The biotechnology of effluent-grown Spirulina, and application in aquaculture nutrition
- Authors: Maart, Brenton Ashley
- Date: 1993
- Subjects: Aquaculture , Spirulina , Algae -- Biotechnology , Fishes -- Feeding and feeds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4050 , http://hdl.handle.net/10962/d1004111 , Aquaculture , Spirulina , Algae -- Biotechnology , Fishes -- Feeding and feeds
- Description: The biotechnology of production and utilisation of the cyanobacterium Spirulina has been well documented. Research has centred mainly on application in human and animal nutrition, and has been motivated by the high protein, vitamin, fatty acid and growth factor contents. The main obstacle in realising the full potential of this feed source has been the high production costs associated with its mass culture in defined media. The observation of blooms of Spirulina in tannery effluent evaporation ponds in Wellington, South Africa, prompted this investigation into the harvesting, and nutritional and toxicological evaluation of this potentially low-cost production system, with the ultimate aim of using the product in aquaculture rations. An investigation of the chemical gradient along the evaporation cascade showed a positive correlation between the prevailing chemical conditions and the dominant species populations. A standing crop of 9.5 tonnes/ha of Spirulina was found to be present in the latter alkaline ponds, characterised by relatively lower organic and sulphur contents. Initial harvesting of the biomass was achieved by the design, construction and implementation of a small-scale screen harvest, which yielded a 25 kg (dry weight) crop. A scale-up model was then designed, and implemented in a technical scale harvest, yielding a crop of 250 kg (dry weight). Both these harvests utilised the bloom of surface-autoflocculated biomass. Concentrated cell slurries were sun-dried on muslin beds, and milled to a coarse powder. An evaluation of the harvest revealed a chemical content similar to other published reports of defined media cultures, with the exception of the protein and amino acid contents. The observed lower levels of the latter two are almost certainly due to the sun-drying method employed, known to reduce the protein content due to thermal denaturation. Legislation demands the strict toxicological evaluation of new protein sources, and because of the effluent-nature of the growth medium of this source of Spirulina, its viability lies only in the application as an animal feed or supplement. A range of toxicological tests were chosen that were targeted to elucidate the possible toxicological constraints of this effluentgrown source of protein in animal nutrition. The nucleic acid and pesticide contents of the harvested biomass were within the prescribed safety ranges. Atomic absorption showed minimal accumulation of minerals and heavy metals from the effluent. A bioassay with the brine shrimp Anemia salina showed that the biomass contained no toxicologically active water-soluble components. A short term feeding trial with new-born chicks showed that supplementation with Spirulina had no effect on the growth rates and feed conversion ratios of the different feeding groups. Pathological analyses showed that the liver was the only target organ to elicit a change in response to supplementation of the diets with Spirulina. A general decrease in liver weight was noted, with Cu, Ca, Fe and Zn being significantly accumulated. A histopathological examination however, showed no cellular and functional aberration from the control animals. The toxicological analyses gave the preliminary safe go-ahead for the evaluation of effluent-grown Spirulina in aquaculture nutrition. The South African abalone Haliotis midae, and the rainbow trout Oncorhynchus mykiss were chosen as representative species of edible cultured organisms. The technology for the culture of the perlemoen abalone is being established in South Africa, with the main area of research being the development of an artificial diet for high density culture. A 40 day growth trial demonstrated that lower concentrations of Spirulina supplemented to an agar-based fishmeal diet resulted in growth rates and feed conversion ratios similar to the control fishmeal and purified-casein diets, and thus has application potential in the nutrition of this high-cost marine delicacy. The aquaculture technology of freshwater rainbow trout is already well established. An eight week feeding trial with various concentrations of Spirulina showed that this effluent-grown protein source can partially replace fishmeal in semi-purified diets. Fish fed Spirulina did not exhibit decisive manifestations of toxicity, as determined in a histopathological study. In addition, Spirulina supplementation resulted in enhanced colouration of the skin and flesh, which may have implications in the aesthetic marketing of this sought-after table fish. The primary aim of this preliminary investigation thus concerned the determination of the biotechnological potential of this effluent-source of Spirulina. A technology transfer from the economically unfeasible defined-media culture was implemented. This project is ultimately aimed as a contribution towards the treatment of tannery wastewater, by the removal of contaminants from the effluent in the form of organic biomass.
- Full Text:
- Date Issued: 1993
- Authors: Maart, Brenton Ashley
- Date: 1993
- Subjects: Aquaculture , Spirulina , Algae -- Biotechnology , Fishes -- Feeding and feeds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4050 , http://hdl.handle.net/10962/d1004111 , Aquaculture , Spirulina , Algae -- Biotechnology , Fishes -- Feeding and feeds
- Description: The biotechnology of production and utilisation of the cyanobacterium Spirulina has been well documented. Research has centred mainly on application in human and animal nutrition, and has been motivated by the high protein, vitamin, fatty acid and growth factor contents. The main obstacle in realising the full potential of this feed source has been the high production costs associated with its mass culture in defined media. The observation of blooms of Spirulina in tannery effluent evaporation ponds in Wellington, South Africa, prompted this investigation into the harvesting, and nutritional and toxicological evaluation of this potentially low-cost production system, with the ultimate aim of using the product in aquaculture rations. An investigation of the chemical gradient along the evaporation cascade showed a positive correlation between the prevailing chemical conditions and the dominant species populations. A standing crop of 9.5 tonnes/ha of Spirulina was found to be present in the latter alkaline ponds, characterised by relatively lower organic and sulphur contents. Initial harvesting of the biomass was achieved by the design, construction and implementation of a small-scale screen harvest, which yielded a 25 kg (dry weight) crop. A scale-up model was then designed, and implemented in a technical scale harvest, yielding a crop of 250 kg (dry weight). Both these harvests utilised the bloom of surface-autoflocculated biomass. Concentrated cell slurries were sun-dried on muslin beds, and milled to a coarse powder. An evaluation of the harvest revealed a chemical content similar to other published reports of defined media cultures, with the exception of the protein and amino acid contents. The observed lower levels of the latter two are almost certainly due to the sun-drying method employed, known to reduce the protein content due to thermal denaturation. Legislation demands the strict toxicological evaluation of new protein sources, and because of the effluent-nature of the growth medium of this source of Spirulina, its viability lies only in the application as an animal feed or supplement. A range of toxicological tests were chosen that were targeted to elucidate the possible toxicological constraints of this effluentgrown source of protein in animal nutrition. The nucleic acid and pesticide contents of the harvested biomass were within the prescribed safety ranges. Atomic absorption showed minimal accumulation of minerals and heavy metals from the effluent. A bioassay with the brine shrimp Anemia salina showed that the biomass contained no toxicologically active water-soluble components. A short term feeding trial with new-born chicks showed that supplementation with Spirulina had no effect on the growth rates and feed conversion ratios of the different feeding groups. Pathological analyses showed that the liver was the only target organ to elicit a change in response to supplementation of the diets with Spirulina. A general decrease in liver weight was noted, with Cu, Ca, Fe and Zn being significantly accumulated. A histopathological examination however, showed no cellular and functional aberration from the control animals. The toxicological analyses gave the preliminary safe go-ahead for the evaluation of effluent-grown Spirulina in aquaculture nutrition. The South African abalone Haliotis midae, and the rainbow trout Oncorhynchus mykiss were chosen as representative species of edible cultured organisms. The technology for the culture of the perlemoen abalone is being established in South Africa, with the main area of research being the development of an artificial diet for high density culture. A 40 day growth trial demonstrated that lower concentrations of Spirulina supplemented to an agar-based fishmeal diet resulted in growth rates and feed conversion ratios similar to the control fishmeal and purified-casein diets, and thus has application potential in the nutrition of this high-cost marine delicacy. The aquaculture technology of freshwater rainbow trout is already well established. An eight week feeding trial with various concentrations of Spirulina showed that this effluent-grown protein source can partially replace fishmeal in semi-purified diets. Fish fed Spirulina did not exhibit decisive manifestations of toxicity, as determined in a histopathological study. In addition, Spirulina supplementation resulted in enhanced colouration of the skin and flesh, which may have implications in the aesthetic marketing of this sought-after table fish. The primary aim of this preliminary investigation thus concerned the determination of the biotechnological potential of this effluent-source of Spirulina. A technology transfer from the economically unfeasible defined-media culture was implemented. This project is ultimately aimed as a contribution towards the treatment of tannery wastewater, by the removal of contaminants from the effluent in the form of organic biomass.
- Full Text:
- Date Issued: 1993
The effect of hydrostatic carbon dioxide pressure and extracellular ethanol on the performance of the yeast strain Saccharomyces cerevisiae during fermentation
- Authors: Longden, Nicholas Guy
- Date: 1993
- Subjects: Brewing -- Microbiology , Yeast , Fermentation , Saccharomyces cerevisiae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4044 , http://hdl.handle.net/10962/d1004105 , Brewing -- Microbiology , Yeast , Fermentation , Saccharomyces cerevisiae
- Description: The brewing industry constantly experiences problems in trying to maintain the quality of beer produced. Unfavourable conditions during fermentation may alter the performance of the yeast strain Saccharomyces cerevisiae, resulting in a "poor" end-product. It has been established that high concentrations of extracellular ethanol, when added to the fermentation medium inhibit yeast activity. It has been recently suggested that increased carbon dioxide pressure could inactivate the yeast activity adding to further brewing problems. The aim of this study was to investigate the effect of extracellular carbon dioxide pressure and ethanol addition, on yeast performance when added to a fermentation medium, and to establish whether an inhibitory relationship existed between ethanol and carbon dioxide pressure, when combined and added to the fermentation medium. Dissolved C0₂ in the medium, medium pH and substrate utilisation were analysed daily during a fermentation, as were membrane fatty acid composition. These parameters were used to assess the effect of ethanol and carbon dioxide on the yeast performance and consequently the final end-product. Supplementing the medium with extracellular ethanol, even as low as 5%, was shown to inhibit yeast performance during fermentation. This effect was even more marked as the ethanol concentration was increased, with almost total inhibition of yeast activity occuring after the addition of 15% ethanol (v/v). A similar effect was observed when elevated C0₂ pressures were applied to the medium, and although low C0₂ pressures initially induced the synthesis of saturated yeast membrane fatty acids, elevated C0₂ pressures (greater than 1,0 atm.) was shown to follow a similar inhibitory trend, if not as dramatic, as ethanol. A combination of both ethanol and C0₂ pressure showed a further increase in the level of yeast inhibition, although the low C0₂ pressure appeared to initially inhibit the toxicity of ethanol on the yeast. Increasing the levels of the C0₂/ethanol treatment (1,0 atm.), showed a synergistic effect on yeast performance. The results of this study indicate that both extracellular ethanol and carbon dioxide do appear to inhibit yeast performance and affect membrane fatty acid composition of the cells by inhibiting the synthesis of the respective fatty acid. This affect has a significant bearing on the general metabolism of the yeast cell.
- Full Text:
- Date Issued: 1993
- Authors: Longden, Nicholas Guy
- Date: 1993
- Subjects: Brewing -- Microbiology , Yeast , Fermentation , Saccharomyces cerevisiae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4044 , http://hdl.handle.net/10962/d1004105 , Brewing -- Microbiology , Yeast , Fermentation , Saccharomyces cerevisiae
- Description: The brewing industry constantly experiences problems in trying to maintain the quality of beer produced. Unfavourable conditions during fermentation may alter the performance of the yeast strain Saccharomyces cerevisiae, resulting in a "poor" end-product. It has been established that high concentrations of extracellular ethanol, when added to the fermentation medium inhibit yeast activity. It has been recently suggested that increased carbon dioxide pressure could inactivate the yeast activity adding to further brewing problems. The aim of this study was to investigate the effect of extracellular carbon dioxide pressure and ethanol addition, on yeast performance when added to a fermentation medium, and to establish whether an inhibitory relationship existed between ethanol and carbon dioxide pressure, when combined and added to the fermentation medium. Dissolved C0₂ in the medium, medium pH and substrate utilisation were analysed daily during a fermentation, as were membrane fatty acid composition. These parameters were used to assess the effect of ethanol and carbon dioxide on the yeast performance and consequently the final end-product. Supplementing the medium with extracellular ethanol, even as low as 5%, was shown to inhibit yeast performance during fermentation. This effect was even more marked as the ethanol concentration was increased, with almost total inhibition of yeast activity occuring after the addition of 15% ethanol (v/v). A similar effect was observed when elevated C0₂ pressures were applied to the medium, and although low C0₂ pressures initially induced the synthesis of saturated yeast membrane fatty acids, elevated C0₂ pressures (greater than 1,0 atm.) was shown to follow a similar inhibitory trend, if not as dramatic, as ethanol. A combination of both ethanol and C0₂ pressure showed a further increase in the level of yeast inhibition, although the low C0₂ pressure appeared to initially inhibit the toxicity of ethanol on the yeast. Increasing the levels of the C0₂/ethanol treatment (1,0 atm.), showed a synergistic effect on yeast performance. The results of this study indicate that both extracellular ethanol and carbon dioxide do appear to inhibit yeast performance and affect membrane fatty acid composition of the cells by inhibiting the synthesis of the respective fatty acid. This affect has a significant bearing on the general metabolism of the yeast cell.
- Full Text:
- Date Issued: 1993
The effect of short chain fatty acids on picornavirus replication
- Authors: Ismail-Cassim, Nazeem
- Date: 1993
- Subjects: Viruses -- Reproduction , Picornaviruses , Antiviral agents -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4030 , http://hdl.handle.net/10962/d1004090 , Viruses -- Reproduction , Picornaviruses , Antiviral agents -- Research
- Description: Picornavirus proteins VP1 to VP3 are exposed on the surface of the virus particle whereas VP4 is internal and modified at its amino terminus by the addition of myristic acid (Chow et al., 1987; Paul et al., 1987). Myristic acid occupies a position in the core of mature poliovirus particles; it has been suggested that it may be important for particle integrity or in the localization of the capsid protein precursor on the hydrophobic membranes during virion assembly (Chow et al., 1987). To determine the function of the amino-terminal myristylation of VP4 in picornaviruses, and to establish whether competition for the acylation site is a possible approach to antiviral chemotherapy, the effect of fatty acids on virus replication has been examined. Some fatty acids are able to enter picornavirus-infected cells and compete for the myristylation site on VP4. Unexpectedly, it was found that short chain fatty acids also inhibit an early event in the replication of bovine enterovirus (BEV) at concentrations which have no detectable effect on cellular macromolecular synthesis and cloning. These findings indicate that fatty acids inhibit cell-mediated uncoating. Short chain fatty acids inhibit the replication of bovine enterovirus but are almost ineffective against poliovirus type 1, coxsackievirus B5, encephalomyocarditis virus and human rhinovirus lB. Lauric acid binds to bovine enterovirus, thereby stabilizing the virus particle to heat degradation. Fatty acid-bound virions attach to susceptible cells but fail to undergo cell-mediated uncoating. The inhibitory effect is reversible with chloroform and may result from a hydrophobic interaction between the fatty acid and a specific site on the virus particie.
- Full Text:
- Date Issued: 1993
- Authors: Ismail-Cassim, Nazeem
- Date: 1993
- Subjects: Viruses -- Reproduction , Picornaviruses , Antiviral agents -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4030 , http://hdl.handle.net/10962/d1004090 , Viruses -- Reproduction , Picornaviruses , Antiviral agents -- Research
- Description: Picornavirus proteins VP1 to VP3 are exposed on the surface of the virus particle whereas VP4 is internal and modified at its amino terminus by the addition of myristic acid (Chow et al., 1987; Paul et al., 1987). Myristic acid occupies a position in the core of mature poliovirus particles; it has been suggested that it may be important for particle integrity or in the localization of the capsid protein precursor on the hydrophobic membranes during virion assembly (Chow et al., 1987). To determine the function of the amino-terminal myristylation of VP4 in picornaviruses, and to establish whether competition for the acylation site is a possible approach to antiviral chemotherapy, the effect of fatty acids on virus replication has been examined. Some fatty acids are able to enter picornavirus-infected cells and compete for the myristylation site on VP4. Unexpectedly, it was found that short chain fatty acids also inhibit an early event in the replication of bovine enterovirus (BEV) at concentrations which have no detectable effect on cellular macromolecular synthesis and cloning. These findings indicate that fatty acids inhibit cell-mediated uncoating. Short chain fatty acids inhibit the replication of bovine enterovirus but are almost ineffective against poliovirus type 1, coxsackievirus B5, encephalomyocarditis virus and human rhinovirus lB. Lauric acid binds to bovine enterovirus, thereby stabilizing the virus particle to heat degradation. Fatty acid-bound virions attach to susceptible cells but fail to undergo cell-mediated uncoating. The inhibitory effect is reversible with chloroform and may result from a hydrophobic interaction between the fatty acid and a specific site on the virus particie.
- Full Text:
- Date Issued: 1993
The regulation of Serotonin N-acetyltransferase in the rat pineal gland
- Authors: Olivieri, Gianfranco
- Date: 1993
- Subjects: Serotonin -- Research Pineal gland Acetyltransferases
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4051 , http://hdl.handle.net/10962/d1004112
- Description: The synthesis of the pineal hormone, melatonin, is finely regulated by the pineal enzyme serotonin N-acetyltransferase (NAT). In the absence of light, the activity of NAT is markedly enhanced by the release of nor-adrenaline from sympathetic nerve endings in the pineal. Exposure of animals to light during darkness causes a sudden and dramatic reduction in the activity of NAT. The present study investigated a possible mechanism for this sudden decline in NAT activity. These investigations included the determination of the effects of S-adenosylmethionine (SAM), adenosine nucleotides and calcium on NAT activity. In vitro experiments using SAM showed that pineals pre-incubated with SAM prior to adrenergic stimulation did not significantly alter NAT activity or pineal indoleamine metabolism. However, measurement of pineal cyclic AMP showed that SAM exposure reduced the adrenergic-induced rise in pineal cyclic AMP. Experiments using adenosine 5'-monophosphate (5'-AMP) showed that this nucleotide enhanced both dark- and isoproterenol-induced NAT activity. Adenosine 5'-triphosphate (A TP), on the other hand, reduced NAT activity with a concomitant reduction in pineal indoleamine metabolism. Exposure of isoproterenol-stimulated pineals in organ culture to propranolol resulted in a marked rise in ATP and adenosine 5'-diphosphate (ADP) synthesis accompanied by a decline in 5'-AMP levels as compared with pineals treated with isoproterenol alone. This then implies that exposure of animals to light could cause a change in pineal nucleotide levels. Since nucleotide levels are also controlled by calcium, experiments were carried out to determine the effect of calcium on pineal NAT activity. These experiments showed that ethyleneglycol-bis-N,N,N,N,-tetraacetic acid (EGTA) enhanced NAT activity whilst calcium reduced the activity in pineal homogenates, implying that calcium may act directly on NAT to regulate its activity. Exposure of pineal glands in organ culture to the calmodulin antagonist R24571 caused a rise in pineal cyclic AMP levels with a concomitant decrease in cAMP-phosphodiesterase activity. This was, however, accompanied by a decline in Nacetyl serotonin and melatonin synthesis. These findings implicate a number of factors in the regulation of pineal NAT activity. A mechanism for the regulation of pineal NAT is proposed.
- Full Text:
- Date Issued: 1993
- Authors: Olivieri, Gianfranco
- Date: 1993
- Subjects: Serotonin -- Research Pineal gland Acetyltransferases
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4051 , http://hdl.handle.net/10962/d1004112
- Description: The synthesis of the pineal hormone, melatonin, is finely regulated by the pineal enzyme serotonin N-acetyltransferase (NAT). In the absence of light, the activity of NAT is markedly enhanced by the release of nor-adrenaline from sympathetic nerve endings in the pineal. Exposure of animals to light during darkness causes a sudden and dramatic reduction in the activity of NAT. The present study investigated a possible mechanism for this sudden decline in NAT activity. These investigations included the determination of the effects of S-adenosylmethionine (SAM), adenosine nucleotides and calcium on NAT activity. In vitro experiments using SAM showed that pineals pre-incubated with SAM prior to adrenergic stimulation did not significantly alter NAT activity or pineal indoleamine metabolism. However, measurement of pineal cyclic AMP showed that SAM exposure reduced the adrenergic-induced rise in pineal cyclic AMP. Experiments using adenosine 5'-monophosphate (5'-AMP) showed that this nucleotide enhanced both dark- and isoproterenol-induced NAT activity. Adenosine 5'-triphosphate (A TP), on the other hand, reduced NAT activity with a concomitant reduction in pineal indoleamine metabolism. Exposure of isoproterenol-stimulated pineals in organ culture to propranolol resulted in a marked rise in ATP and adenosine 5'-diphosphate (ADP) synthesis accompanied by a decline in 5'-AMP levels as compared with pineals treated with isoproterenol alone. This then implies that exposure of animals to light could cause a change in pineal nucleotide levels. Since nucleotide levels are also controlled by calcium, experiments were carried out to determine the effect of calcium on pineal NAT activity. These experiments showed that ethyleneglycol-bis-N,N,N,N,-tetraacetic acid (EGTA) enhanced NAT activity whilst calcium reduced the activity in pineal homogenates, implying that calcium may act directly on NAT to regulate its activity. Exposure of pineal glands in organ culture to the calmodulin antagonist R24571 caused a rise in pineal cyclic AMP levels with a concomitant decrease in cAMP-phosphodiesterase activity. This was, however, accompanied by a decline in Nacetyl serotonin and melatonin synthesis. These findings implicate a number of factors in the regulation of pineal NAT activity. A mechanism for the regulation of pineal NAT is proposed.
- Full Text:
- Date Issued: 1993
A polarimetric method for collagenase activity measurement
- Brüning, Adrian Rudolf Nicolaus Ernst
- Authors: Brüning, Adrian Rudolf Nicolaus Ernst
- Date: 1992
- Subjects: Collagenases -- Research , Hides and skins -- Preservation -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4052 , http://hdl.handle.net/10962/d1004113 , Collagenases -- Research , Hides and skins -- Preservation -- Research
- Description: A polarimetric method for monitoring the rate of soluble collagen breakdown by collagenase enzyme action has been developed. The method represents an extension of previous physicochemical techniques based on viscometry, but is simpler and easier to carry out, particularly in the case of reaction rate studies. The method was developed arising from reports of collagenase activity measurement on inappropriate substrates such as gelatin, modified collagens and synthetic polypeptides. The optical method depends on measurement of the loss in optical rotation in solutions of soluble calfskin collagen resulting from initial enzymic cleavage of the collagen trip1e-helix, followed by spontaneous unwinding of the resultant unstable helical fragments. Specific assay conditions were chosen to ensure that the loss in optical rotation following enzymic cleavage was rapid and complete. The method is specific since in the absence of collagenase, non-specific proteinases produce only a limited decrease in solution optical activity. The method has also been compared with established physicochemical assay techniques and compares favourably with both viscometric and titrimetric collagenase assays. The availability of a rapid, sensitive and quantitative procedure for measurement of collagenase activity provides a convenient means for detecting the presence of collagenase in solution and examination of hide bacterial cultures for collagenase production. In addition, a study of biocidal compounds of potential interest in hide preservation for possible inhibitory effects on collagenase is conveniently carried out with the method. Fundamental research into synergistic action in enzymic hydrolysis of collagen is now possible, providing valuable insight into the mechanism of raw hide biodeterioration.
- Full Text:
- Date Issued: 1992
- Authors: Brüning, Adrian Rudolf Nicolaus Ernst
- Date: 1992
- Subjects: Collagenases -- Research , Hides and skins -- Preservation -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4052 , http://hdl.handle.net/10962/d1004113 , Collagenases -- Research , Hides and skins -- Preservation -- Research
- Description: A polarimetric method for monitoring the rate of soluble collagen breakdown by collagenase enzyme action has been developed. The method represents an extension of previous physicochemical techniques based on viscometry, but is simpler and easier to carry out, particularly in the case of reaction rate studies. The method was developed arising from reports of collagenase activity measurement on inappropriate substrates such as gelatin, modified collagens and synthetic polypeptides. The optical method depends on measurement of the loss in optical rotation in solutions of soluble calfskin collagen resulting from initial enzymic cleavage of the collagen trip1e-helix, followed by spontaneous unwinding of the resultant unstable helical fragments. Specific assay conditions were chosen to ensure that the loss in optical rotation following enzymic cleavage was rapid and complete. The method is specific since in the absence of collagenase, non-specific proteinases produce only a limited decrease in solution optical activity. The method has also been compared with established physicochemical assay techniques and compares favourably with both viscometric and titrimetric collagenase assays. The availability of a rapid, sensitive and quantitative procedure for measurement of collagenase activity provides a convenient means for detecting the presence of collagenase in solution and examination of hide bacterial cultures for collagenase production. In addition, a study of biocidal compounds of potential interest in hide preservation for possible inhibitory effects on collagenase is conveniently carried out with the method. Fundamental research into synergistic action in enzymic hydrolysis of collagen is now possible, providing valuable insight into the mechanism of raw hide biodeterioration.
- Full Text:
- Date Issued: 1992
Regulation of the indoleamines by sex steroids
- Authors: Awah, Edmund Kpabi
- Date: 1992
- Subjects: Steroids -- Research , Steroid drugs -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4053 , http://hdl.handle.net/10962/d1004114 , Steroids -- Research , Steroid drugs -- Research
- Description: Alteration of serum tryptophan leads to parallel alterations in brain tryptophan levels. Such changes in brain tryptophan levels has been shown to lead to mood disturbances. The primary enzyme responsible for altering serum tryptophan levels is the liver cytosolic enzyme, tryptophan pyrrolase. Activation of this enzyme is responsible for the enhanced catabolism of circulating tryptophan. The purpose of the present study was firstly to establish whether there is a link between sex steroids and tryptophan pyrrolase activity especially since sex steroids are also known to cause mood disturbances and secondly to determine the effects of sex steroids on brain indolamine metabolism. The results show that all three sex steroids induce the activity of tryptophan pyrrolase implying that they decrease serum tryptophan levels by the activation of tryptophan pyrrolase, thus making less tryptophan available for uptake by the brain. It was also shown that the sex steroids enhance the uptake of ¹⁴C-tryptophan by brain synatopsomes. In addition, the sex steroids influenced the pattern of metabolism of serotonin by organ cultures of rat pineal glands. It is possible that the sex steroids regulate the availability and uptake of indoleamines in the brain.
- Full Text:
- Date Issued: 1992
- Authors: Awah, Edmund Kpabi
- Date: 1992
- Subjects: Steroids -- Research , Steroid drugs -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4053 , http://hdl.handle.net/10962/d1004114 , Steroids -- Research , Steroid drugs -- Research
- Description: Alteration of serum tryptophan leads to parallel alterations in brain tryptophan levels. Such changes in brain tryptophan levels has been shown to lead to mood disturbances. The primary enzyme responsible for altering serum tryptophan levels is the liver cytosolic enzyme, tryptophan pyrrolase. Activation of this enzyme is responsible for the enhanced catabolism of circulating tryptophan. The purpose of the present study was firstly to establish whether there is a link between sex steroids and tryptophan pyrrolase activity especially since sex steroids are also known to cause mood disturbances and secondly to determine the effects of sex steroids on brain indolamine metabolism. The results show that all three sex steroids induce the activity of tryptophan pyrrolase implying that they decrease serum tryptophan levels by the activation of tryptophan pyrrolase, thus making less tryptophan available for uptake by the brain. It was also shown that the sex steroids enhance the uptake of ¹⁴C-tryptophan by brain synatopsomes. In addition, the sex steroids influenced the pattern of metabolism of serotonin by organ cultures of rat pineal glands. It is possible that the sex steroids regulate the availability and uptake of indoleamines in the brain.
- Full Text:
- Date Issued: 1992
The culture of Dunaliella salina and the production of β-carotene in tannery effluents
- Authors: Laubscher, Richard Keith
- Date: 1992
- Subjects: Dunaliella , Carotenes , Tanneries -- Waste disposal , Recycling (Waste, etc.)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4055 , http://hdl.handle.net/10962/d1004116 , Dunaliella , Carotenes , Tanneries -- Waste disposal , Recycling (Waste, etc.)
- Description: The problems of waste disposal in the tanning industry are unique in that the effluents are highly saline, have a high organic loading and contain heavy metals. Methods are available for the safe treatment and disposal of the latter two components, but the saline component requires the expensive outlay of evaporation ponds. This study has identified a possible use for the saline effluents, turning a problematic waste product into a potentially valuable by-product. A range of tannery effluents were identified and tested for their suitability for the mass cultivation of Dunaliella salina (bardawil strain). The bardawil strain was preferred over a local isolate because of its higher production of β-carotene. Ponded tannery effluents and combined processes effluent proved unsuitable for realistic propagation of the alga. Anaerobic digestion of combined processes effluent did not improve its suitability significantly. Anaerobic digestion of hide-soak effluent may remove persistent antimicrobial agents which influence algal growth, but its contribution to enhancing algal growth is equivocal. Undigested hide-soak effluent lacking in persistent antimicrobial agents was found to be an ideal culture medium, as no additional nutrients needed to be added. Significantly higher biomass was obtained in this effluent compared to chemically defined media. Induction of β-carotene was achieved in nitrogen-deficient defined media after culture in tannery effluent. This suggests that a two-stage system using hide-soak effluent for cell propagation and nitrogen deficient media for β-carotene induction, could be possible for the mass cultivation of D. salina for β-carotene production.
- Full Text:
- Date Issued: 1992
- Authors: Laubscher, Richard Keith
- Date: 1992
- Subjects: Dunaliella , Carotenes , Tanneries -- Waste disposal , Recycling (Waste, etc.)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4055 , http://hdl.handle.net/10962/d1004116 , Dunaliella , Carotenes , Tanneries -- Waste disposal , Recycling (Waste, etc.)
- Description: The problems of waste disposal in the tanning industry are unique in that the effluents are highly saline, have a high organic loading and contain heavy metals. Methods are available for the safe treatment and disposal of the latter two components, but the saline component requires the expensive outlay of evaporation ponds. This study has identified a possible use for the saline effluents, turning a problematic waste product into a potentially valuable by-product. A range of tannery effluents were identified and tested for their suitability for the mass cultivation of Dunaliella salina (bardawil strain). The bardawil strain was preferred over a local isolate because of its higher production of β-carotene. Ponded tannery effluents and combined processes effluent proved unsuitable for realistic propagation of the alga. Anaerobic digestion of combined processes effluent did not improve its suitability significantly. Anaerobic digestion of hide-soak effluent may remove persistent antimicrobial agents which influence algal growth, but its contribution to enhancing algal growth is equivocal. Undigested hide-soak effluent lacking in persistent antimicrobial agents was found to be an ideal culture medium, as no additional nutrients needed to be added. Significantly higher biomass was obtained in this effluent compared to chemically defined media. Induction of β-carotene was achieved in nitrogen-deficient defined media after culture in tannery effluent. This suggests that a two-stage system using hide-soak effluent for cell propagation and nitrogen deficient media for β-carotene induction, could be possible for the mass cultivation of D. salina for β-carotene production.
- Full Text:
- Date Issued: 1992
The microbial production of polyphenol oxidase enzyme systems and their application in the treatment of phenolic wastewaters
- Scherman, Patricia Ann (neé Goetch)
- Authors: Scherman, Patricia Ann (neé Goetch)
- Date: 1992
- Subjects: Phenol oxidase Water -- Purification -- Biological treatment Enzymes -- Regulation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4047 , http://hdl.handle.net/10962/d1004108
- Description: Phenolic compounds are a group of organic chemicals present in the wastewaters of many synthetic industrial processes. Due to their extreme toxicity to man and animals, and deleterious impact on the environment, a range of techniques exist for the effective treatment and disposal of these pollutants. Biological degradation using microbial enzymes presents a valuable alternative to conventional wastewater treatment systems. This research was therefore initiated to investigate the polyphenol oxidase enzyme system and the feasibility of its application for effluent treatment and studies in organic solvents. The enzyme system is widely distributed in nature, with Agaricus bisporus (the common mushroom) being the best known producer. Biochemical investigations of the enzyme system were therefore carried out using this extract. A screening programme was initiated to identify microbial polyphenol oxidase producers which could be cultured in liquid media, thereby enabling the production of large quantities of enzyme in fermentation systems. Extensive growth optimization and enzyme induction and optimization studies were carried out on selected cultures. A number of good producers were isolated, namely a bacterial culture designated AECI culture no. 26, Streptomyces antibioticus, Streptomyces glaucescens and a manipulated strain, Streptomyces lividans (pIJ702). Enzyme production by Agaricus bisporus mycelia was optimized in deep-liquid culture; enzyme extracts showed high phenol removal efficiencies. Streptomyces antibioticus, Streptomyces glaucescens, Streptomyces lividans (pIJ702) and AECI culture no. 26 whole cells were also investigated for phenol-removing ability in simulated phenolic effluents. The use of whole cells reduces enzyme inactivation and instability due to the protection of the enzyme system within the cell. All cultures showed improved removal efficiencies in phenolic growth media. These results strongly suggest their use for phenol removal in continuous systems.
- Full Text:
- Date Issued: 1992
- Authors: Scherman, Patricia Ann (neé Goetch)
- Date: 1992
- Subjects: Phenol oxidase Water -- Purification -- Biological treatment Enzymes -- Regulation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4047 , http://hdl.handle.net/10962/d1004108
- Description: Phenolic compounds are a group of organic chemicals present in the wastewaters of many synthetic industrial processes. Due to their extreme toxicity to man and animals, and deleterious impact on the environment, a range of techniques exist for the effective treatment and disposal of these pollutants. Biological degradation using microbial enzymes presents a valuable alternative to conventional wastewater treatment systems. This research was therefore initiated to investigate the polyphenol oxidase enzyme system and the feasibility of its application for effluent treatment and studies in organic solvents. The enzyme system is widely distributed in nature, with Agaricus bisporus (the common mushroom) being the best known producer. Biochemical investigations of the enzyme system were therefore carried out using this extract. A screening programme was initiated to identify microbial polyphenol oxidase producers which could be cultured in liquid media, thereby enabling the production of large quantities of enzyme in fermentation systems. Extensive growth optimization and enzyme induction and optimization studies were carried out on selected cultures. A number of good producers were isolated, namely a bacterial culture designated AECI culture no. 26, Streptomyces antibioticus, Streptomyces glaucescens and a manipulated strain, Streptomyces lividans (pIJ702). Enzyme production by Agaricus bisporus mycelia was optimized in deep-liquid culture; enzyme extracts showed high phenol removal efficiencies. Streptomyces antibioticus, Streptomyces glaucescens, Streptomyces lividans (pIJ702) and AECI culture no. 26 whole cells were also investigated for phenol-removing ability in simulated phenolic effluents. The use of whole cells reduces enzyme inactivation and instability due to the protection of the enzyme system within the cell. All cultures showed improved removal efficiencies in phenolic growth media. These results strongly suggest their use for phenol removal in continuous systems.
- Full Text:
- Date Issued: 1992
Synthesis and interaction of secondary N-nitrosamines with acetylcholinesterase
- Authors: Mmutle, Tsietso Bernard
- Date: 1991
- Subjects: Chemistry, Physical and theoretical , Enzyme kinetics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4058 , http://hdl.handle.net/10962/d1004119 , Chemistry, Physical and theoretical , Enzyme kinetics
- Description: Secondary N-nitrosamines: diphenylnitrosamine (DPhNA), dimethylnitrosamine (DMNA), diethylnitrosamine (DENA), dipropylnitrosamine (DPNA), dibutylnitrosamine (DBNA), diethanolnitrosamine (DEtNA), methylnitrosoglycine (MNGly), nitrosopyrrolidine (NPyr), nitrosomorpholine (NMor) and nitrosopiperidine (NPip) were synthesised and their interaction with acetylcholinesterase (AChE) was investigated. Analyses of kinetic results show that DMNA (Ki=34.78 μM); DENA (Ki=54.24 μM); DPNA(Ki=60.36 μM); DBNA(Ki=95.54 μM); DEtNA(Ki=43.68 μM)MNGly (Ki=30.18 μM); NPip (Ki=123 μM); NPyr (Ki=66.07 μM), NMor (Ki=73.93 μM) and DPhNA (Ki=20.32 μM) are competitive and reversible inhibitors of acetylcholinesterase, with respect to the substrate, acetylthiocholine chloride, ATChCl. With time they act as irreversible covalent inhibitors with dipropy1nitrosamine producing 72% inactivation after 60 minutes. Scatchard analyses of f1uorometric titrations, (Kd=0.75mM-4.09mM); gel chromatography (Kd=O. 80mM-4. 60mM) and equilibrium dia1ysis (Kd=O. 71mM- 4.21mM) for MNG1y, DMNA, DEtNA, DENA, DPNA, NPyr, DSNA, NMor and NPip show that these compounds have weaker affinity for the enzyme, as compared to the much tightly binding aromatic DPhNA, Kd values (0.65mM, 0.68mM and 0.68mM) for fluorometric experiments, gel chromatography and equilibrium dialysis respectively. In all cases, the number of binding sites of acetylcholinesterase averaged to four.
- Full Text:
- Date Issued: 1991
- Authors: Mmutle, Tsietso Bernard
- Date: 1991
- Subjects: Chemistry, Physical and theoretical , Enzyme kinetics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4058 , http://hdl.handle.net/10962/d1004119 , Chemistry, Physical and theoretical , Enzyme kinetics
- Description: Secondary N-nitrosamines: diphenylnitrosamine (DPhNA), dimethylnitrosamine (DMNA), diethylnitrosamine (DENA), dipropylnitrosamine (DPNA), dibutylnitrosamine (DBNA), diethanolnitrosamine (DEtNA), methylnitrosoglycine (MNGly), nitrosopyrrolidine (NPyr), nitrosomorpholine (NMor) and nitrosopiperidine (NPip) were synthesised and their interaction with acetylcholinesterase (AChE) was investigated. Analyses of kinetic results show that DMNA (Ki=34.78 μM); DENA (Ki=54.24 μM); DPNA(Ki=60.36 μM); DBNA(Ki=95.54 μM); DEtNA(Ki=43.68 μM)MNGly (Ki=30.18 μM); NPip (Ki=123 μM); NPyr (Ki=66.07 μM), NMor (Ki=73.93 μM) and DPhNA (Ki=20.32 μM) are competitive and reversible inhibitors of acetylcholinesterase, with respect to the substrate, acetylthiocholine chloride, ATChCl. With time they act as irreversible covalent inhibitors with dipropy1nitrosamine producing 72% inactivation after 60 minutes. Scatchard analyses of f1uorometric titrations, (Kd=0.75mM-4.09mM); gel chromatography (Kd=O. 80mM-4. 60mM) and equilibrium dia1ysis (Kd=O. 71mM- 4.21mM) for MNG1y, DMNA, DEtNA, DENA, DPNA, NPyr, DSNA, NMor and NPip show that these compounds have weaker affinity for the enzyme, as compared to the much tightly binding aromatic DPhNA, Kd values (0.65mM, 0.68mM and 0.68mM) for fluorometric experiments, gel chromatography and equilibrium dialysis respectively. In all cases, the number of binding sites of acetylcholinesterase averaged to four.
- Full Text:
- Date Issued: 1991
Cleavage of the precursor coat protein of black beetle virus strain w17 in rabbit reticulocyte lysate
- Authors: Blackhurst, Diane Mary
- Date: 1988
- Subjects: Beetles , Insects -- Viruses
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3880 , http://hdl.handle.net/10962/d1001614
- Description: Black beetle virus (BBV) is a bipartite single-stranded RNA virus belonging to the family Nodaviridae. Its host range has been found to be limited to insects. RNA 1, the larger of the two RNA molecules, with a MW of 1,15 x 10⁶ and the smaller RNA 2 with a MW of 0,46 x 10⁶, are both packaged in the same virus particle. The two RNA molecules are translated separately, with RNA 1 coding for protein A of MW 105 x 10³ and RNA 2 coding for protein α of MW 47 x 10³. Protein α is the major capsid protein precursor, which during in vivo maturation is cleaved to form the coat protein β of MW 43 x 10³, and protein γ of MW 5 x 10³. Cell-free translation of BBV (strain W17) mRNA was carried out in rabbit reticulocyte lysates. Protein α was detectable between 0 and 30 minutes after RNA addition. A protein 'β', which was found to co-electrophorese on polyacrylamide gels with authentic β and which was immunoprecipitated by anti-BBV antiserum, was detectable after 30 minutes. Results of this work show that the formation of 'β' could be prevented by the addition of RNase to the lysate, indicating that intact RNA is necessary for α to β cleavage. Arresting protein synthesis by the addition of cycloheximide to the lysate mix did not inhibit the cleavage. The formation of β could also be prevented by cooling the lysate mix to 1°C. Cleavage of α to β still occurred when RNA 2, without the presence of RNA 1, was translated. Therefore the cleavage is not dependent on a translation product of RNA 1. Sedimentation of lysate on sucrose density gradients showed that α to β cleavage was not accompanied by assembly of BBV RNA and protein lnto a viral substructure as has been shown to occur with some viruses, for example certain picornaviruses. Serial dilution of lysate containing α showed that the level of β decreased with increasing dilution, indicating that the cleavage is not mediated by autocatalysis, but by some other unknown factor. Although much work has been carried out on black beetle virus, no work has been published to date concerning α to β cleavage as an indication of assembly in rabbit reticulocyte lysates. Results of these cell-free translation experiments thus indicate that BBV coat protein precursor α, in association with its messenger RNA 2, undergoes a maturation cleavage in the lysate to produce BBV coat protein β. In addition, this cleavage seems to occur without assembly into any intermediate viral structure
- Full Text:
- Date Issued: 1988
- Authors: Blackhurst, Diane Mary
- Date: 1988
- Subjects: Beetles , Insects -- Viruses
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3880 , http://hdl.handle.net/10962/d1001614
- Description: Black beetle virus (BBV) is a bipartite single-stranded RNA virus belonging to the family Nodaviridae. Its host range has been found to be limited to insects. RNA 1, the larger of the two RNA molecules, with a MW of 1,15 x 10⁶ and the smaller RNA 2 with a MW of 0,46 x 10⁶, are both packaged in the same virus particle. The two RNA molecules are translated separately, with RNA 1 coding for protein A of MW 105 x 10³ and RNA 2 coding for protein α of MW 47 x 10³. Protein α is the major capsid protein precursor, which during in vivo maturation is cleaved to form the coat protein β of MW 43 x 10³, and protein γ of MW 5 x 10³. Cell-free translation of BBV (strain W17) mRNA was carried out in rabbit reticulocyte lysates. Protein α was detectable between 0 and 30 minutes after RNA addition. A protein 'β', which was found to co-electrophorese on polyacrylamide gels with authentic β and which was immunoprecipitated by anti-BBV antiserum, was detectable after 30 minutes. Results of this work show that the formation of 'β' could be prevented by the addition of RNase to the lysate, indicating that intact RNA is necessary for α to β cleavage. Arresting protein synthesis by the addition of cycloheximide to the lysate mix did not inhibit the cleavage. The formation of β could also be prevented by cooling the lysate mix to 1°C. Cleavage of α to β still occurred when RNA 2, without the presence of RNA 1, was translated. Therefore the cleavage is not dependent on a translation product of RNA 1. Sedimentation of lysate on sucrose density gradients showed that α to β cleavage was not accompanied by assembly of BBV RNA and protein lnto a viral substructure as has been shown to occur with some viruses, for example certain picornaviruses. Serial dilution of lysate containing α showed that the level of β decreased with increasing dilution, indicating that the cleavage is not mediated by autocatalysis, but by some other unknown factor. Although much work has been carried out on black beetle virus, no work has been published to date concerning α to β cleavage as an indication of assembly in rabbit reticulocyte lysates. Results of these cell-free translation experiments thus indicate that BBV coat protein precursor α, in association with its messenger RNA 2, undergoes a maturation cleavage in the lysate to produce BBV coat protein β. In addition, this cleavage seems to occur without assembly into any intermediate viral structure
- Full Text:
- Date Issued: 1988
Polymerized serum albumin beads for use as slow-release adjuvants
- Martin, Michelle Elizabeth Denny
- Authors: Martin, Michelle Elizabeth Denny
- Date: 1988
- Subjects: Serum albumin , Antigens , Vaccines
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3879 , http://hdl.handle.net/10962/d1001613
- Description: Experimental vaccines have been made by covalently bonding virus particles into polymerized rabbit serum albumin beads. Using Nodamura virus as a model antigen, these model vaccines induced specific humoral antibody production, comparable with that achieved using Freund's adjuvants. Virus specific antibodies were also induced when Nodamura virus was covalently attached to the bead surface using different crosslinkers. However, when poliovirus type 2 (Sabin strain) was polymerized into beads, the levels of neutralizing antibodies were insignificant compared with control aqueous vaccines. The synthetic immunostimulator, muramyl dipeptide, was included with bead vaccines in an attempt to potentiate the immune response. Immunostimulation is achieved by a slow release of antigen coinciding with the gradual breakdown of bead structure.
- Full Text:
- Date Issued: 1988
- Authors: Martin, Michelle Elizabeth Denny
- Date: 1988
- Subjects: Serum albumin , Antigens , Vaccines
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3879 , http://hdl.handle.net/10962/d1001613
- Description: Experimental vaccines have been made by covalently bonding virus particles into polymerized rabbit serum albumin beads. Using Nodamura virus as a model antigen, these model vaccines induced specific humoral antibody production, comparable with that achieved using Freund's adjuvants. Virus specific antibodies were also induced when Nodamura virus was covalently attached to the bead surface using different crosslinkers. However, when poliovirus type 2 (Sabin strain) was polymerized into beads, the levels of neutralizing antibodies were insignificant compared with control aqueous vaccines. The synthetic immunostimulator, muramyl dipeptide, was included with bead vaccines in an attempt to potentiate the immune response. Immunostimulation is achieved by a slow release of antigen coinciding with the gradual breakdown of bead structure.
- Full Text:
- Date Issued: 1988
Studies on the gastric proteases in three South African snake species
- Robertson, Sirion Sholto Douglas
- Authors: Robertson, Sirion Sholto Douglas
- Date: 1987
- Subjects: Snakes -- South Africa Proteolytic enzymes Pepsin Pepsinogen
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4063 , http://hdl.handle.net/10962/d1004639
- Description: The pepsinogens and pepsins of cobra, mole snake and puff adder have been studied. The pepsinogens of all three species fall into two distinct groups, here designated PI and PII. At least the latter group, in all cases, shows substantial microheterogeneity. Physicochemical studies suggest that the cobra and puff adder PII groups are more similar to each other than either is to the mole snake PII group. Kinetic studies indicate that, in the cobra and mole snake, the PI and PII pepsins differ in their Arrhenius activation energies. Such difference is smaller, or absent, in the case of the puff adder PI and PII pepsins. These characteristics of the pepsins are assessed in the context of the differences between the oral secretions of the three species studied. The suggestion is advanced that the puff adder's strongly proteolytic venom has influenced certain properties of its gastric proteases.
- Full Text:
- Date Issued: 1987
- Authors: Robertson, Sirion Sholto Douglas
- Date: 1987
- Subjects: Snakes -- South Africa Proteolytic enzymes Pepsin Pepsinogen
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4063 , http://hdl.handle.net/10962/d1004639
- Description: The pepsinogens and pepsins of cobra, mole snake and puff adder have been studied. The pepsinogens of all three species fall into two distinct groups, here designated PI and PII. At least the latter group, in all cases, shows substantial microheterogeneity. Physicochemical studies suggest that the cobra and puff adder PII groups are more similar to each other than either is to the mole snake PII group. Kinetic studies indicate that, in the cobra and mole snake, the PI and PII pepsins differ in their Arrhenius activation energies. Such difference is smaller, or absent, in the case of the puff adder PI and PII pepsins. These characteristics of the pepsins are assessed in the context of the differences between the oral secretions of the three species studied. The suggestion is advanced that the puff adder's strongly proteolytic venom has influenced certain properties of its gastric proteases.
- Full Text:
- Date Issued: 1987
A study of petrol and diesel fuel blends with special reference to their thermodynamic propeties and phase equilibria
- Authors: Hayward, Caroline
- Date: 1986
- Subjects: Gasoline , Diesel fuels , Thermodynamics , Liquid-liquid equilibrium , Alcohol as fuel
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4065 , http://hdl.handle.net/10962/d1004902 , Gasoline , Diesel fuels , Thermodynamics , Liquid-liquid equilibrium , Alcohol as fuel
- Description: The ternary phase behaviour of the n-heptane-l-propanol-water system was studied and compared with the theoretical prediction based on the UNIQUAC model for non-electrolyte solutions. The results showed that this model adequately approximated experimental studies. The excess enthalpies and excess volumes for several binary mixtures were determined. The excess enthalpies were measured using a LKB flow microcalorimeter and the excess -volumes determined using a PAAR densitometer. The study showed that no significant enthalpy or volume changes occurred when petrol/n-heptane were mixed with alcohols . Ternary phase diagrams, including tie lines have been determined for a number of petrol-alcohol-water systems (including the Sasol blend of alcohols). The tie line results show that the concentration of water in the water-rich layer is strongly dependent on the type of alcohol used. The Sasol alcohol blended with petrol resulted in a high water concentration in the water-rich layer which forms on phase separation. This is believed to contribute significantly to the corrosion problems experienced by motorists using the Sasol blended fuel on the Witwatersrand. The effect of temperature on several of these blends was included in the study. Diesel-alcohol blends and the co-solvent properties of ethyl acetate investigated. Ethyl acetate ensures miscibility at low concentrations for diesel-ethanol blends. Octyl nitrate and two cetane improvers from AECI were assessed in terms of their ability to restore cetane rating of blended diesel fuel to that of pure diesel fuel. The results indicated that all three samples were successful in this application. , KMBT_363
- Full Text:
- Date Issued: 1986
- Authors: Hayward, Caroline
- Date: 1986
- Subjects: Gasoline , Diesel fuels , Thermodynamics , Liquid-liquid equilibrium , Alcohol as fuel
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4065 , http://hdl.handle.net/10962/d1004902 , Gasoline , Diesel fuels , Thermodynamics , Liquid-liquid equilibrium , Alcohol as fuel
- Description: The ternary phase behaviour of the n-heptane-l-propanol-water system was studied and compared with the theoretical prediction based on the UNIQUAC model for non-electrolyte solutions. The results showed that this model adequately approximated experimental studies. The excess enthalpies and excess volumes for several binary mixtures were determined. The excess enthalpies were measured using a LKB flow microcalorimeter and the excess -volumes determined using a PAAR densitometer. The study showed that no significant enthalpy or volume changes occurred when petrol/n-heptane were mixed with alcohols . Ternary phase diagrams, including tie lines have been determined for a number of petrol-alcohol-water systems (including the Sasol blend of alcohols). The tie line results show that the concentration of water in the water-rich layer is strongly dependent on the type of alcohol used. The Sasol alcohol blended with petrol resulted in a high water concentration in the water-rich layer which forms on phase separation. This is believed to contribute significantly to the corrosion problems experienced by motorists using the Sasol blended fuel on the Witwatersrand. The effect of temperature on several of these blends was included in the study. Diesel-alcohol blends and the co-solvent properties of ethyl acetate investigated. Ethyl acetate ensures miscibility at low concentrations for diesel-ethanol blends. Octyl nitrate and two cetane improvers from AECI were assessed in terms of their ability to restore cetane rating of blended diesel fuel to that of pure diesel fuel. The results indicated that all three samples were successful in this application. , KMBT_363
- Full Text:
- Date Issued: 1986
A novel adjuvant : polymerised serum albumin beads
- Authors: Dewar, John Barr
- Date: 1985
- Subjects: Antigens , Serum albumin
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4104 , http://hdl.handle.net/10962/d1011146 , Antigens , Serum albumin
- Description: Lee, T. et al (1981) proposed the encapsulation of hormones such as progesterone into serum albumin beads, such that their in vivo proteolysis would allow a gradual release of hormone at low levels, for extended hormone action. It was proposed, in the Department of Microbiology, Rhodes University, to replace the hormone component of the above bead formulation, with virus as antigen, in the development of a vaccine. Beads optimally crosslinked at 1% final glutaraldehyde concentration, containing Nodamura virus, were shown to promote an adjuvant effect in vivo, analogous to the release of antigen from Freund's Complete Adjuvant (FCA), so that extended immunostimulation resulted. It was shown that soluble antigen promoted a short-lived primary immune response, peaking around day 25 following inoculation. Antigen presented in beads, on the other hand, initially elicited a low humoral response, but this response gradually increased up to a peak around day 110 post inoculation, before decreasing. No apparent adverse side-effects were noted following inoculation of antigen-containing serum albumin beads, compared to necrosis following antigen in FCA inoculation, supporting the proposal of using albumin homotypic for the test inoculee animal, so that the beads would themselves be non-immunogenic and would merely act as a vehicle in the vaccine formulation. The indirect enzyme-linked immunosorbent assay (ELISA) was used to monitor the humoral response to antigen following inoculation. Results showed that covalent crosslinking of albumin in the formation of the beads did not promote immunogenicity on the part of the chemically altered albumin. The ELISA test was used to indicate the kinetics of the IgG response to Nodamura virus when presented in formulations such as: Freely soluble virus or its subunit; soluble intact virus inactivated by treatment with glutaraldehyde; intact virus entrapped in serum albumin beads cross; linked at different percentage final glutaraldehyde concentrations and also virus subunit prepared in albumin beads. The presence of virus-neutral ising antibodies was noted in serum obtained from rabbits inoculated with virus entrapped in albumin beads. Virus infectivity, titrated in mice, showed protection against virus challenge after incubation of virus with serum obtained above.
- Full Text:
- Date Issued: 1985
- Authors: Dewar, John Barr
- Date: 1985
- Subjects: Antigens , Serum albumin
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4104 , http://hdl.handle.net/10962/d1011146 , Antigens , Serum albumin
- Description: Lee, T. et al (1981) proposed the encapsulation of hormones such as progesterone into serum albumin beads, such that their in vivo proteolysis would allow a gradual release of hormone at low levels, for extended hormone action. It was proposed, in the Department of Microbiology, Rhodes University, to replace the hormone component of the above bead formulation, with virus as antigen, in the development of a vaccine. Beads optimally crosslinked at 1% final glutaraldehyde concentration, containing Nodamura virus, were shown to promote an adjuvant effect in vivo, analogous to the release of antigen from Freund's Complete Adjuvant (FCA), so that extended immunostimulation resulted. It was shown that soluble antigen promoted a short-lived primary immune response, peaking around day 25 following inoculation. Antigen presented in beads, on the other hand, initially elicited a low humoral response, but this response gradually increased up to a peak around day 110 post inoculation, before decreasing. No apparent adverse side-effects were noted following inoculation of antigen-containing serum albumin beads, compared to necrosis following antigen in FCA inoculation, supporting the proposal of using albumin homotypic for the test inoculee animal, so that the beads would themselves be non-immunogenic and would merely act as a vehicle in the vaccine formulation. The indirect enzyme-linked immunosorbent assay (ELISA) was used to monitor the humoral response to antigen following inoculation. Results showed that covalent crosslinking of albumin in the formation of the beads did not promote immunogenicity on the part of the chemically altered albumin. The ELISA test was used to indicate the kinetics of the IgG response to Nodamura virus when presented in formulations such as: Freely soluble virus or its subunit; soluble intact virus inactivated by treatment with glutaraldehyde; intact virus entrapped in serum albumin beads cross; linked at different percentage final glutaraldehyde concentrations and also virus subunit prepared in albumin beads. The presence of virus-neutral ising antibodies was noted in serum obtained from rabbits inoculated with virus entrapped in albumin beads. Virus infectivity, titrated in mice, showed protection against virus challenge after incubation of virus with serum obtained above.
- Full Text:
- Date Issued: 1985
A study of the molecular variation between orbivirus proteins
- Authors: Whistler, Toni
- Date: 1985 , 2013-03-13
- Subjects: Proteins -- Analysis , Polypeptides , Bluetongue virus , Orbivirus infections
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3892 , http://hdl.handle.net/10962/d1003290 , Proteins -- Analysis , Polypeptides , Bluetongue virus , Orbivirus infections
- Description: The aim of this study was to initiate a structural analysis of the capsid polypeptides from several serotypes of bluetongue virus in order to provide insight into the relatedness and possible origins of the different serotypes. Tryptic peptide mapping of ¹²⁵I-labelled group antigen by ion exchange chromatography was used to assess the structural relatedness of seven BTV serotypes from Southern Africa, North America and Australia. Each serotype had several tyrosine containing tryptic peptides which were unique, but approximately 35% of the peptides analyzed were found to be highly conserved between all 7 serotypes. BTV-20 appeared to be closely related to BTV-B and these two serotypes with BTV-4 and BTV-17 appeared to form a closely knit central cluster. , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 1985
- Authors: Whistler, Toni
- Date: 1985 , 2013-03-13
- Subjects: Proteins -- Analysis , Polypeptides , Bluetongue virus , Orbivirus infections
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3892 , http://hdl.handle.net/10962/d1003290 , Proteins -- Analysis , Polypeptides , Bluetongue virus , Orbivirus infections
- Description: The aim of this study was to initiate a structural analysis of the capsid polypeptides from several serotypes of bluetongue virus in order to provide insight into the relatedness and possible origins of the different serotypes. Tryptic peptide mapping of ¹²⁵I-labelled group antigen by ion exchange chromatography was used to assess the structural relatedness of seven BTV serotypes from Southern Africa, North America and Australia. Each serotype had several tyrosine containing tryptic peptides which were unique, but approximately 35% of the peptides analyzed were found to be highly conserved between all 7 serotypes. BTV-20 appeared to be closely related to BTV-B and these two serotypes with BTV-4 and BTV-17 appeared to form a closely knit central cluster. , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 1985
Characterization and mode of action of a bacteriocin produced by a Bacteroides Fragilis strain
- Mossie, Godwin Mxolisi Kevin
- Authors: Mossie, Godwin Mxolisi Kevin
- Date: 1980
- Subjects: Bacteroides , Anaerobic bacteria , Trypsin , Dinitrophenol , Proteins -- Synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4124 , http://hdl.handle.net/10962/d1013543
- Description: Bacteroides fragilis strain Bf-1 produces an extracellular bacteriocin at the beginning of the stationary growth phase. Production is not inducible by either ultraviolet light or mitomycin C. The low molecular weight bacteriocin (MW estimates of 13 500 and 18 800 obtained from Sephadex G-100 chromatography and SDS-PAGE electrophoresis respecively) is stable between pH 7 - 9 and is inactivated on incubation with trypsin and pronase. An unusual feature of the Bf-1 bacteriocin is its apparent biphasic temperature stability: while the majority of the activity (97%) is destroyed by heating at 60ºC (t [subscript] 1/2 = 2.5 min at 60ºC), a small proportion (3%) is stable even after autoclaving at 121ºC for 15 min. The killing of sensitive cells occurs in 2 stages and the killing action is reversed by incubation with trypsin. The transition from stage I to stage II is dependent on the temperature of incubation and the growth state of sensitive cells. 2,4-Dinitrophenol prevents this transition. The Bf-1 bacteriocin has an unusual mode of action. It specifically inhibits RNA synthesis whilst having no effect on protein or DNA synthesis. No effect on intracellular ATP levels were observed. The heat-stable (3%) fraction had a similar biochemical effect. In vitro studies involving RNA polymerase indicated that the bacteriocin and the antibiotic rifampicin have similar effects on RNA synthesis. The bacteriocinogenic strain (Bf-1) is insensitive to its own bacteriocin both in vivo and in vitro, although this immunity is overcome in vitro by the addition of higher concentrations of the Bf-1 bacteriocin. The bacteriocinogenic strain (Bf-1) harbors a cryptic plasmid (or plasmids) which on a neutral sucrose gradient, sediments faster than the Col E1 marker plasmid DNA. Attempts to cure this strain of its bacteriocinogenic phenotype were unsuccessful.
- Full Text:
- Date Issued: 1980
- Authors: Mossie, Godwin Mxolisi Kevin
- Date: 1980
- Subjects: Bacteroides , Anaerobic bacteria , Trypsin , Dinitrophenol , Proteins -- Synthesis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4124 , http://hdl.handle.net/10962/d1013543
- Description: Bacteroides fragilis strain Bf-1 produces an extracellular bacteriocin at the beginning of the stationary growth phase. Production is not inducible by either ultraviolet light or mitomycin C. The low molecular weight bacteriocin (MW estimates of 13 500 and 18 800 obtained from Sephadex G-100 chromatography and SDS-PAGE electrophoresis respecively) is stable between pH 7 - 9 and is inactivated on incubation with trypsin and pronase. An unusual feature of the Bf-1 bacteriocin is its apparent biphasic temperature stability: while the majority of the activity (97%) is destroyed by heating at 60ºC (t [subscript] 1/2 = 2.5 min at 60ºC), a small proportion (3%) is stable even after autoclaving at 121ºC for 15 min. The killing of sensitive cells occurs in 2 stages and the killing action is reversed by incubation with trypsin. The transition from stage I to stage II is dependent on the temperature of incubation and the growth state of sensitive cells. 2,4-Dinitrophenol prevents this transition. The Bf-1 bacteriocin has an unusual mode of action. It specifically inhibits RNA synthesis whilst having no effect on protein or DNA synthesis. No effect on intracellular ATP levels were observed. The heat-stable (3%) fraction had a similar biochemical effect. In vitro studies involving RNA polymerase indicated that the bacteriocin and the antibiotic rifampicin have similar effects on RNA synthesis. The bacteriocinogenic strain (Bf-1) is insensitive to its own bacteriocin both in vivo and in vitro, although this immunity is overcome in vitro by the addition of higher concentrations of the Bf-1 bacteriocin. The bacteriocinogenic strain (Bf-1) harbors a cryptic plasmid (or plasmids) which on a neutral sucrose gradient, sediments faster than the Col E1 marker plasmid DNA. Attempts to cure this strain of its bacteriocinogenic phenotype were unsuccessful.
- Full Text:
- Date Issued: 1980
Bacterial degradation of ixodicide amitraz
- Authors: Allcock, Errol Ralph
- Date: 1978
- Subjects: Ticks -- Control , Pesticides -- Biodegradation , Acaricides
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4081 , http://hdl.handle.net/10962/d1007473 , Ticks -- Control , Pesticides -- Biodegradation , Acaricides
- Description: The control of ticks on cattle has long been a matter of prime importance to stock owners over most of the intensive natural grazing areas in the Southern Hemisphere. The only practical method of dealing with the cattle tick problem in the short term is by treating the infected bovine host with ixodicides i. e. by chemical control. This can be achieved by either plunging the cattle into a dip tank containing aqueous suspensions or emulsions of the ixodicide or by spraying them with dip suspensions in a spray race.
- Full Text:
- Date Issued: 1978
- Authors: Allcock, Errol Ralph
- Date: 1978
- Subjects: Ticks -- Control , Pesticides -- Biodegradation , Acaricides
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4081 , http://hdl.handle.net/10962/d1007473 , Ticks -- Control , Pesticides -- Biodegradation , Acaricides
- Description: The control of ticks on cattle has long been a matter of prime importance to stock owners over most of the intensive natural grazing areas in the Southern Hemisphere. The only practical method of dealing with the cattle tick problem in the short term is by treating the infected bovine host with ixodicides i. e. by chemical control. This can be achieved by either plunging the cattle into a dip tank containing aqueous suspensions or emulsions of the ixodicide or by spraying them with dip suspensions in a spray race.
- Full Text:
- Date Issued: 1978
Genetic and bacteriophage studies on Bacteroides thetaiotaomicron and related anaerobic strains
- Authors: Burt, Sharon Joy
- Date: 1978
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:20972 , http://hdl.handle.net/10962/5753
- Description: Gram-negative obligately anaerobic bacilli were isolated from faeces on selective media. R plasmid transfer was investigated in mating experiments between 30 anaerobes and between the anaerobes and known donor and recipient E. coli strains. The transfer of R plasmids from E.coli to B.fragilis, Bacteroides spp., Fusobacterium spp. and other faecal obligate anaerobic bacteria was possible after heat treatment of the recipients at 50°C. The anaerobic exconjugants were unstable and were not able to retransfer the ampr marker. A bacteriophage, B1 , specific for the anaerobe B.thetaiotaomicron, was isolated and characterised. The properties of the phage included a variable burst size and the production of many defective phage particles without tails which were not viable. The B.thetaiotaomicron host was able to establish a phage carrier state with B1 phage. Phenol-extracted phage DNA could transfect ca2+-treated B.thetaiotaomicron cells and transfection was not limited to a particular stage in the growth cycle. An obligatory step in the transfection procedure was a 33-fold dilution in broth, allowing replication of the infected cells. Prolonged incubation of treated cells with DNA prior to dilution in broth resulted in a large decrease in phage titre. The application of this transfection system to the development of a transformation system was not successful . Conventional transformation procedures did not yield transformants, and it was not possible to transduce B.thetaiotaomicron with B1 phage. The B.thetaiotaomicron strain used was distinguished by the formation of two distinct morphological variants. Each morphological type gave rise to the other at the same frequency. Environmental conditions other than elevated temperature, had no effect on the segregation frequency. The grey colony variant was not capsulated and was sensitive to B1 phage, whereas the white colony type was encapsulated and was phage-resistant. Another feature of the B.thetaiotaomicron strain was the low incidence of mutants. A second survey of the occurrence of R plasmids in aerobic coliforms from a remote area of the Transkei and from an urban area, was undertaken. An increase in transferable antibiotic resistance was found over the last three years. It can be concluded that this was a result of the use of antibiotics among the human population, since there are no veterinary services in the area and the addition of antibiotics to animal feeds is not practised.
- Full Text:
- Date Issued: 1978
- Authors: Burt, Sharon Joy
- Date: 1978
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:20972 , http://hdl.handle.net/10962/5753
- Description: Gram-negative obligately anaerobic bacilli were isolated from faeces on selective media. R plasmid transfer was investigated in mating experiments between 30 anaerobes and between the anaerobes and known donor and recipient E. coli strains. The transfer of R plasmids from E.coli to B.fragilis, Bacteroides spp., Fusobacterium spp. and other faecal obligate anaerobic bacteria was possible after heat treatment of the recipients at 50°C. The anaerobic exconjugants were unstable and were not able to retransfer the ampr marker. A bacteriophage, B1 , specific for the anaerobe B.thetaiotaomicron, was isolated and characterised. The properties of the phage included a variable burst size and the production of many defective phage particles without tails which were not viable. The B.thetaiotaomicron host was able to establish a phage carrier state with B1 phage. Phenol-extracted phage DNA could transfect ca2+-treated B.thetaiotaomicron cells and transfection was not limited to a particular stage in the growth cycle. An obligatory step in the transfection procedure was a 33-fold dilution in broth, allowing replication of the infected cells. Prolonged incubation of treated cells with DNA prior to dilution in broth resulted in a large decrease in phage titre. The application of this transfection system to the development of a transformation system was not successful . Conventional transformation procedures did not yield transformants, and it was not possible to transduce B.thetaiotaomicron with B1 phage. The B.thetaiotaomicron strain used was distinguished by the formation of two distinct morphological variants. Each morphological type gave rise to the other at the same frequency. Environmental conditions other than elevated temperature, had no effect on the segregation frequency. The grey colony variant was not capsulated and was sensitive to B1 phage, whereas the white colony type was encapsulated and was phage-resistant. Another feature of the B.thetaiotaomicron strain was the low incidence of mutants. A second survey of the occurrence of R plasmids in aerobic coliforms from a remote area of the Transkei and from an urban area, was undertaken. An increase in transferable antibiotic resistance was found over the last three years. It can be concluded that this was a result of the use of antibiotics among the human population, since there are no veterinary services in the area and the addition of antibiotics to animal feeds is not practised.
- Full Text:
- Date Issued: 1978
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
- 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
Bacterial degradation of the acaricide amitraz
- Authors: Baker, Penelope Bridget
- Date: 1976
- Subjects: Acaricides , Biodegradation , Gas chromatography , Bacteriology -- Cultures and culture media
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4099 , http://hdl.handle.net/10962/d1009498
- Description: This thesis describes dip tank field trials and laboratory investigations on the acaricide Amitraz. Amitraz is a triazapenta- diene compound which is relatively unstable in fouled dip washes. The field trials were conducted on the farm Sea View according to the "Total Replacement Method" and on the farm Sea Ways according to the "Lime Stabilization Method" of dipping. The results of these trials showed that Amitraz was stable in clean dip washes, and under conditions of high pH resulting from the addition of slaked lime to the dip wash. Using mixed bacterial populations optimum conditions for degradation of Amitraz in the laboratory were determined. Bacterial cultures degraded Amitraz most efficiently in media supplemented with yeast extract or with a high content of sterile cattle faeces. Amitraz concentrations were determined by gas chromatography. A culture. efficient at degrading Amitraz was enriched from a dip tank sludge inoculum. From this culture ten bacterial isolates were identified; nine of these were of the genus Pseudomonas and one was an Achromobacter sp. Experiments with both mixed and pure cultures demonstrated that bacterial degradation of Amitraz was by the process of co-metabolism. The existence of four degradation products was shown using thin layer chromatography. Tentative identification of two of the products was made.
- Full Text:
- Date Issued: 1976
- Authors: Baker, Penelope Bridget
- Date: 1976
- Subjects: Acaricides , Biodegradation , Gas chromatography , Bacteriology -- Cultures and culture media
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4099 , http://hdl.handle.net/10962/d1009498
- Description: This thesis describes dip tank field trials and laboratory investigations on the acaricide Amitraz. Amitraz is a triazapenta- diene compound which is relatively unstable in fouled dip washes. The field trials were conducted on the farm Sea View according to the "Total Replacement Method" and on the farm Sea Ways according to the "Lime Stabilization Method" of dipping. The results of these trials showed that Amitraz was stable in clean dip washes, and under conditions of high pH resulting from the addition of slaked lime to the dip wash. Using mixed bacterial populations optimum conditions for degradation of Amitraz in the laboratory were determined. Bacterial cultures degraded Amitraz most efficiently in media supplemented with yeast extract or with a high content of sterile cattle faeces. Amitraz concentrations were determined by gas chromatography. A culture. efficient at degrading Amitraz was enriched from a dip tank sludge inoculum. From this culture ten bacterial isolates were identified; nine of these were of the genus Pseudomonas and one was an Achromobacter sp. Experiments with both mixed and pure cultures demonstrated that bacterial degradation of Amitraz was by the process of co-metabolism. The existence of four degradation products was shown using thin layer chromatography. Tentative identification of two of the products was made.
- Full Text:
- Date Issued: 1976