Studies on the fermentation of molasses by Clostridium acetobutylicum
- Authors: Barber, Jennifer Mary
- Date: 1978
- Subjects: Molasses , Clostridium acetobutylicum , Fermentation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4084 , http://hdl.handle.net/10962/d1007611 , Molasses , Clostridium acetobutylicum , Fermentation
- Description: The bacterium Clostridium acetobutylicum produces acetone and n [subscript] - butanol from molasses in an industrial fermentation system. Although the bacterium has been cultured in liquid media it does not grow well on agar plates and requires high concentrations of hydrogen. Pretreatment of agar plates with bovine catalase improves growth on agar media. The bacteria produce an area of clearing (halo) on Potato agar plates due to butyric acid (the precursor of n [subscript]-butanol) and ß -amylase production. This characteristic will be used as a plate screening assay for the selection of high solvent producing mutants. A laboratory scale fermentation system was developed and detailed studies including pH, turbidity and cell morphology changes, and the details of solvent production were undertaken. The fermentation was optimized for mutant selection. The production of normal solvent yields by isolated clones is required for the mutant selection programme. Studies revealed that sporulation of the clones increased their solvent yield although solvent yields were still lower than normal. Efficient sporulation is therefore a prerequisite for clone fermentation. The origin of the phage infection during the factory outbreak was determined and resistant clones obtained. The presence of a bacteriocin-like toxin causing decreases in turbidity was identified during the final fermentation stage. The strain sensitivity, optimum conditions for stability as well as the kinetics of inactivation and lethality have been investigated. Preliminary characterization and purification studies indicate the proteinaceous nature of the toxin. , KMBT_363
- Full Text:
- Date Issued: 1978
Development of an artificial weaning diet for the South African abalone, Haliotis midae (Haliotidae: Gastropoda)
- Authors: Knauer, Jens
- Date: 1994
- Subjects: Abalone culture -- Research -- South Africa , Ichthyology , Abalones
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5204 , http://hdl.handle.net/10962/d1004099 , Abalone culture -- Research -- South Africa , Ichthyology , Abalones
- Description: An adequate supply of diatoms during the weaning stage (generally 5 - 10 mm shell length (SL)) is one of the primary constraints to the commercial culture of the South African abalone, Haliotis midae. Because of the seriousness of the problem, a project aimed at the development of an artificial weaning diet was initiated. Initially, the chemical composition (proximate composition, amino acid, fatty acid and mineral element profile) of juvenile H. midae was analyzed, as a general lack of such information was identified in a review. Due to the lack of knowledge on the nutritional requirements of H. midae, the formulation of the weaning diet was based on the essential amino acid (EAA) pattern of the shucked tissue, and the known nutrient requirements of haliotids. Subsequently, a water stable gel and pellet form of the diet were developed. The best water stability of a gel was obtained with a 1:3 agar/gelatine mixture which retained 70.7 ± 2.7 % of its dry weight after 24 h. Starch based pellets, however, retained 89.0 ± 0.6 % of their dry weight after 24 h. In a comparative growth trial, pellets produced a significantly better increase in SL and weight than gels after only 15 days. This was probably due to the better water stability of pellets, which resulted in a better nutritional quality than in gels. The feeding behaviour on both forms of the diet did not differ. Activity patterns were exclusively nocturnal and feeding frequency was consistently low. The percentage composition of the pelleted weaning diet, on a dry weight basis, was 5 % casein, 15 % gelatine, 15 % fish meal, 10 % Spirulina spp., 2.5 % fish oil, 2.5 % sunflower oil, 21.0 % dextrin, 23.0 % starch, 4.0 % of a mineral and 2.0 % of a vitamin mixture. The correlation coefficient between the EAA pattern of H. midae and the dietary EAA pattern was r⁷= 0.8989. Pellets were fed to juveniles in a 30 day growth trial to study the effect of photoperiod (12, 16, 20 and 23 hours of darkness) on growth and general nutritional parameters. A comparative experiment feeding diatoms was conducted under a 12hL: 12hD light regime at the same time. The SL and weight of the juveniles did not increase significantly with an increase in hours of darkness. The growth of juveniles fed on pellets did not differ significantly from those fed on diatoms. Percentage feed consumption (PFC), percentage feeding rate (PFR), feed conversion ratio (FCR), protein efficiency ratio (PER) and percentage protein deposited (PPD) were determined for the animals fed on pellets. None of the parameters were significantly affected by photoperiod. However, there were trends in that PFC increased with longer periods of darkness, while PPD decreased. The FCRs (0.44 ± 0.04 to 0.60 ± 0.19) and PERs (5.06 ± 1.74 to 6.64 ± 0.77) indicated that juveniles used the feed, and in particular the protein, very efficiently. Photoperiod did not have an effect on the specific activity of the digestive enzymes amylase, protease and lipase. The specific activity of amylase in the juveniles fed on diatoms was significantly higher than in the pellet fed groups. This was surprising as the main carbohydrate of diatoms is the ß-(l-3) glucan chrysolaminarin, and not starch, a ß-(l-4) glucan. Protease specific activity, on the other hand, was significantly higher in the pellet fed groups, indicating an ability to adapt to the high protein content in the artificial diet (35.48 %), compared to diatoms which had a protein content of 5 %. The specific activity of lipase did not differ significantly between groups, probably because of a similar lipid concentration (5 - 10 %) in diatoms and pellets. Finally, the effect of stocking density, ranging from 1250 to 10,000 juveniles/m2, on the growth of juveniles was evaluated. A model of hatchery productivity was developed based on this investigation. Hatchery productivity was defined as the number of juveniles per unit space reared through to the grow-out stage per unit time. The model predicted that maximum productivity would be achieved at a stocking density of 10,000 juveniles/m2. The results have shown that H. midae can be successfully weaned on an artificial diet, as the growth on the diet was not significantly different to growth obtained on diatoms. Long-term growth trials are needed to confirm these results. The importance of standardized experiments on the nutritional requirements and digestibility of abalone was emphasized. The importance of improved artificial diets, optimal culture conditions, as well as the application of biotechnological techniques to further abalone aquaculture was highlighted.
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- Date Issued: 1994
Synthesis of zinc phthalocyanine derivatives for possible use in photodynamic therapy
- Authors: Matlaba, Pulane Maseleka
- Date: 2003
- Subjects: Photochemotherapy , Electrochemistry , Phthalocyanines , Zinc
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4374 , http://hdl.handle.net/10962/d1005039 , Photochemotherapy , Electrochemistry , Phthalocyanines , Zinc
- Description: The synthesis of symmetrically and unsymmetrically substituted zinc phthalocyanines (ZnPc) derivatives is done according to reported procedures. The unsymmetrical ZnPc derivatives are synthesized by ring expansion of sub-phthalocyanine complexes. Ring substitution is effected with tert-butyl phenol, naphthol, and hydroxybenzoic acid. Comparison of the redox potentials for the complexes substituted with varying numbers of tert-butyl phenol: 1, 2, 3, 6 and 8 show that the complex with the highest number of substituents are more difficult to oxidize and easier to reduce. Water soluble sulphonated ZnPc (ZnPcSn) was prepared. The possibility of using axial ligation to increase the solubility and the photochemical activity of sulphotnated ZnPc in aqueous solutions was investigated. Pyridine, aminopyridyl and bipyridyl were used as axial ligands. When bipyridyl was used as the axial ligand, solubility of the ZnPcSn increased, shown by the increase in the Q-band of the monomer species in solution and the singlet oxygen quantum yields was relatively higher than that of the unligated ZnPcSn. The singlet oxygen quantum yields by the various complexes in DMF using diphenylisobenzofuran as a chemical quencher for organic solvent were determined. Singlet oxygen quantum yields for the unsymmetrically ring substituted complexes range from 0.22 to 0.68. Photobleaching quantum yields are in the order of 10-5, which means that the complexes are relatively photostable.
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- Date Issued: 2003
Evaluation of incidence of Mycobacterium tuberculosis complex associated with soil, hayfeed and water in three agricultural facilities in Amathole District Municipality in the Eastern Cape Province, South Africa
- Authors: Ntloko, Athini
- Date: 2015
- Subjects: Mycobacterium tuberculosis -- South Africa -- Eastern Cape Drug resistance in microorganisms Mycobacterial diseases
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/2689 , vital:27993
- Description: Mycobacterium bovis and other species of Mycobacterium tuberculosis complex (MTBC) can result to a zoonotic infection known as Bovine tuberculosis (bTB). MTBC has members that may contaminate an extensive range of hosts, including wildlife. Diverse wild species are known to cause disease in domestic livestock and are acknowledged as TB reservoirs. It has been a main study worldwide to deliberate on bTB risk factors as a result some studies focused on particular parts of risk factors such as wildlife and herd management. The objectives of this study were to design questionnaires from commercial farms and smallholding farms; isolate and identify MTBC from collected samples using culture and PCR assays recovered from Fort Hare, Middledrift and Seven star dairy farms; and assessing genotypic drug resistance through detection of mutations conferring resistance to INH and RMP associated with first line treatment for MTBC infection. Questionnaires were administered to thirty (30) smallholding farm owners in the two villages (kwaMasele and Qungqwala) and three (3) three commercial farms (Fort Hare dairy farm, Middledrift dairy farm and Seven-star dairy farm). Detection of M. tuberculosis complex was achieved by Polymerase Chain Reaction using primers for IS6110; whereas a genotypic drug resistance mutation was detected using Genotype MTBDRplus assays. Nine percent (9 percent) of respondents had more than 40 cows in their herd, while 60 percent reported between 10 and 20 cows in their herd. Relationship between farm size and vaccination for TB differed from forty-one percent (41 percent) being the highest to the least five percent (5 percent). The highest number of respondents who knew about relationship between TB cases and cattle location was ninety-one percent (91 percent). Approximately fifty-one percent (51 percent) of respondents had knowledge about wild life access to the farms. Relationship between import of cattle and farm size ranged from nine percent (9 percent) to thirty-five percent (35 percent). Cattle sickness in relation to farm size differed from forty-three (43 percent) being the highest to the least three percent (3 percent); while thirty-three percent (33 percent) of respondents had knowledge about health management. Respondents with knowledge about the occurrence of TB infections in farms were forty-eight percent (48 percent). The frequency of DNA isolation from samples ranged from the highest forty-five percent (45 percent) from water to the least twenty-two percent (22 percent) from soil. Fort Hare dairy farm had the highest number of positive samples forty-four percent (44 percent) from water samples; whereas Middledrift dairy farm had the lowest positive from water, seventeen percent (17 percent). Twelve (22 percent) out of 55 isolates showed resistance to INH and RMP that is, multi-drug resistance (MDR) and nine percent (9 percent) were sensitive to either INH or RMP. The mutations at rpoB gene differed from 58 percent being the highest to the least (23 percent). Fifty-seven percent (57 percent) of samples showed a S315T1 mutation while only 14 percent possessed a S531L in the katG gene. The highest inhA mutations were detected in T8A (80 percent) eighty percent and the least was observed in A16G (17 percent). The results of this study reveals that risk factors for bTB in cattle and dairy farm workers is a serious issue abound in the Eastern Cape of South Africa; with the possibility of widespread dissemination of multidrug resistant determinants in MTBC from the environment.
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- Date Issued: 2015
Detecting derivative malware samples using deobfuscation-assisted similarity analysis
- Authors: Wrench, Peter Mark
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/383 , vital:19954
- Description: The overwhelming popularity of PHP as a hosting platform has made it the language of choice for developers of Remote Access Trojans (RATs or web shells) and other malicious software. These shells are typically used to compromise and monetise web platforms by providing the attacker with basic remote access to the system, including _le transfer, command execution, network reconnaissance, and database connectivity. Once infected, compromised systems can be used to defraud users by hosting phishing sites, performing Distributed Denial of Service attacks, or serving as anonymous platforms for sending spam or other malfeasance. The vast majority of these threats are largely derivative, incorporating core capabilities found in more established RATs such as c99 and r57. Authors of malicious software routinely produce new shell variants by modifying the behaviours of these ubiquitous RATs, either to add desired functionality or to avoid detection by signature-based detection systems. Once these modified shells are eventually identified (or additional functionality is required), the process of shell adaptation begins again. The end result of this iterative process is a web of separate but related shell variants, many of which are at least partially derived from one of the more popular and influential RATs. In response to the problem outlined above, the author set out to design and implement a system capable of circumventing common obfuscation techniques and identifying derivative malware samples in a given collection. To begin with, a decoder component was developed to syntactically deobfuscate and normalise PHP code by detecting and reversing idiomatic obfuscation constructs, and to apply uniform formatting conventions to all system inputs. A unified malware analysis framework, called Viper, was then extended to create a modular similarity analysis system comprised of individual feature extraction modules, modules responsible for batch processing, a matrix module for comparing sample features, and two visualisation modules capable of generating visual representations of shell similarity. The principal conclusion of the research was that the deobfuscation performed by the decoder component prior to analysis dramatically improved the observed levels of similarity between test samples. This in turn allowed the modular similarity analysis system to identify derivative clusters (or families) within a large collection of shells more accurately. Techniques for isolating and re-rendering these clusters were also developed and demonstrated to be effective at increasing the amount of detail available for evaluating the relative magnitudes of the relationships within each cluster.
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- Date Issued: 2016
Using data mining techniques for the prediction of student dropouts from university science programs
- Authors: Vambe, William Tichaona
- Date: 2016
- Subjects: Data mining Dropout behavior, Prediction of
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/12314 , vital:39252
- Description: Data Mining has taken a center stage in education for addressing student dropout challenges as it has become one of the major threat affecting Higher Educational Institutes (HEIs). Being able to predict students who are likely to dropout helps the university to assist those facing challenges early. This will results in producing more graduates with the intellectual capital who will provide skills in the industries, hence addressing the major challenge of skill shortage being faced in South Africa. Studies and researches as purported in literature have been done to address this major threat of dropout challenge by using the theoretical approach which banked on Tinto’s model, followed by the traditional and statistical approach. However, the two lacked accuracy and the automation aspect which makes them difficult and time-consuming to use as they require to be tested periodically for them to be validated. Recently data mining has become a vital tool for predicting non-linear phenomenon including where there is missing data and bringing about accuracy and automation aspect. Data mining usefulness and reliability assessment in education made it possible to be used for prediction by different researchers. As such this research used data mining approach that integrates classification and prediction techniques to analyze student academic data at the University of Fort Hare to create a model for student dropout using preentry data and university academic performance of each student. Following Knowledge Discovery from Database (KDD) framework, data for the students enrolled in the Bachelor of Science programs between 2003 and 2014 was selected. It went through preprocessing and transformation as to deal with the missing data and noise data. Classification algorithms were then used for student characterization. Decision trees (J48) which are found in Weka software were used to build the model for data mining and prediction. The reason for choosing decision trees was it’s ability to deal with textual, nominal and numeric data as was the case with our input data and because they have good precision.The model was then trained using a train data set, validated and evaluated with another data set. Experimental results demonstrations that data mining is useful in predicting students who have chances to drop out. A critical analysis of correctly classifying instances, the confusion matrix and ROC area shows that the model can correctly classify and predict those who are likely to dropout. The model accuracy was 66percent which is a good percentage as supported in literature which means the results produced can be reliably used for assessment and make strategic decisions. Furthermore, the model took a matter of seconds to compute the results when supplied with 400 instances which prove that it is effective and efficient. Grounding our conclusion from these experimental results, this research proved that Data Mining is useful for bringing about automation, accuracy in prediction of student dropouts and the results can be reliably depended on for decision making by faculty managers who are the decision makers.
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- Date Issued: 2016
Protected area expansion and conservation stewardship in the Olifants Catchment: mechanisms, patterns and benefits
- Authors: Coetzer, Crystal Jeanne
- Date: 2018
- Subjects: Biodiversity conservation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30006 , vital:30808
- Description: State Conservation Areas (SCAs), as state-owned and -run parks, form the foundation of recognised conservation actions. However, park expansion on the scale required to meet urgent conservation targets is limited by state budgets and parks are increasingly framed in the context of advancing broader societal needs. Motivating for the need to assess the efficacy of alternative conservation strategies, as both contrasting governance and legal mechanisms, this study aimed to rapidly assess the role of private land conservation (PLC) strategies in expanding protection. In particular, this included the role of emerging stewardship approaches, by using semi-structured interviews with park implementers on a national scale. Evaluating the biodiversity and ecosystem service representation and complementarity of contrasting conservation strategies on a catchment scale, using open-source spatial data was employed. Questionnaires tested park managers’ perceptions of benefits across different strategies in a conservation-oriented landscape. Results indicate a strategic shift toward PLC strategies to expand parks in the form of formalised, well-planned and supported contractual and stewardship agreements. SCAs are vital baselines for biodiversity and ecosystem service representation in the catchment with a variety of private mechanisms supplementing protection, especially in highly contested areas. The perceived benefits rated by managers revealed interesting links between benefits and contrasting governance types, legal mechanisms, legal status, size and age of reserves. State parks may be more relevant for generating socio-cultural benefits, while private parks, through the need to remain economically viable, valued a diverse range of socio-economic benefits. Informal conservation areas formed integral parts of the conservation-orientated landscape, rating benefits equally to more secure mechanisms. Private land must be incorporated into conservation through diverse mechanisms to meet the range of mutually exclusive conservation objectives of the 21st century.
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- Date Issued: 2018
Zoning the Southwestern Indian Ocean to mitigate impacts from ocean-based hydrocarbon exploration and production on sea turtles
- Authors: Pretorius, Dirk
- Date: 2019
- Subjects: Ocean zoning , Marine ecology -- Indian Ocean Sea turtles -- Indian Ocean Marine animals -- Ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43303 , vital:36787
- Description: The conflict between sea turtles and the numerous socio-economic developments in the Southwestern Indian Ocean (SWIO) are set to intensify as countries are looking to develop their ocean-based economies. The Hydrocarbon Exploration and Production (HEP) industry is of particular importance, since many of the SWIO governments view it as catalyst for development. This has raised concerns about potentially significant environmental impacts from the HEP industry, to sea turtles and their habitats, based on international examples where sea turtles have been severely negatively impacted upon, like the Deepwater Horizon spill in the Gulf of Mexico. Given that the four sea turtles species in the SWIO are listed on the IUCN Red List of threatened species, the aim of this study was to derive priority areas for sea turtles in the face of HEP, that could be used in an ocean zoning strategy for sustainable economic development of HEP in the SWIO region. To achieve this, the study spatially represented the main life-history stages of sea turtles, i.e. the breeding, migrating and foraging areas of Caretta caretta (loggerhead turtles), Dermochelys coriacea (leatherback turtles), Chelonia mydas (green turtles) and Eretmochelys imbricata (hawksbill turtles), within a telemetry derived distribution for each species. This spatial representation was used to quantify the extent of Marine Protected Areas (MPAs) conserving sea turtles in the SWIO, which revealed that sea turtle breeding areas were well represented in MPAs, including C. caretta (~40 %), C. mydas (~53 %), E. imbricata (~59 %) and D. coriacea (~22 %), the latter being least protected by MPAs during breeding, possibly due to a far greater extent of their internesting areas than the other three species. MPA coverage of breeding areas could be positively correlated to the increasing population trends of C. caretta and C. mydas in the SWIO, and therefore the assumption was made that increasing population trends of sea turtles are in part related to MPA protection of their breeding areas. In addition, the potential impacts on sea turtles from existing and proposed HEP developments were assessed and mapped by using a novel, species-specific rating index. The results revealed the extensive nature of potential water pollution impacts on sea turtles, constituting 16 of the top 28 most significant impacts from HEP on sea turtles. Other significant impacts on sea turtles associated with the HEP industry, included habitat destruction, light pollution and noise pollution. Importantly, this study found that ~70 % of all potential HEP impacts (irrespective of significance) on adult nesting sea turtles could be avoided if seasonal sea turtle movement during critical life stages are included as species-specific HEP mitigation measures. The data and maps on the main life-history stages of sea turtles, and the potential cumulative impacts from the HEP industry, were used in a Systematic Conservation Planning process, to derive a concept ocean zoning. As final outcome of this study, the concept ocean zoning highlighted areas where increased protection to sea turtles, and management of the conflict between sea turtles and the HEP industry, will be required if the HEP industry is to develop in a sustainable manner in the SWIO.
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- Date Issued: 2019