3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Characterisation of South African indigenous microalgae for biofuel production potential(2019) Grobler, JasperBio-energy has been widely studied as a renewable energy source. One of the main challenges of traditional bio-energy is that it competes with local food and agriculture industries for feedstock and arable land. Bio-energy derived from a microalgal biomass feedstock has the potential to be used without competing with agriculture and food industries. Bio-diesel and bio-ethanol can be generated from cellular lipids and carbohydrates, respectively, isolated from microalgal biomass. In this study we evaluated the potential of South African indigenous microalgae for use in bio-diesel and bio-ethanol production by firstly identifying an isolate suitable for biofuel production, suitable cultivation medium and analysing bio-fuel properties. Fifteen South African indigenous microalgal isolates from the Microalgal Culture Collection of South Africa (MiCCSA) were cultivated at 2 L scale and characterised to derive their bio-fuel production potential. The isolate referred to as WCB 4.1, identified as Acutodesmus bajacalifornicus, showed good potential for use in bio-energy production, and was used in subsequent studies throughout the work. To explore the potential of increasing lipid, carbohydrate and yield rates of WCB 4.1, eleven potential microalgal cultivation mediums were identified. WCB 4.1 showed the highest growth rate in the JG medium (in-house formulation), with a competitive growth rate of 0.47 d-1. WCB 4.1 showed the highest biomass productivity in the Hase medium, with a relatively low productivity of 53.1 mg/L/d. To be able to fully understand the effect different cultivation mediums have on the cultivation of WCB 4.1, the effect of medium variation on biomass biochemical composition was considered. The bio-diesel yield rate of WCB 4.1 grown in four of the cultivation mediums was superior to that of first-generation bio-energy crops. However, the bio-ethanol yield rate from WCB 4.1 was inferior to first generation bio-energy crops. Utilising bio-diesel property predictive formulas it was possible to predict the properties of bio-diesel generated from WCB 4.1 biomass cultivated in eleven different mediums. It was found that WCB 4.1 biomass from eight of the mediums adhered to South African summer grade bio-diesel standards. WCB 4.1 shows potential to become a commercially competitive strain for bio-energy production, which can produce more bio-diesel per hectare annually than traditional food crops. The bio-energy yield rates of WCB 4.1 do however need some improvement to be able to have bio-energy productivities similar or higher than microalgal bio-energy productivities described by other sources. The key to unlock the potential of WCB 4.1 would be in further process development and improvement.Item Investigating the genes for bile acid metabolism in nocardioform bacteria(1991) Brown, Sharon TeresaNocardioform bacteria were studied for their ability to interconvert bile acids. From the studies of utilisation and resistance curves, the most suitable donor and recipient strains for complementary gene cloning, were Arthrobacter oxydans strain C1 and Rhodococcus erythropolis strain ATCC 4217-1 respectively. [Abbreviated Abstract. Open document to view full version]Item Dynamics of biotechnology entrepreneurship in South Africa and Brazil(2014-08-04) Alagbaoso, Manessah ObinaliBiotechnology entrepreneurship is a relatively new and distinct field of entrepreneurship. Most current empirical research is conducted in the developed economies and cannot be directly extrapolated to the developing economies. The paucity of empirical research and the lack of a conceptual framework for biotechnology entrepreneurship constitute gaps that this research addressed through the development of a proposed theoretical framework of biotechnology entrepreneurship based on empirical research conducted within the context of the developing economies of South Africa and Brazil. The current methodological approaches to research in biotechnology entrepreneurship predominantly make use of a nomothetic philosophical approach and employs quantitative methods. Current research is also often based on surveys conducted within one developing economy context. Consequently, few studies in biotechnology entrepreneurship use the qualitative multiple case study approach. This methodological gap is addressed in this research through the use of qualitative multiple case studies, in the idiographic philosophical tradition, in two developing economies; South Africa and Brazil. The data collection process included in-depth interviews, documents review and observations, which improved the quality of the research through data triangulation. Ten themes were identified, which formed the basis for developing the proposed theoretical framework. In addition, seven factors that influence the process of biotechnology entrepreneurship in South Africa and Brazil were identified as regulation; funding; infrastructure; skills; entrepreneurial and commercialisation capabilities; market for biotechnology products; and social development. This research shows that the individual-opportunity nexus of entrepreneurship does not entirely hold for biotechnology entrepreneurship in South Africa and Brazil. Instead, there is a nexus of research and development; and a governmentincentivised environment that is conducive for biotechnology entrepreneurship. The policy implications of these dynamics in South Africa and Brazil; as well as implications for the other stakeholders in the biotechnology industry are articulated as being linked to the control of the factors that influence biotechnology entrepreneurship by the various stakeholders. Hence, the implications for government are predominantly linked to regulation and infrastructure; and the implications for the other stakeholders are predominantly linked to funding and skills.Item Effect of gold nanoparticles on the activity of perovskites for CO oxidation(2011-11-18) Mokoena, Lebohang VivaciousGold has for many years been regarded as being inert and catalytically inactive compared to the PGMs (platinum group metals). However, in the past decade it has attracted a lot of interest as both a heterogeneous and a homogenous catalyst and has been shown to catalyse a wide range of reactions e.g. oxidation, hydrogenation and reduction among others. Highly dispersed gold nanoparticles on metal oxides, like titanium oxide (Degussa, P25) have predominantly been studied because they yield some of the most active and stable catalysts. Modification of the catalysts and/or supports has been shown to affect their catalytic properties. Likewise, perovskites, which can be manipulated by partial substitution, are reported to be active supports for CO oxidation, but only at high temperatures with no activity shown for temperatures below 200°C. In this study, these perovskites were investigated at low temperatures (below 100°C) with improved activity found upon gold deposition. The presence of gold nanoparticles therefore significantly enhanced the catalytic activity, while the support itself was suspected to be involved in the reaction mechanism. A series of perovskites of the type ABO3 (LaMnO3, LaFeO3, LaCoO3 and LaCuO3) were prepared using the citrate method, while the gold was deposited on them using the deposition-precipitation method. The supports were calcined at different temperatures for optimisation. The catalysts were tested for carbon monoxide oxidation and the active catalysts characterised by XRF, XPS, XRD, Raman spectroscopy and BET surface area measurements. With the support calcined at 800ºC, the best catalyst was then modified and compared with the unmodified catalyst. The 1-wt%Au supported on LaFeO3 was found to give the best catalytic performance. This support was then modified with various weight loadings of calcium to determine the effect of calcium on the catalytic activity. Calcium-doped materials showed decreased surface area, poorer crystallinity and a drop in catalytic activity relative to the Au-LaFeO3 which indicated the best results for CO oxidation. In addition, Au-LaFeO3 showed online stability over 21 hours. Calcining the support improved the incorporation of gold nanoparticles into the perovskite lattice, resulting in superior catalytic activity. Nevertheless, at higher calcination temperatures, the catalytic activity of Au-CaTiO3 was depressed while that of Au-LaFeO3 was enhanced. The activity of perovskites increased upon gold deposition. XPS, revealed that in the active catalysts, both cationic and metallic gold co-existed, whilst in the inactive catalysts the gold existed predominantly either as cationic or metallic gold.