraction fractions contained compounds that inhibited the growth of E. coli. The hexane extract had the most lines of inhibition followed by ethyl acetate. Bioassay-guided fractionation against E. coli was used to isolate antibacterial compounds. The largest number of antibacterial compounds occurred in the hexane fraction. Furthermore we tried to complete the characterization by extracting and studying other biologically important plant metabolites such as phenolic compounds to evaluate the antioxidant capacity of Rosmarinus extracts.
- Full Text:
- Date Issued: 2010
Variation in the essential oil composition of Calendula Officinalis L
- Authors: Okoh, Omobola Oluranti
- Date: 2008
- Subjects: Calendula (Genus) , Essences and essential oils , Medicinal plants , Calendula officinalis
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11334 , http://hdl.handle.net/10353/d1001150 , Calendula (Genus) , Essences and essential oils , Medicinal plants , Calendula officinalis
- Description: Variations in the yield, chemical composition, antibacterial, and antioxidant properties of the essential oils of Rosmarinus officinalis L. cultivated in Alice, Eastern Cape of South Africa over a period of 12 months using the solvent-free microwave extraction and traditional hydrodistillation methods were evaluated. The GC-MS analyses of the essential oils revealed the presence of 33 compounds with 1,8-cineole, a-pinene, camphor, verbenone, bornyl acetate and camphene constituting about 80 percent of the oils throughout the period of investigation, with the solvent-free microwave extraction method generally yielding more of the major components than the hydrodistillation method. Each of the major components of the oils varied in quantity and quality of yield at different periods of the year. The method of extraction and time of harvest are of importance to the quantity and quality of essential oil of Rosmarinus officinalis. Higher amounts of oxygenated monoterpenes such as borneol, camphor, terpene- 4-ol, linalool, a-terpeneol were present in the oil of SFME in comparison with HD. However, HD oil contained more monoterpene hydrocarbons such as a-pinene, camphene, β-pinene, myrcene, a-phellanderene, 1,8-cineole, trans- β-ocimene, γ-teprinene, and cis-sabinene hydrate than SFME extracted oil. Accumulation of monoterpene alcohols and ketones was observed during maturation process of Rosmarinus leaves. Quantitative evaluation of antibacterial activity, minimum inhibitory concentration values were determined using a serial microplate dilution method. The essential oils obtained using both methods of extraction were active against all the bacteria tested at a concentration of 10 mg mL-1. The minimum inhibitory concentrations for the SFME extracted oils ranged between 0.23 and 1.88 mg mL-1, while those of the HD extracted oils varied between 0.94 and 7.5 mg mL-1, thus suggesting that the oil obtained by solvent free microwave extraction was more active against bacteria than the oil obtained through hydrodistillation. The antioxidant and free radical scavenging activity of the obtained oils were tested by means of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH+) assay and β- carotene bleaching test. In the DPPH+ assay, while the free radical scavenging activity of the oil obtained by SFME method showed percentage inhibitions of between 48.8 percent and 67 percent, the HD derived oil showed inhibitions of between 52.2 percent and 65.30 percent at concentrations of 0.33, 0.50 and 1.0 mg mL-1, respectively. In the β-carotene bleaching assay, the percentage inhibition increased with increasing concentration of both oils with a higher antioxidant activity of the oil obtained through the SFME than the HD method. Thin layer chromatography (TLC) was used to analyze the chemical composition of the extracts using three eluent solvent systems of varying polarities i. e. CEF, BEA and EMW and sprayed with vanillin-sulfuric acid. The chemical composition of the different extracts was similar with the exception of methanol and water extracts which had only one or two visible compounds after treating with vanillin-spray reagent. To evaluate the number of antibacterial compounds present in the fractions, bioautography was used against two most important nosocomial microorganisms. S. aureus (Gram positive) and E. coli (Gram negative). Nearly all the crude serial extraction fractions contained compounds that inhibited the growth of E. coli. The hexane extract had the most lines of inhibition followed by ethyl acetate. Bioassay-guided fractionation against E. coli was used to isolate antibacterial compounds. The largest number of antibacterial compounds occurred in the hexane fraction. Furthermore we tried to complete the characterization by extracting and studying other biologically important plant metabolites such as phenolic compounds to evaluate the antioxidant capacity of Rosmarinus extracts
- Full Text:
- Date Issued: 2008
- Authors: Okoh, Omobola Oluranti
- Date: 2008
- Subjects: Calendula (Genus) , Essences and essential oils , Medicinal plants , Calendula officinalis
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11334 , http://hdl.handle.net/10353/d1001150 , Calendula (Genus) , Essences and essential oils , Medicinal plants , Calendula officinalis
- Description: Variations in the yield, chemical composition, antibacterial, and antioxidant properties of the essential oils of Rosmarinus officinalis L. cultivated in Alice, Eastern Cape of South Africa over a period of 12 months using the solvent-free microwave extraction and traditional hydrodistillation methods were evaluated. The GC-MS analyses of the essential oils revealed the presence of 33 compounds with 1,8-cineole, a-pinene, camphor, verbenone, bornyl acetate and camphene constituting about 80 percent of the oils throughout the period of investigation, with the solvent-free microwave extraction method generally yielding more of the major components than the hydrodistillation method. Each of the major components of the oils varied in quantity and quality of yield at different periods of the year. The method of extraction and time of harvest are of importance to the quantity and quality of essential oil of Rosmarinus officinalis. Higher amounts of oxygenated monoterpenes such as borneol, camphor, terpene- 4-ol, linalool, a-terpeneol were present in the oil of SFME in comparison with HD. However, HD oil contained more monoterpene hydrocarbons such as a-pinene, camphene, β-pinene, myrcene, a-phellanderene, 1,8-cineole, trans- β-ocimene, γ-teprinene, and cis-sabinene hydrate than SFME extracted oil. Accumulation of monoterpene alcohols and ketones was observed during maturation process of Rosmarinus leaves. Quantitative evaluation of antibacterial activity, minimum inhibitory concentration values were determined using a serial microplate dilution method. The essential oils obtained using both methods of extraction were active against all the bacteria tested at a concentration of 10 mg mL-1. The minimum inhibitory concentrations for the SFME extracted oils ranged between 0.23 and 1.88 mg mL-1, while those of the HD extracted oils varied between 0.94 and 7.5 mg mL-1, thus suggesting that the oil obtained by solvent free microwave extraction was more active against bacteria than the oil obtained through hydrodistillation. The antioxidant and free radical scavenging activity of the obtained oils were tested by means of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH+) assay and β- carotene bleaching test. In the DPPH+ assay, while the free radical scavenging activity of the oil obtained by SFME method showed percentage inhibitions of between 48.8 percent and 67 percent, the HD derived oil showed inhibitions of between 52.2 percent and 65.30 percent at concentrations of 0.33, 0.50 and 1.0 mg mL-1, respectively. In the β-carotene bleaching assay, the percentage inhibition increased with increasing concentration of both oils with a higher antioxidant activity of the oil obtained through the SFME than the HD method. Thin layer chromatography (TLC) was used to analyze the chemical composition of the extracts using three eluent solvent systems of varying polarities i. e. CEF, BEA and EMW and sprayed with vanillin-sulfuric acid. The chemical composition of the different extracts was similar with the exception of methanol and water extracts which had only one or two visible compounds after treating with vanillin-spray reagent. To evaluate the number of antibacterial compounds present in the fractions, bioautography was used against two most important nosocomial microorganisms. S. aureus (Gram positive) and E. coli (Gram negative). Nearly all the crude serial extraction fractions contained compounds that inhibited the growth of E. coli. The hexane extract had the most lines of inhibition followed by ethyl acetate. Bioassay-guided fractionation against E. coli was used to isolate antibacterial compounds. The largest number of antibacterial compounds occurred in the hexane fraction. Furthermore we tried to complete the characterization by extracting and studying other biologically important plant metabolites such as phenolic compounds to evaluate the antioxidant capacity of Rosmarinus extracts
- Full Text:
- Date Issued: 2008
Mediating and examining expansive learning in the context of multidimensional complexities affecting household food security activity systems in Nyanyadzi Irrigation Scheme in the Manicaland Province of Zimbabwe
- Authors: Mukwambo, Robson
- Date: 2021-10-29
- Subjects: Active learning Zimbabwe Chimanimani District , Food security Zimbabwe Chimanimani District , Sustainable agriculture Zimbabwe Chimanimani District , Irrigation farming Zimbabwe Chimanimani District , Qualitative research , Cultural-historical activity theory (CHAT) , Nyanyadzi Irrigation Scheme
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192712 , vital:45253 , 10.21504/10962/192712
- Description: The study sought to mediate and examine expansive learning in the context of multidimensional complexities affecting household food security activity systems in Nyanyadzi Irrigation Scheme in Ward 8 of Chimanimani District in the Manicaland province of Zimbabwe. Therefore, the main foci of the study were to investigate how multidimensional complexities have come to be the way they are (historicizing) and how they enable or constrain learning of household food production. The study utilized Cultural Historical Activity Theory and the Expansive Learning Cycle (Engeström & Sannino, 2010) to examine and mediate collective learning in response to the multidimensional complexities and also to contribute to transforming the farmers’ activity systems towards more sustainable practices to ensure household food security. The study used a qualitative research approach, utilizing an insider formative intervention approach in a case study design in which Nyanyadzi irrigation scheme was the case study. I have adopted the insider formative interventionist role as a 3rd generation farmer, born and bred in Nyanyadzi area, and my family has been involved in the Nyanyadzi irrigation scheme for three generations. I see this as synergistic with the need for deep cultural understanding in CHAT research. However, this role also provided challenges for me to maintain a rigorous approach to the research in which I also reflexively review my own role and influence in the research process. Following CHAT expansive learning methodological guidance, data was generated through fifteen (15) face to face interviews with three generations of farmers in the scheme (historical ethnographic data); four focus group discussions (contemporary ethnographic data) and eight (8) sessions in a three (3) day change laboratory workshop (expansive learning data). Double stimulation and ‘mirror’ data was used to surface and prioritise responses to contradictions in the Change Laboratory Workshops (CLW), which is a methodology developed in and for CHAT research (ibid). The data was analysed using both inductive and abductive approaches and were conducted in a three-phased process focusing firstly on the history of the object, followed by current perspectives on the object of activity and lastly on transformations emerging in the object of activity via the expansive learning process. Cultural Historical Activity Theoretical tools informed activity system analysis and analysis of the history of the object and emerging contradictions; and the expansive learning cycle (ELP) process framework associated with and emergent from CHAT was used to analyse the emergence of transformative agency and expansion of the object. Four levels of contradictions were used to describe and explain the emergent contradictions namely, primary, secondary, tertiary and quaternary contradictions and are presented in this sequence as catalytic opportunities for expansive learning as proposed in CHAT. In addition, the four types of discursive manifestations of contradictions namely, dilemma, conflict, critical conflict and double bind were used to describe and explain the manifestations of contradictions in this study and their role in catalysing transformative agency. The concept of linguistic cues for discursive manifestations of contradictions was adopted and employed in the preliminary data analysis phase. In addition, the transformative agency expressions and zone of proximal development (ZPD) concept was applied in and to the CLW data to examine the learning pathways and to co-develop and expand farmers’ and other stakeholders’ transformative agency and ZPD respectively. I found myself as formative insider researcher having to take on a strong role as co-engaged researcher / participant in the irrigation scheme expansive learning process. The study concluded that the farmers’ activity system is the central activity system and it interacts with other activity systems on a partially shared object “improved crop production and marketing under irrigation scheme”. Through interactions with other neighbouring activity systems, the farmers have faced multidimensional complexities that constrain their ability to fully realise their object. These multidimensional complexities manifest in three critical contradictions as a critical conflict in leadership and management crisis; a dilemma and double bind in a lack of farmer education and training; and lastly, a dilemma and double bind in poor crop marketing. These multidimensional complexities have a historical account and they have evolved in complexity over time and I argue in the thesis that, a careful cultural-historicity of the object of activity and mediation of the situated learning can help to collectively come up with solutions to these multidimensional complexities. The study further concluded that despite these multidimensional complexities in the scheme, learning has been taking place and such learning was sometimes mediated through demonstrations as “learning by doing,” “seeing is believing” and the “winners and losers” concept. Furthermore, through the CLW process the farmers and other stakeholders’ cognitive horizons were expanded by the mirror data and double stimulation processes, and the expansive learning process developed their individual and collective transformative agency pathways and expanded their collective zone of proximal development. In this study I argue that there has been little said about collective learning in irrigation schemes and given the dearth of detail on such learning, it seems that this learning is either going unnoticed or is ignored. Hence, I further argued that the multidimensional complexities in irrigation schemes are both a stimulant for learning and provide a space (object) for collective learning, as was also shown by Baloi (2016). The study also shows that the collective learning potential in these irrigation schemes can be pro-actively mediated via expansive learning formative interventions in support of improved crop production and marketing for produce developed under irrigation in irrigation schemes such as the Nyanyadzi Irrigation scheme. Lastly, being an insider formative interventionist researcher in this study, with intergenerational engagement and perspective on the history of the object and integrational engagement with the transforming object, I became part of the intergenerational transformation of the irrigation scheme’s object. The intergenerational co-construction of the history of the object, coupled with the insider formative interventionist researcher approach opened up and allowed me as a current generation agent or actor to develop an in-depth understanding of the multidimensional nature and historicity of the object. This was crucial for opening up the transformative agency pathways. It also produced a responsibility for me as an insider formative interventionist researcher to carry the summative findings of the study back into the social context to widen the engagement and mediation of the transformation needed in the community. Overall not only does the study offer an intergenerational perspective on multidimensional complexities of the object and how this can generatively be mobilised via expansive learning into emerging transformative learning agency pathways, but it also offers a new vantage point on the role of the insider formative interventionist researcher. Through this, the study offers insight into how we as third generation members of the community can be brought closer to our communities through the application of our skills, thereby also offering a new type of engaged and rigorously framed and executed research with roots in our communities. As shown in this study, not only does this expand the knowledge and experience of those we engage with, but it also expands our own knowledge and expertise in order to be more able to contribute to both the challenges of our own communities but also that of other communities and situations similar to ours, and beyond these bounded contexts. The study’s contribution is both practical, but also methodological from this vantage point, especially in an African context where there is much critique of ‘outsider research’, yet little pro-active articulation of what insider (in this case, formative intervention) research may look like. , Thesis (PhD) -- Faculty of Education, Education, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Mukwambo, Robson
- Date: 2021-10-29
- Subjects: Active learning Zimbabwe Chimanimani District , Food security Zimbabwe Chimanimani District , Sustainable agriculture Zimbabwe Chimanimani District , Irrigation farming Zimbabwe Chimanimani District , Qualitative research , Cultural-historical activity theory (CHAT) , Nyanyadzi Irrigation Scheme
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192712 , vital:45253 , 10.21504/10962/192712
- Description: The study sought to mediate and examine expansive learning in the context of multidimensional complexities affecting household food security activity systems in Nyanyadzi Irrigation Scheme in Ward 8 of Chimanimani District in the Manicaland province of Zimbabwe. Therefore, the main foci of the study were to investigate how multidimensional complexities have come to be the way they are (historicizing) and how they enable or constrain learning of household food production. The study utilized Cultural Historical Activity Theory and the Expansive Learning Cycle (Engeström & Sannino, 2010) to examine and mediate collective learning in response to the multidimensional complexities and also to contribute to transforming the farmers’ activity systems towards more sustainable practices to ensure household food security. The study used a qualitative research approach, utilizing an insider formative intervention approach in a case study design in which Nyanyadzi irrigation scheme was the case study. I have adopted the insider formative interventionist role as a 3rd generation farmer, born and bred in Nyanyadzi area, and my family has been involved in the Nyanyadzi irrigation scheme for three generations. I see this as synergistic with the need for deep cultural understanding in CHAT research. However, this role also provided challenges for me to maintain a rigorous approach to the research in which I also reflexively review my own role and influence in the research process. Following CHAT expansive learning methodological guidance, data was generated through fifteen (15) face to face interviews with three generations of farmers in the scheme (historical ethnographic data); four focus group discussions (contemporary ethnographic data) and eight (8) sessions in a three (3) day change laboratory workshop (expansive learning data). Double stimulation and ‘mirror’ data was used to surface and prioritise responses to contradictions in the Change Laboratory Workshops (CLW), which is a methodology developed in and for CHAT research (ibid). The data was analysed using both inductive and abductive approaches and were conducted in a three-phased process focusing firstly on the history of the object, followed by current perspectives on the object of activity and lastly on transformations emerging in the object of activity via the expansive learning process. Cultural Historical Activity Theoretical tools informed activity system analysis and analysis of the history of the object and emerging contradictions; and the expansive learning cycle (ELP) process framework associated with and emergent from CHAT was used to analyse the emergence of transformative agency and expansion of the object. Four levels of contradictions were used to describe and explain the emergent contradictions namely, primary, secondary, tertiary and quaternary contradictions and are presented in this sequence as catalytic opportunities for expansive learning as proposed in CHAT. In addition, the four types of discursive manifestations of contradictions namely, dilemma, conflict, critical conflict and double bind were used to describe and explain the manifestations of contradictions in this study and their role in catalysing transformative agency. The concept of linguistic cues for discursive manifestations of contradictions was adopted and employed in the preliminary data analysis phase. In addition, the transformative agency expressions and zone of proximal development (ZPD) concept was applied in and to the CLW data to examine the learning pathways and to co-develop and expand farmers’ and other stakeholders’ transformative agency and ZPD respectively. I found myself as formative insider researcher having to take on a strong role as co-engaged researcher / participant in the irrigation scheme expansive learning process. The study concluded that the farmers’ activity system is the central activity system and it interacts with other activity systems on a partially shared object “improved crop production and marketing under irrigation scheme”. Through interactions with other neighbouring activity systems, the farmers have faced multidimensional complexities that constrain their ability to fully realise their object. These multidimensional complexities manifest in three critical contradictions as a critical conflict in leadership and management crisis; a dilemma and double bind in a lack of farmer education and training; and lastly, a dilemma and double bind in poor crop marketing. These multidimensional complexities have a historical account and they have evolved in complexity over time and I argue in the thesis that, a careful cultural-historicity of the object of activity and mediation of the situated learning can help to collectively come up with solutions to these multidimensional complexities. The study further concluded that despite these multidimensional complexities in the scheme, learning has been taking place and such learning was sometimes mediated through demonstrations as “learning by doing,” “seeing is believing” and the “winners and losers” concept. Furthermore, through the CLW process the farmers and other stakeholders’ cognitive horizons were expanded by the mirror data and double stimulation processes, and the expansive learning process developed their individual and collective transformative agency pathways and expanded their collective zone of proximal development. In this study I argue that there has been little said about collective learning in irrigation schemes and given the dearth of detail on such learning, it seems that this learning is either going unnoticed or is ignored. Hence, I further argued that the multidimensional complexities in irrigation schemes are both a stimulant for learning and provide a space (object) for collective learning, as was also shown by Baloi (2016). The study also shows that the collective learning potential in these irrigation schemes can be pro-actively mediated via expansive learning formative interventions in support of improved crop production and marketing for produce developed under irrigation in irrigation schemes such as the Nyanyadzi Irrigation scheme. Lastly, being an insider formative interventionist researcher in this study, with intergenerational engagement and perspective on the history of the object and integrational engagement with the transforming object, I became part of the intergenerational transformation of the irrigation scheme’s object. The intergenerational co-construction of the history of the object, coupled with the insider formative interventionist researcher approach opened up and allowed me as a current generation agent or actor to develop an in-depth understanding of the multidimensional nature and historicity of the object. This was crucial for opening up the transformative agency pathways. It also produced a responsibility for me as an insider formative interventionist researcher to carry the summative findings of the study back into the social context to widen the engagement and mediation of the transformation needed in the community. Overall not only does the study offer an intergenerational perspective on multidimensional complexities of the object and how this can generatively be mobilised via expansive learning into emerging transformative learning agency pathways, but it also offers a new vantage point on the role of the insider formative interventionist researcher. Through this, the study offers insight into how we as third generation members of the community can be brought closer to our communities through the application of our skills, thereby also offering a new type of engaged and rigorously framed and executed research with roots in our communities. As shown in this study, not only does this expand the knowledge and experience of those we engage with, but it also expands our own knowledge and expertise in order to be more able to contribute to both the challenges of our own communities but also that of other communities and situations similar to ours, and beyond these bounded contexts. The study’s contribution is both practical, but also methodological from this vantage point, especially in an African context where there is much critique of ‘outsider research’, yet little pro-active articulation of what insider (in this case, formative intervention) research may look like. , Thesis (PhD) -- Faculty of Education, Education, 2021
- Full Text:
- Date Issued: 2021-10-29
Stepping into history : biography as approaches to contemporary South African choreography with specific reference to Bessie's Head (2000) and Miss Thandi (2002)
- Snyman, Johannes Hendrik Bailey
- Authors: Snyman, Johannes Hendrik Bailey
- Date: 2003
- Subjects: Head, Bessie, 1937-1986 , Maqoma, Gregory -- Miss Thandi , Derrida, Jacques -- Criticism and interpretation , Biography , Choreography -- South Africa -- History
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2154 , http://hdl.handle.net/10962/d1004678
- Description: This mini-thesis is located in historical discursive practices, choreographing history, biography as a source for making dance in South Africa and choreographic transformations in South African choreography since the 1994 democratic elections. Derridian concepts of deconstruction will be referenced in an attempt to focus the argument of this research, which comments on choreographic transformations since 1994, by subverting the influence of the 'violent hierarchies' enforced by the apartheid regime on South African cultural life and choreographic identity. The researcher draws on these considerations in order to explore the hybrid nature of South African choreography that has emerged since 1994. Chapter one examines the fallacious nature of historical discourse through a consideration and application of Derrida's notions of deconstruction and fabrication. Chapter two explores the notion of choreographing history in theatre through a focus on the objective/subjective fallacy and the history of the body as a textual medium. Chapter three focuses the study specifically in biography as a discourse within the idea of theatre. This approach to biography can be encapsulated by the phrase 'telling lives'. This chapter also explores the relationship between the traditional binaries of writing as a purely cerebral act and choreography as a purely visceral experience. Chapter four brings the focus to the specific post-apartheid South African context. This chapter considers the hybrid forms of dance emerging in South Africa as well as the notion of protest in relation to theatre and dance. The final chapter is an investigation and analysis of two choreographic works created by South African choreographers since 1994 in relation to biography and concepts of deconstruction. These works are Gary Gordon's Bessie's Head (2000) and Gregory Maqoma's Miss Thandi (2002). The focus of the analysis also reveals the inherent difficulty in objective interpretation, and considers the problematics of collaboration and autobiography when choreographing within a biographical context.
- Full Text:
- Date Issued: 2003
- Authors: Snyman, Johannes Hendrik Bailey
- Date: 2003
- Subjects: Head, Bessie, 1937-1986 , Maqoma, Gregory -- Miss Thandi , Derrida, Jacques -- Criticism and interpretation , Biography , Choreography -- South Africa -- History
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2154 , http://hdl.handle.net/10962/d1004678
- Description: This mini-thesis is located in historical discursive practices, choreographing history, biography as a source for making dance in South Africa and choreographic transformations in South African choreography since the 1994 democratic elections. Derridian concepts of deconstruction will be referenced in an attempt to focus the argument of this research, which comments on choreographic transformations since 1994, by subverting the influence of the 'violent hierarchies' enforced by the apartheid regime on South African cultural life and choreographic identity. The researcher draws on these considerations in order to explore the hybrid nature of South African choreography that has emerged since 1994. Chapter one examines the fallacious nature of historical discourse through a consideration and application of Derrida's notions of deconstruction and fabrication. Chapter two explores the notion of choreographing history in theatre through a focus on the objective/subjective fallacy and the history of the body as a textual medium. Chapter three focuses the study specifically in biography as a discourse within the idea of theatre. This approach to biography can be encapsulated by the phrase 'telling lives'. This chapter also explores the relationship between the traditional binaries of writing as a purely cerebral act and choreography as a purely visceral experience. Chapter four brings the focus to the specific post-apartheid South African context. This chapter considers the hybrid forms of dance emerging in South Africa as well as the notion of protest in relation to theatre and dance. The final chapter is an investigation and analysis of two choreographic works created by South African choreographers since 1994 in relation to biography and concepts of deconstruction. These works are Gary Gordon's Bessie's Head (2000) and Gregory Maqoma's Miss Thandi (2002). The focus of the analysis also reveals the inherent difficulty in objective interpretation, and considers the problematics of collaboration and autobiography when choreographing within a biographical context.
- Full Text:
- Date Issued: 2003
Development of an in-situ ß-D-Glucuronidase diagnostic moraxella-based biosensor for potential application in the monitoring of water polluted by faecal material in South Africa
- Authors: Togo, Chamunorwa Aloius
- Date: 2007
- Subjects: Water quality management -- South Africa Water quality bioassay -- South Africa Sewage sludge -- South Africa -- Management Water -- Purification -- Biological treatment -- South Africa Biosensors
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3947 , http://hdl.handle.net/10962/d1004006
- Description: The prevention of outbreaks of waterborne diseases remains a major challenge to public health service providers globally. One of the major obstacles in this effort is the unavailability of on-line and real-time methods for rapid monitoring of faecal pollution to facilitate early warning of contamination of drinking water. The main objective of this study was to develop a β-glucuronidase (GUD)-based method that could be used for the on-line and real-time monitoring of microbial water quality. GUD is a marker enzyme for the faecal indicator bacteria Escherichia coli. This enzyme breaks down the synthetic substrate p-nitrophenyl-β-D-glucuronide (PNPG) to D-glucuronic acid and p-nitrophenol (PNP), which turns yellow under alkaline pH. The enzymatically produced PNP was used to detect GUD activity. In situ GUD assays were performed using running and stagnant water samples from the Bloukrans River, Grahamstown, South Africa. The physico-chemical properties of environmental GUD were determined, after which a liquid bioprobe and a microbial biosensor modified with Moraxella 1A species for the detection of the enzyme activity were developed. In order to determine the reliability and sensitivity of these methods, regression analyses for each method versus E. coli colony forming units (CFU) were performed. The storage stabilities of the bioprobe and biosensor were also investigated. The physico-chemical properties of in situ GUD were different from those of its commercially available counterpart. The temperature optimum for the former was between 35 and 40 °C while for the latter it was 45 °C. Commercial (reference) GUD had a pH optimum of 8.0 while the environmental counterpart exhibited a broad pH optimum of between pH 5.0 and 8.0. The liquid bioprobe had a limit of detection (LOD) of GUD activity equivalent to 2 CFU/100 ml and a detection time of 24 h. The method was less labour intensive and costly than the culturing method. The liquid bioprobe was stable for at least four weeks at room temperature (20 ± 2 °C). The biosensor was prepared by modifying a glassy carbon electrode with PNP degrading Moraxella 1A cells. The biosensor was 100 times more sensitive and rapid (5-20 min) than the spectrophotometric method (24 h), and was also able to detect GUD activity of viable but non-culturable cells. Thus it was more sensitive than the culturing method. Furthermore, the biosensor was selective and costeffective. The possibility of using a Pseudomonas putida JS444 biosensor was also investigated, but it was not as sensitive and selective as the Moraxella 1A biosensor. The Moraxella biosensor, therefore, offered the best option for on-line and real-time microbial water quality monitoring in South African river waters and drinking water supplies.
- Full Text:
- Date Issued: 2007
- Authors: Togo, Chamunorwa Aloius
- Date: 2007
- Subjects: Water quality management -- South Africa Water quality bioassay -- South Africa Sewage sludge -- South Africa -- Management Water -- Purification -- Biological treatment -- South Africa Biosensors
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3947 , http://hdl.handle.net/10962/d1004006
- Description: The prevention of outbreaks of waterborne diseases remains a major challenge to public health service providers globally. One of the major obstacles in this effort is the unavailability of on-line and real-time methods for rapid monitoring of faecal pollution to facilitate early warning of contamination of drinking water. The main objective of this study was to develop a β-glucuronidase (GUD)-based method that could be used for the on-line and real-time monitoring of microbial water quality. GUD is a marker enzyme for the faecal indicator bacteria Escherichia coli. This enzyme breaks down the synthetic substrate p-nitrophenyl-β-D-glucuronide (PNPG) to D-glucuronic acid and p-nitrophenol (PNP), which turns yellow under alkaline pH. The enzymatically produced PNP was used to detect GUD activity. In situ GUD assays were performed using running and stagnant water samples from the Bloukrans River, Grahamstown, South Africa. The physico-chemical properties of environmental GUD were determined, after which a liquid bioprobe and a microbial biosensor modified with Moraxella 1A species for the detection of the enzyme activity were developed. In order to determine the reliability and sensitivity of these methods, regression analyses for each method versus E. coli colony forming units (CFU) were performed. The storage stabilities of the bioprobe and biosensor were also investigated. The physico-chemical properties of in situ GUD were different from those of its commercially available counterpart. The temperature optimum for the former was between 35 and 40 °C while for the latter it was 45 °C. Commercial (reference) GUD had a pH optimum of 8.0 while the environmental counterpart exhibited a broad pH optimum of between pH 5.0 and 8.0. The liquid bioprobe had a limit of detection (LOD) of GUD activity equivalent to 2 CFU/100 ml and a detection time of 24 h. The method was less labour intensive and costly than the culturing method. The liquid bioprobe was stable for at least four weeks at room temperature (20 ± 2 °C). The biosensor was prepared by modifying a glassy carbon electrode with PNP degrading Moraxella 1A cells. The biosensor was 100 times more sensitive and rapid (5-20 min) than the spectrophotometric method (24 h), and was also able to detect GUD activity of viable but non-culturable cells. Thus it was more sensitive than the culturing method. Furthermore, the biosensor was selective and costeffective. The possibility of using a Pseudomonas putida JS444 biosensor was also investigated, but it was not as sensitive and selective as the Moraxella 1A biosensor. The Moraxella biosensor, therefore, offered the best option for on-line and real-time microbial water quality monitoring in South African river waters and drinking water supplies.
- Full Text:
- Date Issued: 2007