Use of flow reactors for an improved synthesis of Tenofovir derivatives
- Authors: Sonti, Thembela
- Date: 2023-04
- Subjects: Antiviral agents -- South Africa , HIV infections –Treatment
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/61190 , vital:69792
- Description: Tenofovir disoproxil fumarate (TDF) is a prescription drug used to treat and prevent human immunodeficiency virus (HIV) infections. It aids in the reduction of HIV in the body, allowing the immune system to function more effectively. This reduces the risk of HIV complications, such as infections, whilst improving the quality of life. TDF belongs to the nucleotide reverse transcriptase inhibitors category of drugs. These drugs limit the ability of the reverse transcriptase, an enzyme essential for each virus to replicate itself. A reduction in the cost of HIV treatment could improve supply security and make it more accessible to patients in need. Thus, this project aims to use flow technology to achieve a guaranteed supply chain and access. In this thesis, a method for the synthesis of TDF was developed using microreactors starting from the readily available adenine. The method was adapted from the traditional batch synthesis as currently there is no literature on the synthesis of TDF in flow chemistry. The batch methods used for the synthesis of the working standards were successfully translated to flow systems. For the best results to be obtained, optimisation of the reaction temperature, reagent molar equivalents and concentration was critical. From the optimisation studies, an improvement in conversion is evident throughout all stages. The flow synthesis of the first intermediate resulted in a conversion of 100 % in N,N-dimethylformamide in 6 min residence time. This study was conducted at 200 °C, which is higher than the boiling point of the solvent with the aid of a back pressure regulator. A key reagent in the synthesis of tenofovir, namely ((tosyloxy)methyl)phosphonic acid, had to be synthesised and it was successfully produced in 96 % yield. The second intermediate was synthesised through a successful coupling reaction between (R)-9-(2-hydroxypropyl)adenine and ((tosyloxy)methyl)- phosphonic acid, which afforded a 100 % conversion of tenofovir in 20 min total residence time. The multistep synthesis of tenofovir was a success as it afforded a 65 % overall conversion. The prodrug TDF was successfully synthesised at 120 °C with a 30 min residence time, yielding a conversion of 100 %. ii | P a g e This thesis consists of four chapters. Chapter one describes the background on HIV and a literature review on HIV drugs. This chapter also demonstrates flow chemistry and microreactors in detail and different routes for the synthesis of TDF in traditional batch methods. Chapter two provides a detailed methodology for batch synthesis and flow synthesis with analytical data. 1H-NMR, 13C-NMR and FTIR spectroscopy was used to evaluate all the compounds synthesised in this chapter. Chapter three thoroughly discusses the results that were obtained graphically, showing that the flow synthesis gives better yields than batch synthesis. In chapter 4, the conclusion of the whole investigation is stated along with the future work for the preparation of TDF. , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Sonti, Thembela
- Date: 2023-04
- Subjects: Antiviral agents -- South Africa , HIV infections –Treatment
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/61190 , vital:69792
- Description: Tenofovir disoproxil fumarate (TDF) is a prescription drug used to treat and prevent human immunodeficiency virus (HIV) infections. It aids in the reduction of HIV in the body, allowing the immune system to function more effectively. This reduces the risk of HIV complications, such as infections, whilst improving the quality of life. TDF belongs to the nucleotide reverse transcriptase inhibitors category of drugs. These drugs limit the ability of the reverse transcriptase, an enzyme essential for each virus to replicate itself. A reduction in the cost of HIV treatment could improve supply security and make it more accessible to patients in need. Thus, this project aims to use flow technology to achieve a guaranteed supply chain and access. In this thesis, a method for the synthesis of TDF was developed using microreactors starting from the readily available adenine. The method was adapted from the traditional batch synthesis as currently there is no literature on the synthesis of TDF in flow chemistry. The batch methods used for the synthesis of the working standards were successfully translated to flow systems. For the best results to be obtained, optimisation of the reaction temperature, reagent molar equivalents and concentration was critical. From the optimisation studies, an improvement in conversion is evident throughout all stages. The flow synthesis of the first intermediate resulted in a conversion of 100 % in N,N-dimethylformamide in 6 min residence time. This study was conducted at 200 °C, which is higher than the boiling point of the solvent with the aid of a back pressure regulator. A key reagent in the synthesis of tenofovir, namely ((tosyloxy)methyl)phosphonic acid, had to be synthesised and it was successfully produced in 96 % yield. The second intermediate was synthesised through a successful coupling reaction between (R)-9-(2-hydroxypropyl)adenine and ((tosyloxy)methyl)- phosphonic acid, which afforded a 100 % conversion of tenofovir in 20 min total residence time. The multistep synthesis of tenofovir was a success as it afforded a 65 % overall conversion. The prodrug TDF was successfully synthesised at 120 °C with a 30 min residence time, yielding a conversion of 100 %. ii | P a g e This thesis consists of four chapters. Chapter one describes the background on HIV and a literature review on HIV drugs. This chapter also demonstrates flow chemistry and microreactors in detail and different routes for the synthesis of TDF in traditional batch methods. Chapter two provides a detailed methodology for batch synthesis and flow synthesis with analytical data. 1H-NMR, 13C-NMR and FTIR spectroscopy was used to evaluate all the compounds synthesised in this chapter. Chapter three thoroughly discusses the results that were obtained graphically, showing that the flow synthesis gives better yields than batch synthesis. In chapter 4, the conclusion of the whole investigation is stated along with the future work for the preparation of TDF. , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Exploring how Grade 11 chemistry teachers make use of the periodic table of elements when mediating learning of writing and balancing chemical equations
- Kambeyo, Reginald Ndeshipanda
- Authors: Kambeyo, Reginald Ndeshipanda
- Date: 2021-10-29
- Subjects: Chemistry Study and teaching (Secondary) Namibia , Periodic table of the elements , Chemical equations Study and teaching (Secondary) Namibia , Chemistry teachers Attitudes Namibia , Pedagogical content knowledge , Topic-Specific Pedagogical Content Knowledge (TSPCK)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/191986 , vital:45185
- Description: The periodic table of elements is central to the study of chemistry and other disciplines of science, yet Namibian learners do not perform satisfactorily in topics which require its use in answering questions. The purpose of this study, therefore, was to explore how Grade 11 chemistry teachers make use of the periodic table of elements to mediate the learning of writing and balancing chemical equations. The study was carried out with two chemistry teachers in two rural schools in the northern part of Namibia. It was underpinned by an interpretive paradigm, within which a qualitative case study approach was employed. Data were collected through in-depth interviews (semi-structured and stimulated recall interviews), observations, and participants’ group reflections. The latter afforded the participants and myself room to reflect and share ideas at the end of the data gathering process. I used Shulman’s Pedagogical Content Knowledge as my theoretical framework in this study and the data sets were analysed using the five Topic-Specific Pedagogical Content Knowledge (TSPCK) components adapted from Mavhunga and Rollnick. The findings revealed that teachers demonstrated positive attitudes towards the use of the periodic table of elements when teaching the writing and balancing of chemical equations. However, challenges regarding inadequate materials that hindered the teaching and learning process were observed. Another finding of this study was that teachers used a variety of mediation tools such as prior knowledge and appropriate representations to enhance learning. However, during lesson observations, the findings revealed that there was an imbalance in the knowledge of using easily accessible resources as opposed to what teachers had indicated during the semi-structured interviews. Nonetheless, teachers’ group reflections influenced them to analyse and improve their lessons. The study thus recommends that there is a need for continuing professional development for chemistry teachers so that teachers can be afforded opportunities and spaces to share subject matter knowledge, pedagogical content knowledge as well as easily accessible resources that they can use to enhance teaching of chemistry in their classrooms. , Thesis (MEd) -- Faculty of Education, Education, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Kambeyo, Reginald Ndeshipanda
- Date: 2021-10-29
- Subjects: Chemistry Study and teaching (Secondary) Namibia , Periodic table of the elements , Chemical equations Study and teaching (Secondary) Namibia , Chemistry teachers Attitudes Namibia , Pedagogical content knowledge , Topic-Specific Pedagogical Content Knowledge (TSPCK)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/191986 , vital:45185
- Description: The periodic table of elements is central to the study of chemistry and other disciplines of science, yet Namibian learners do not perform satisfactorily in topics which require its use in answering questions. The purpose of this study, therefore, was to explore how Grade 11 chemistry teachers make use of the periodic table of elements to mediate the learning of writing and balancing chemical equations. The study was carried out with two chemistry teachers in two rural schools in the northern part of Namibia. It was underpinned by an interpretive paradigm, within which a qualitative case study approach was employed. Data were collected through in-depth interviews (semi-structured and stimulated recall interviews), observations, and participants’ group reflections. The latter afforded the participants and myself room to reflect and share ideas at the end of the data gathering process. I used Shulman’s Pedagogical Content Knowledge as my theoretical framework in this study and the data sets were analysed using the five Topic-Specific Pedagogical Content Knowledge (TSPCK) components adapted from Mavhunga and Rollnick. The findings revealed that teachers demonstrated positive attitudes towards the use of the periodic table of elements when teaching the writing and balancing of chemical equations. However, challenges regarding inadequate materials that hindered the teaching and learning process were observed. Another finding of this study was that teachers used a variety of mediation tools such as prior knowledge and appropriate representations to enhance learning. However, during lesson observations, the findings revealed that there was an imbalance in the knowledge of using easily accessible resources as opposed to what teachers had indicated during the semi-structured interviews. Nonetheless, teachers’ group reflections influenced them to analyse and improve their lessons. The study thus recommends that there is a need for continuing professional development for chemistry teachers so that teachers can be afforded opportunities and spaces to share subject matter knowledge, pedagogical content knowledge as well as easily accessible resources that they can use to enhance teaching of chemistry in their classrooms. , Thesis (MEd) -- Faculty of Education, Education, 2021
- Full Text:
- Date Issued: 2021-10-29
Exploring ESL teachers’ self-developed pedagogical practices for teaching reading comprehension in Namibian primary schools
- Authors: Alumbungu, Marta Ndakalako
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/419714 , vital:71669
- Description: Embargoed. Possible release date 2026 pending publication. , Thesis (MEd) -- Faculty of Education, Secondary and Post-School Education, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Alumbungu, Marta Ndakalako
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/419714 , vital:71669
- Description: Embargoed. Possible release date 2026 pending publication. , Thesis (MEd) -- Faculty of Education, Secondary and Post-School Education, 2023
- Full Text:
- Date Issued: 2023-10-13
The trade and poverty nexus in South Africa: investigating the transmission mechanism and the associated challenges
- Authors: Bhebhe, Nonceba Fikile
- Date: 2022-10-14
- Subjects: Commerce , Free trade , International trade , Poverty South Africa , Poverty Prevention , South Africa Economic conditions 1991-
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/357515 , vital:64750
- Description: International trade plays an essential role in economic development strategies. In literature, foreign trade is identified as a driver of economic growth. In recent times there has been an expansion in the scope of investigations around the role of international trade to include its links with poverty alleviation. Poverty alleviation is explicitly identified as the first goal on the 2030 agenda for sustainable development under the Sustainable Development Goals and implicitly defined in goal 10. International trade is seen as the engine behind achieving the goal. South Africa records excessive poverty and inequality levels by international standards for a middle-income country. The most recent Poverty Trends Report for 2006 - 2015 reports 55.5% of the population living in poverty. Inequality statistics reported a per capita expenditure Gini coefficient of 0.65 in 2015, evidence that the country has high levels of inequality. The country's severe poverty, unemployment, and inequality prompt policymakers to formulate developmental policies around the underlying structural challenges. Trade openness has increased since the end of the Apartheid era. Despite the increased trade openness, economic growth has been insufficient in reducing the high unemployment and poverty levels, presenting a challenge for economists, who argue that trade openness is pro-growth and pro-poor. In the South African case, the lack of change in the structural challenges of poverty, unemployment and inequality has raised concerns over whether the trade policy reforms made since 1994 interfere with development objectives. This study aims to investigate the impact of trade liberalisation on poverty, using the three channels, namely enterprise, distribution, and government that have been researched within the McCulloch, Winters and Cirera framework. Specifically, it investigates the linkages via the transmission mechanism in which trade affects poverty in South Africa by mapping the transmission mechanisms from trade liberalisation to poverty alleviation, whilst identifying the possible challenges to the transmission mechanisms and lastly, analysing the stylised facts around trade and poverty in South Africa. To answer the question of this study, quantitative data from National Income Dynamic Study (NIDS) was merged longitudinally and aggregated with the industry tariff data sourced from the World Trade Organisation (WTO) and United Nations Conference on Trade and Development (UNCTAD) statistics. A path analysis was undertaken to map the transmission mechanism, whilst descriptive statistics were used to identify the possible associated challenges. The results show that the most significant channel of transmission are the enterprise and distribution channel. However, the effects are of a small margin and a more comprehensive trade policy yield a higher margin of poverty alleviation. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2022
- Full Text:
- Date Issued: 2022-10-14
- Authors: Bhebhe, Nonceba Fikile
- Date: 2022-10-14
- Subjects: Commerce , Free trade , International trade , Poverty South Africa , Poverty Prevention , South Africa Economic conditions 1991-
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/357515 , vital:64750
- Description: International trade plays an essential role in economic development strategies. In literature, foreign trade is identified as a driver of economic growth. In recent times there has been an expansion in the scope of investigations around the role of international trade to include its links with poverty alleviation. Poverty alleviation is explicitly identified as the first goal on the 2030 agenda for sustainable development under the Sustainable Development Goals and implicitly defined in goal 10. International trade is seen as the engine behind achieving the goal. South Africa records excessive poverty and inequality levels by international standards for a middle-income country. The most recent Poverty Trends Report for 2006 - 2015 reports 55.5% of the population living in poverty. Inequality statistics reported a per capita expenditure Gini coefficient of 0.65 in 2015, evidence that the country has high levels of inequality. The country's severe poverty, unemployment, and inequality prompt policymakers to formulate developmental policies around the underlying structural challenges. Trade openness has increased since the end of the Apartheid era. Despite the increased trade openness, economic growth has been insufficient in reducing the high unemployment and poverty levels, presenting a challenge for economists, who argue that trade openness is pro-growth and pro-poor. In the South African case, the lack of change in the structural challenges of poverty, unemployment and inequality has raised concerns over whether the trade policy reforms made since 1994 interfere with development objectives. This study aims to investigate the impact of trade liberalisation on poverty, using the three channels, namely enterprise, distribution, and government that have been researched within the McCulloch, Winters and Cirera framework. Specifically, it investigates the linkages via the transmission mechanism in which trade affects poverty in South Africa by mapping the transmission mechanisms from trade liberalisation to poverty alleviation, whilst identifying the possible challenges to the transmission mechanisms and lastly, analysing the stylised facts around trade and poverty in South Africa. To answer the question of this study, quantitative data from National Income Dynamic Study (NIDS) was merged longitudinally and aggregated with the industry tariff data sourced from the World Trade Organisation (WTO) and United Nations Conference on Trade and Development (UNCTAD) statistics. A path analysis was undertaken to map the transmission mechanism, whilst descriptive statistics were used to identify the possible associated challenges. The results show that the most significant channel of transmission are the enterprise and distribution channel. However, the effects are of a small margin and a more comprehensive trade policy yield a higher margin of poverty alleviation. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2022
- Full Text:
- Date Issued: 2022-10-14
Plant-fungal mutualism as a strategy for the bioremediation of hydrocarbon polluted soils
- Authors: Keshinro, Olajide Muritala
- Date: 2021-10-29
- Subjects: Mutualism (Biology) , Plant-fungus relationships , Bioremediation , Mucilage , Plant exudates , Extracellular polymeric substances , Laccase , Peroxidase , Phytoremediation , Ligninolytic enzymes
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/190918 , vital:45041 , 10.21504/10962/190918
- Description: Inasmuch as coal remains the linchpin for the generation of electricity and liquid petroleum products in South Africa, hydrocarbon waste and coal discard will continue to pose a threat to the environment. Therefore, the onus is on the associated industries to develop and implement efficient and sustainable strategies to mitigate the negative impacts of energy generating activities on the environment. Most conventional efforts in this regard, although successful for soil repair and the initiation of vegetation, have been deemed unsustainable. In an effort to find a sustainable remediation strategy a novel technology termed “FungCoal” was conceptualized and patented as a strategy for the rehabilitation of open cast coal mines, carbonaceous-rich spoils and coal wastes. This biotechnology, which exploits plant-fungal mutualism to achieve effective biodegradation of coal on discard dumps and the breakdown of the carbonaceous component in spoils, promotes revegetation to facilitate rehabilitation of mining-disturbed land. However, one limiting factor of the FungCoal bioprocess is that it requires oxidized weathered coal, a highly complex and variable resource for use as a co-substrate, for growth and proliferation of the coal degrading microorganisms. To fully exploit the potential of plant-fungal mutualism and its interaction for use in the remediation of coal contaminated soils, this study investigated the proposed relationship between plant roots, root exudate and the coal degrading fungus “Aspergillus sp.” (previously Neosartorya fischeri) strain 84 in more detail, in an effort to gain further insight into the mechanisms underpinning plant-fungal mutualism as a strategy for re-vegetation of coal discard dumps and the rehabilitation of hydrocarbon-contaminated soil using the FungCoal approach. A pot-on-beaker (PoB) method was developed for the easy cultivation and collection of extracellular polymeric substance (EPS)-containing exudates from Zea mays L. (maize) and Abelmuschus esculentus (okra). Characterisation of the EPS material from these exudates was carried out using a combination of physicochemical and biochemical methods. The results from analysis of phenolics and indoles showed that exudates contain some form of indoles and phenolic compounds, although in little proportions, which may fulfil a signalling function, responsible for attracting soil microorganisms into the rhizosphere. Spectroscopic analysis of the exudates using FT-IR revealed vibrations corresponding to functional groups of alkanes, alkenes, alkynes, and carboxylic acids. These compounds likely provide an easily accessible source of carbon to soil microorganisms and are also a better alternative to the poly-aromatics which are an inherent component locked-up in the supposed recalcitrant coal material. The results from biochemical analyses also revealed the presence of carbohydrate, proteins, lipids, and low amounts of α-amino-nitrogen in the EPS of maize and okra. These components of EPS are all essential for the stimulation of enzymatic activities in soil microorganisms and, which may in turn aid biodegradation. The action of the root EPS from maize was further tested on three coal-degrading fungal isolates identified as Aspergillus strain ECCN 84, Aspergillus strain ECCN 225 and Penicillium strain ECCN 243 for manganese peroxidase (MnP) and laccase (LAC) activities. The results revealed that the Aspergillus species, strains ECCN 84 and ECCN 225, showed with or without EPS, observable black halos surrounding each of the colonies after 7d incubation indicative of positive MnP activity, while no activity was observed for the Penicillium sp. strain ECCN 243. Analysis for LAC revealed little or no activity in any of the coal degrading fungi following addition of pulverized coal to the growth medium. Interestingly, the addition of EPS-containing exudate to the coal-containing medium resulted in increased LAC activity for all fungal isolates. This finding affirmed the positive contribution of EPS to extracellular LAC activity, purported as an important enzyme in the coal biodegradation process. Finally, the impact of plant-derived exudate on the colonisation and biodegradation of coal was investigated in situ using rhizoboxes, to simulate a coal environment, and was carried out for 16 weeks. Microscopic examination of coal samples after termination of the experiment showed fungal proliferation and attachment to coal particles. All of the rhizoboxes that contained plants had higher medium pH and EC, and the concentration of phenolics, indoles and humic acids was greater than that of control treatments. These observations indicated better rhizosphere colonisation, substrate biodegradation and humification. Therefore, root exudate appears to play a significant role in coordination of soil microorganisms within the rhizosphere and likely serves both as a scaffold for rhizospheric interactions by providing microorganisms with accessible carbon and as a likely ‘trigger’ for induction of coal-degrading enzymes such as fungal LAC for mobilisation of recalcitrant carbon. This study has shown that EPS exuded from roots of Zea mays together with coal degrading fungus Aspergillus strain ECCN 84 can alkalinise the coal substrate and facilitate introduction of oxygen, possibly as a result of increased laccase activity, and increase availability of nutrients (as indicated by higher EC) in a coal-polluted rhizosphere, to provide plants and their associated mycorrhizae and presumably other beneficial microorganisms a more mesic environment for sustained phytoremediation with enhanced rehabilitation potential. In conclusion, this study confirms the positive role of root exudate in mediating a mutualistic rehabilitation strategy involving plants and fungi such as the FungCoal bioprocess. , Thesis (PhD) -- Faculty of Science, Institute for Environmental Biotechnology, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Keshinro, Olajide Muritala
- Date: 2021-10-29
- Subjects: Mutualism (Biology) , Plant-fungus relationships , Bioremediation , Mucilage , Plant exudates , Extracellular polymeric substances , Laccase , Peroxidase , Phytoremediation , Ligninolytic enzymes
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/190918 , vital:45041 , 10.21504/10962/190918
- Description: Inasmuch as coal remains the linchpin for the generation of electricity and liquid petroleum products in South Africa, hydrocarbon waste and coal discard will continue to pose a threat to the environment. Therefore, the onus is on the associated industries to develop and implement efficient and sustainable strategies to mitigate the negative impacts of energy generating activities on the environment. Most conventional efforts in this regard, although successful for soil repair and the initiation of vegetation, have been deemed unsustainable. In an effort to find a sustainable remediation strategy a novel technology termed “FungCoal” was conceptualized and patented as a strategy for the rehabilitation of open cast coal mines, carbonaceous-rich spoils and coal wastes. This biotechnology, which exploits plant-fungal mutualism to achieve effective biodegradation of coal on discard dumps and the breakdown of the carbonaceous component in spoils, promotes revegetation to facilitate rehabilitation of mining-disturbed land. However, one limiting factor of the FungCoal bioprocess is that it requires oxidized weathered coal, a highly complex and variable resource for use as a co-substrate, for growth and proliferation of the coal degrading microorganisms. To fully exploit the potential of plant-fungal mutualism and its interaction for use in the remediation of coal contaminated soils, this study investigated the proposed relationship between plant roots, root exudate and the coal degrading fungus “Aspergillus sp.” (previously Neosartorya fischeri) strain 84 in more detail, in an effort to gain further insight into the mechanisms underpinning plant-fungal mutualism as a strategy for re-vegetation of coal discard dumps and the rehabilitation of hydrocarbon-contaminated soil using the FungCoal approach. A pot-on-beaker (PoB) method was developed for the easy cultivation and collection of extracellular polymeric substance (EPS)-containing exudates from Zea mays L. (maize) and Abelmuschus esculentus (okra). Characterisation of the EPS material from these exudates was carried out using a combination of physicochemical and biochemical methods. The results from analysis of phenolics and indoles showed that exudates contain some form of indoles and phenolic compounds, although in little proportions, which may fulfil a signalling function, responsible for attracting soil microorganisms into the rhizosphere. Spectroscopic analysis of the exudates using FT-IR revealed vibrations corresponding to functional groups of alkanes, alkenes, alkynes, and carboxylic acids. These compounds likely provide an easily accessible source of carbon to soil microorganisms and are also a better alternative to the poly-aromatics which are an inherent component locked-up in the supposed recalcitrant coal material. The results from biochemical analyses also revealed the presence of carbohydrate, proteins, lipids, and low amounts of α-amino-nitrogen in the EPS of maize and okra. These components of EPS are all essential for the stimulation of enzymatic activities in soil microorganisms and, which may in turn aid biodegradation. The action of the root EPS from maize was further tested on three coal-degrading fungal isolates identified as Aspergillus strain ECCN 84, Aspergillus strain ECCN 225 and Penicillium strain ECCN 243 for manganese peroxidase (MnP) and laccase (LAC) activities. The results revealed that the Aspergillus species, strains ECCN 84 and ECCN 225, showed with or without EPS, observable black halos surrounding each of the colonies after 7d incubation indicative of positive MnP activity, while no activity was observed for the Penicillium sp. strain ECCN 243. Analysis for LAC revealed little or no activity in any of the coal degrading fungi following addition of pulverized coal to the growth medium. Interestingly, the addition of EPS-containing exudate to the coal-containing medium resulted in increased LAC activity for all fungal isolates. This finding affirmed the positive contribution of EPS to extracellular LAC activity, purported as an important enzyme in the coal biodegradation process. Finally, the impact of plant-derived exudate on the colonisation and biodegradation of coal was investigated in situ using rhizoboxes, to simulate a coal environment, and was carried out for 16 weeks. Microscopic examination of coal samples after termination of the experiment showed fungal proliferation and attachment to coal particles. All of the rhizoboxes that contained plants had higher medium pH and EC, and the concentration of phenolics, indoles and humic acids was greater than that of control treatments. These observations indicated better rhizosphere colonisation, substrate biodegradation and humification. Therefore, root exudate appears to play a significant role in coordination of soil microorganisms within the rhizosphere and likely serves both as a scaffold for rhizospheric interactions by providing microorganisms with accessible carbon and as a likely ‘trigger’ for induction of coal-degrading enzymes such as fungal LAC for mobilisation of recalcitrant carbon. This study has shown that EPS exuded from roots of Zea mays together with coal degrading fungus Aspergillus strain ECCN 84 can alkalinise the coal substrate and facilitate introduction of oxygen, possibly as a result of increased laccase activity, and increase availability of nutrients (as indicated by higher EC) in a coal-polluted rhizosphere, to provide plants and their associated mycorrhizae and presumably other beneficial microorganisms a more mesic environment for sustained phytoremediation with enhanced rehabilitation potential. In conclusion, this study confirms the positive role of root exudate in mediating a mutualistic rehabilitation strategy involving plants and fungi such as the FungCoal bioprocess. , Thesis (PhD) -- Faculty of Science, Institute for Environmental Biotechnology, 2021
- Full Text:
- Date Issued: 2021-10-29
Perceptions and attitudes towards leadership styles and staff morale in Eastern Cape Provincial Treasury
- Authors: Tsheqane-Sonn, Nandipa
- Date: 2020-12
- Subjects: Leadership --South Africa --Eastern Cape , Employee morale -- South Africa--Eastern Cape
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/50731 , vital:42398
- Description: The Eastern Cape Provincial Government is comprised of 14 departments, including the Provincial Legislature, and ten (10) public entities. The legislative mandate of Eastern Cape Provincial Treasury (ECPT) is delegated by National Treasury to ensure transparency, accountability and sound financial controls in the management of public finances in accordance with the Constitution, PFMA and Treasury Regulations. The focus of the study is to investigate the perceived leadership style that exists at ECPT. Data was collected by means of a survey questionnaire which consisted of closed questions and distributed to a sample of employees at ECPT who hold positions for senior managers, middle managers and other employees outside these categories, such as administrative assistants. The following leadership styles were examined: Autocratic leadership style, Democratic leadership style, Laissez-faire leadership style and Transformational leadership style. The leadership styles were considered as dependent variables, including Intention to resign, while staff motivation was considered to be the dependent variable. Leadership is described as the social process of persuading people to work towards an institutional goal happily, enthusiastically and persistently. The results of the study revealed autocratic leadership was perceived as the most dominant style that exists at ECPT. Recommendations are made to management to pay attention to the autocratic leadership style as this style has been proven by researchers to have a negative effect on employee motivation. Motivation is described as the force within us that stimulates, directs and sustains our behaviour. The research study further explored the perceptions of employees on motivation. Maslow’s hierarchy of needs theory was explored as part of the motivation theories. Results based on this theory revealed that the Physiological needs of staff at ECPT are not met. These needs include biological needs such as water, food and air. Chapter 2 of the Constitution of South Africa states that everyone has the right to have access to sufficient food and water. In light of the constitutional requirements on human rights and legislative environment that ECPT operates in, it is recommended that management ensures employees have access to clean water and basic sanitation and accommodation, particularly in the working environment. McClelland’s needs ix theory revealed that staff at ECPT have a high need for achievement, moderate need for power and a low need for affiliation as respondents remained neutral on whether their needs for affiliation were met. It is recommended that management adopts initiatives such as team building, meeting teams regularly to communicate departmental strategies and to involve staff in decision-making and policy updates. The study confirms that when employees are motivated, they go the extra mile in fulfilling responsibilities and by ensuring that staff morale is considered and boosted, ECPT stands to benefit from a motivated workforce that will lead the department in excelling on its mandate of ensuring that the lives of the people of Eastern Cape are improved. It further adjudicates that the appropriate style of leadership is needed that will augment staff morale. , Thesis (MBA) -- Faculty of Business and Economic Sciences , Business School, 2020
- Full Text:
- Date Issued: 2020-12
- Authors: Tsheqane-Sonn, Nandipa
- Date: 2020-12
- Subjects: Leadership --South Africa --Eastern Cape , Employee morale -- South Africa--Eastern Cape
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/50731 , vital:42398
- Description: The Eastern Cape Provincial Government is comprised of 14 departments, including the Provincial Legislature, and ten (10) public entities. The legislative mandate of Eastern Cape Provincial Treasury (ECPT) is delegated by National Treasury to ensure transparency, accountability and sound financial controls in the management of public finances in accordance with the Constitution, PFMA and Treasury Regulations. The focus of the study is to investigate the perceived leadership style that exists at ECPT. Data was collected by means of a survey questionnaire which consisted of closed questions and distributed to a sample of employees at ECPT who hold positions for senior managers, middle managers and other employees outside these categories, such as administrative assistants. The following leadership styles were examined: Autocratic leadership style, Democratic leadership style, Laissez-faire leadership style and Transformational leadership style. The leadership styles were considered as dependent variables, including Intention to resign, while staff motivation was considered to be the dependent variable. Leadership is described as the social process of persuading people to work towards an institutional goal happily, enthusiastically and persistently. The results of the study revealed autocratic leadership was perceived as the most dominant style that exists at ECPT. Recommendations are made to management to pay attention to the autocratic leadership style as this style has been proven by researchers to have a negative effect on employee motivation. Motivation is described as the force within us that stimulates, directs and sustains our behaviour. The research study further explored the perceptions of employees on motivation. Maslow’s hierarchy of needs theory was explored as part of the motivation theories. Results based on this theory revealed that the Physiological needs of staff at ECPT are not met. These needs include biological needs such as water, food and air. Chapter 2 of the Constitution of South Africa states that everyone has the right to have access to sufficient food and water. In light of the constitutional requirements on human rights and legislative environment that ECPT operates in, it is recommended that management ensures employees have access to clean water and basic sanitation and accommodation, particularly in the working environment. McClelland’s needs ix theory revealed that staff at ECPT have a high need for achievement, moderate need for power and a low need for affiliation as respondents remained neutral on whether their needs for affiliation were met. It is recommended that management adopts initiatives such as team building, meeting teams regularly to communicate departmental strategies and to involve staff in decision-making and policy updates. The study confirms that when employees are motivated, they go the extra mile in fulfilling responsibilities and by ensuring that staff morale is considered and boosted, ECPT stands to benefit from a motivated workforce that will lead the department in excelling on its mandate of ensuring that the lives of the people of Eastern Cape are improved. It further adjudicates that the appropriate style of leadership is needed that will augment staff morale. , Thesis (MBA) -- Faculty of Business and Economic Sciences , Business School, 2020
- Full Text:
- Date Issued: 2020-12
Top-down control by grapsoid crabs in South African estuarine salt marshes
- Authors: Smith, Leigh-Ann
- Date: 2023-04
- Subjects: Salt marsh ecology – South Africa , Crabs --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61223 , vital:69807
- Description: Salt marshes are one of the most productive ecosystems globally. These ‘blue carbon’ habitats are in many respects resilient to climate change effects, able to track sea level rise and act as carbon sinks. Since salt marshes are economically and ecologically essential habitats (for example providing foraging grounds for invertebrates, fish, birds and humans), understanding the processes that control their structure is crucial to best maintain ecosystem services provided by these habitats. For decades the importance of top-down forces, such as grazing, has not been recognised as being important in controlling salt marsh plant productivity. Rather, bottom-up forces, such as the availability of oxygen, was thought to be the main constraint to primary production. Therefore, a better understanding of salt marsh ecosystem dynamics and whether grazer control exists is needed. Although grazer top-down control has been demonstrated in salt marshes in locations such as the United States, this has not been investigated in South Africa. This is a crucial knowledge gap locally considering the importance of salt marsh ecosystems. The aim of this study was therefore to determine what role consumers play in structuring South Africa’s estuarine salt marsh vegetation, thereby also contextualising this process internationally. In order to achieve this, the abundance of grapsoid crabs was estimated and related to key salt marsh features, such as Spartina maritima stem height and stem density, which was quantified from observational surveys. Sampling took place at the beginning and end of the early-spring and late-summer growth period (September 2021 and April 2022) in the Knysna, Kromme and Swartkops estuaries. If a correlation was observed between crab density and salt marsh features, it was important to determine whether they consume the salt marsh vegetation or if the effect was due to their burrowing activities. Hence, the diet of grapsoid crabs was investigated using stable isotope and gut content analysis. To examine the importance of crab grazing in controlling the growth of salt marsh vegetation, crab abundance was manipulated in situ by means of exclusion cages. This experiment ran for five months in the Kromme Estuary, from November 2021 to March 2022 over the salt marsh growing season. An ex situ feeding experiment was also conducted on 30 crab specimens collected from the Kromme Estuary, during May 2022. These crabs were starved for 48 hours and thereafter fed different components of Spartina (growing and dead blades, and roots and rhizomes). The food consumed was quantified as the change in plant length and dry weight after 48 hours, which gave a maximum grazing rate for the different food sources. It was found that crabs are having a minimal impact on the salt marsh vegetation structure. Spartina maritima does form an important component of the diet of grapsoid crabs, however, this is not their only source of food, and possibly not their preferred source of food. They are however contributing to sediment properties through their burrowing activities. The iii ex situ feeding experiment showed that grapsoid crabs can consume all vegetative components of Spartina, with a significantly greater amount of roots and rhizomes consumed. There was no consistent effect in terms of the exclusion of grazers, indicating that other mitigating factors could be reducing the impacts of grapsoid exclusion in situ. Together, these findings contribute knowledge that can be used to inform conservation by quantifying what the salt marsh risks losing in the absence or overabundance of crabs, as has occurred elsewhere globally. These results influence how salt marshes are managed, and highlight how not recognising the importance of consumers, such as crabs, could misalign management objectives. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2023-04
- Authors: Smith, Leigh-Ann
- Date: 2023-04
- Subjects: Salt marsh ecology – South Africa , Crabs --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61223 , vital:69807
- Description: Salt marshes are one of the most productive ecosystems globally. These ‘blue carbon’ habitats are in many respects resilient to climate change effects, able to track sea level rise and act as carbon sinks. Since salt marshes are economically and ecologically essential habitats (for example providing foraging grounds for invertebrates, fish, birds and humans), understanding the processes that control their structure is crucial to best maintain ecosystem services provided by these habitats. For decades the importance of top-down forces, such as grazing, has not been recognised as being important in controlling salt marsh plant productivity. Rather, bottom-up forces, such as the availability of oxygen, was thought to be the main constraint to primary production. Therefore, a better understanding of salt marsh ecosystem dynamics and whether grazer control exists is needed. Although grazer top-down control has been demonstrated in salt marshes in locations such as the United States, this has not been investigated in South Africa. This is a crucial knowledge gap locally considering the importance of salt marsh ecosystems. The aim of this study was therefore to determine what role consumers play in structuring South Africa’s estuarine salt marsh vegetation, thereby also contextualising this process internationally. In order to achieve this, the abundance of grapsoid crabs was estimated and related to key salt marsh features, such as Spartina maritima stem height and stem density, which was quantified from observational surveys. Sampling took place at the beginning and end of the early-spring and late-summer growth period (September 2021 and April 2022) in the Knysna, Kromme and Swartkops estuaries. If a correlation was observed between crab density and salt marsh features, it was important to determine whether they consume the salt marsh vegetation or if the effect was due to their burrowing activities. Hence, the diet of grapsoid crabs was investigated using stable isotope and gut content analysis. To examine the importance of crab grazing in controlling the growth of salt marsh vegetation, crab abundance was manipulated in situ by means of exclusion cages. This experiment ran for five months in the Kromme Estuary, from November 2021 to March 2022 over the salt marsh growing season. An ex situ feeding experiment was also conducted on 30 crab specimens collected from the Kromme Estuary, during May 2022. These crabs were starved for 48 hours and thereafter fed different components of Spartina (growing and dead blades, and roots and rhizomes). The food consumed was quantified as the change in plant length and dry weight after 48 hours, which gave a maximum grazing rate for the different food sources. It was found that crabs are having a minimal impact on the salt marsh vegetation structure. Spartina maritima does form an important component of the diet of grapsoid crabs, however, this is not their only source of food, and possibly not their preferred source of food. They are however contributing to sediment properties through their burrowing activities. The iii ex situ feeding experiment showed that grapsoid crabs can consume all vegetative components of Spartina, with a significantly greater amount of roots and rhizomes consumed. There was no consistent effect in terms of the exclusion of grazers, indicating that other mitigating factors could be reducing the impacts of grapsoid exclusion in situ. Together, these findings contribute knowledge that can be used to inform conservation by quantifying what the salt marsh risks losing in the absence or overabundance of crabs, as has occurred elsewhere globally. These results influence how salt marshes are managed, and highlight how not recognising the importance of consumers, such as crabs, could misalign management objectives. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2023-04
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