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Now showing 1 - 6 of 6
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    Genomic and transcriptomic analyses of epsilon-poly-L-lysine producing Streptomyces albulus
    (2018) Crosse, Amanda Jane
    Biodiesel production has increased significantly in the past 15 years since it offers a renewable solution to fossil fuels. This production increased the availability of the process’s by-product, crude glycerol. Crude glycerol contains harmful contaminants and with expensive disposal options, often ends in landfill sites where it causes environmental problems. Crude glycerol conversion to valuable products enhances value and aides with disposal problems. Streptomyces albulus was shown to utilize biodiesel-derived crude glycerol as a sole carbon source. Commercially the bacterium is used to synthesize useful secondary metabolites from glucose, e.g. ε-poly-L-lysine (ε-PL). This work aimed to provide a genomic platform for genetic engineering to optimize the production of key secondary metabolites. The first draft genome of S. albulus was sequenced and annotated, together with several relevant transcriptomes. Bio-informatic assessment identified potential genes and pathways involved in glycerol, glucose and ε-PL metabolism. Additionally, 56 silent secondary metabolite gene clusters not previously known, were also identified. Transcriptionally active gene candidates were confirmed by sequencing transcriptomes for different carbon sources (glucose and pure glycerol) over the course of exponential to stationary growth phases – phases linked to ε-PL metabolism. Analyses revealed that the glucose transporter and glycerol uptake facilitator proteins’ differential expressions halved with a pH drop. Glycerol kinase’s and glycerol-3-phosphate dehydrogenase’s (aerobic isoenzyme) relative expression levels decreased with a similar factor, though glycerol-3-phosphate dehydrogenase (anaerobic isoenzyme) showed an increase. Aspartokinase relative expression levels during ε-PL synthesis remained high for both carbon sources, thereby providing S. albulus with sufficient L-lysine monomers during production. Interestingly, ε-PL synthase and both ε-PL degrading enzymes were expressed throughout the growth cycle of S. albulus with both carbon sources, but with ε-PL synthase levels higher at pH 3 than pH 5. This infers that the activity of these enzymes may be more reliant on pH, or substrate availability, than gene expression levels. Genomics, transcriptomics and culturing analyses revealed S. albulus as a halotolerant microorganism. Indeed, three of the four genes of the ectoine pathway, a hydroprotectant, were upregulated with increased salt concentrations. Interestingly the glycerol operon is also upregulated under the high salt concentrations.
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    Biodiesel production with waste product cycling
    (2018) Makhale, Itumeleng
    Bio-derived fuels such as biodiesel and bioethanol have gained considerable attention as liquid transport fuels. Economic viability for large-scale bio-based fuel production in South Africa remains a contentious issue. This study aims to describe an enzymatic biodiesel production process, with a greater goal to stimulate small-scale biodiesel production in and around the country. The possibility of using an E. coli host strain to develop a bacterial-biodiesel generating system was considered utilising a synthetic lipase for the trans-esterification of sunflower oil. The conditions for expression were evaluated with induction trials at 30 and 37 °C respectively; the concentration of IPTG was adjusted in 0.25 mM increments from 0 to 1 mM. The ideal concentration of IPTG was 0.75 mM, and the ideal temperature was 37 °C. The lipase's hydrolytic capacity was further evaluated on para-Nitrophenol palmitate, and the catalytic amount necessary was determined to be below 0.00729 µg for the substrate concentrations employed.
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    Catalytic production of biodiesel from waste cooking oil using calcium silicate
    (2018) Ntinugwa, Ndubuisi Ebenezer
    The production of biofuels has witnessed a renewed interest in light of finding alternatives to fossil fuels. One such important biofuel is biodiesel. Biodiesel made from waste vegetable oil (WVO) is particularly favorable due to the availability of waste as fuel source as opposed to oil derived from food plants. Biodiesel production can therefore loom as a large economic opportunity for South Africa, whose fuel is largely imported from crude-oil rich regions in the world. Despite the environmental benefit compared to the fossil fuel, bio-fuels production at industrial level is not currently financially attractive in comparison to the conventional diesel fuel prices. The market price of the produced biofuel depends on its feedstocks, which fluctuate significantly and affect the production cost. The purpose and aim of this research project is to combine and investigate the optimum conditions and the elementary reaction kinetics for the production of biodiesel from waste vegetable oil using a calcium silicate catalyst. The optimum conditions of interest are the methanol to oil ratio and the catalyst concentration. There are various methods available for the production of biodiesel. For this project, transesterification was discovered to be the most suitable, and was then used throughout during the experiment. Prior to the production of biodiesel the catalyst was prepared from a reaction containing calcium hydroxide and silica gel as the reactants. The catalyst was characterized using FTIR, BET, XRD and SEM determinations. The waste vegetable oil was also characterized in order to determine its free fatty acid (FFA) content, its density and its moisture content; which are all essential to the quality of biodiesel that could be produced. The biodiesel produced was confirmed using GCMS and its quality in terms of concentration was derived from its absorbance using an absorbance vs. concentration calibration curve. The results show that the optimum methanol to oil ratio at a constant temperature of 60 ℃, with a reaction time of 180 minutes is 3:1. The optimum catalyst concentration at the same reaction temperature and time was found to be 5%. The transesterification reaction in this project correlated to an irreversible first order kinetic model. The reaction kinetics depicted this catalyst as ineffective for transesterification since low reaction rates were observed
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    Modelling the production of biodiesel from non-edible oils (Jatropha curcas oil and Tobacco seed oil (TSO): a kinetic study
    (2017) Mthembu, Feziwe Celile
    The significant increase in the primary energy demand and the effort to reduce harmful emissions related to the greenhouse gases enhanced the search for alternative energy. Production and modelling processes of biofuel from non-edible oil sources assist in the process development of an environmentally friendly fuel such as biodiesel. This work focused on the kinetic modelling of biodiesel synthesised from non-edible oils. Two types of non-edible oils (Jatropha curcas seed oil and Tobacco seed oil) were used in this study including the development of the kinetic behaviour of the transesterification reaction. A linear polynomial model was generated from experimental data found in literature in order to study the influence of operating parameters during biodiesel production. It was found that the temperature improves the yield of biodiesel; this is attributed to the fact that temperature affects the reaction rate constants; and the higher the reaction rate, the lower the activation energy required for a reaction to occur. The optimum conditions for the transesterification of Jatropha curcas seed oil are a temperature of 55 0C, methanol to oil ratio of 6:1, catalyst concentration of 1.2% KOH (by volume of oil), and agitation speed range of 0-250 rpm. Results from both the homogeneous and heterogeneous reactions of Jatropha curcas oil and tobacco seed oil were used to verify the theoretical kinetic and empirical models. It was found that both models describe the kinetic behaviour of transesterification with minor deviations in the estimated parameters. However, the use of empirical model in determining the reaction order, as opposed to the theoretical assumption, gave a second order with respect to oil triglycerides at a temperature of 60 0C. The theoretical kinetic model gave a first order with respect to oil triglycerides. In this case, the activation energy was found to be 71.83 kJ/mol and pre-exponential factor was found to be 2.48 x1010. More investigation should be done to describe the kinetic behaviour of biodiesel production from non-edible oil in order to confirm the correct reaction order and why there is change in reaction order when the temperature increases above 60°C.
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    Transesterification of animal fat to biodiesel over solid hydroxy sodalite catalyst in a batch reactor
    (2017) Makgaba, Chabisha Precious
    Owing to the ongoing advancement in technology, escalating population sizes and urbanization rate, fossil fuels (coal, petroleum oil and natural gas) remain attractive as an energy source to run most of the daily operations. Consequent to heavy consumption of fossil fuels, the world faces detrimental challenges such as future energy security and environmental concerns. Combustion of fossil fuels results in emission of greenhouse gases such as CO2 and SO2 thereby contributing to global warming and acid rain problems. These alarming challenges drive the need for exploration of alternative energy sources to reduce dependence on fossil fuels. Presented in this dissertation is a study of biodiesel, a biodegradable, non-toxic and environmentally benign energy source as an alternative to petroleum-based fuels. Chemically known as fatty acid alkyl ester (FAAE), biodiesel is commonly produced from vegetable oils or animal fats in addition to methanol by a catalysed transesterification reaction. Currently, biodiesel is more expensive than petroleum diesel due to high operation costs incurred during the production process. Despite the high prices, biodiesel production continues to grow on an industrial scale across the world as supported by policy measures and biofuel targets. Researchers have identified two main factors that contribute to high costs of biodiesel production; 1) type of feedstock and 2) type of catalyst used in the production process. Conventional methods of production use edible oils as feedstock. This becomes unjustified due to the potential price hikes in the food market owing to the prospective competition between fuel and food industries. As a result, numerous researchers reported on the use of cheap and non- edible feedstock oils such as waste cooking oil and animal fat. However, the challenge with the use of non-edible oils is their high content of free fatty acids (FFA) which is unattractive for a smooth transesterification process, more especially when homogeneous base catalysts are used. Homogeneous base catalysts are widely used in current industrial biodiesel production methods because they yield faster transesterification processes due to increased reaction rates. However, these types of catalysts are much sensitive to FFA, so when high FFA content feedstock is used, a saponification reaction occurs which consequently reduces the yield of biodiesel. An additional process unit is required to reduce the FFA content via esterification process prior to the main transesterification reaction. Furthermore, since the reaction mixture is homogeneously combined with the product, an additional process unit for product separation is required to recover the resulting biodiesel from the mixture, translating into additional production costs. Researchers are currently exploring the use of heterogeneous catalysts, which tend to avoid the saponification reaction and reduce the need for an esterification reaction used as oil pre-treatment step to reduce FFA content. This dissertation is therefore dedicated to attaining a economic and environmentally attractive process for biodiesel production using cheap non-edible beef tallow oil (BTO) and a heterogeneous hydroxy sodalite (H-SOD) catalyst. Some industrial operations such as zeolite manufacturing processes produce a low grade H-SOD as by products, which is in turn disposed as chemical waste and therefore induces ground water contamination concerns. Exploration on the use of H-SOD as catalyst can largely contribute to the environmental protective measures as a waste management process among other benefits. The use of H-SOD is extensively reported in current research development on membrane separation; limited research reports on the use of H-SOD material to catalyse chemical processes are present in literature. For the first time in open literature, H-SOD is reported as the solid catalyst for biodiesel production in this dissertation. The investigative study commenced with a preliminary study to gauge the feasibility of using H-SOD as a catalyst where a batch transesterification of waste cooking oil (WCO) was studied. The reaction was conducted at 60 ᵒC for 12 h at a methanol-to-WCO ratio of 7.5:1 using 3 wt. % H-SOD catalyst with a particle size of just below 300 Å, the stirring intensity was kept at 1000 rpm to ensure uniform mixing throughout the reaction. The product obtained after the reaction was analysed using a pre-calibrated Chromatography-Mass Spectrometer (GC-MS) described in Chapter 5, and the results demonstrated the possibility of catalysing a transesterification reaction using solid H-SOD. Under the same reaction conditions, the study was then extended to an investigation on the use of H-SOD to catalyze transesterification of BTO (4.53 % FFA) to FAME. The results showed that FAME was produced, at a yield of 39.6% and a conversion of 68.4%. Seeing that the yield and conversion obtained is relatively small compared to literature findings, the effect of some process conditions on the conversion and biodiesel yield were studied. The transesterification reaction was conducted with variations in the mixing intensity (700 – 1250 rpm), catalyst particle size (200 – 300 Å), reaction time (6 – 24 h) and reaction temperature (40-60 °C). The maximum performance of H-SOD catalyst for a transesterification of BTO was achieved with a conversion of 78.3% and biodiesel yield of 62.9% obtained at optimum conditions: a stirrer speed of 1000 rpm, with the smallest catalyst particle size of 200 Å at maximum temperature of 60 °C and 24 h reaction time. The values of activation energy, reaction constants and frequency factor obtained from the kinetic study were 0.0011 min-1, 5.52 x108 min-1 and 79.20 kJ/mol, respectively, and are within the range of the results reported in literature. As a result, solid H-SOD is recommended as a catalyst for the batch transesterification of BTO in a biodiesel production process.
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    Challenges in recycling used cooking oil to produce biodiesel in Polokwane
    (2016) Ramuedzisi, Humbelani Elson
    In response to the ever increasing problems associated with climate change, and greenhouse gas emissions, many countries in the world are developing and adopting climate change resilient policies that support green economy. Green economy sector in South Africa has not as yet received much expected attention as a key sector to address economic and environmental problems. The use and the production of renewable fuels, such as biodiesel are known to have significant economic and environmental benefits. However, progress in the production of biodiesel is hampered by limits imposed by government on the use of fresh vegetable extracted oils for production of biodiesel, mainly due to challenges on food security; and the impact this will have on food prices. In recent years recycling has become an important tool to address waste problems; pollution control; and socio-economic problems such as joblessness, poverty and social inequity. Used cooking oil has always been considered waste and an environmental burden. Therefore through technology advancement of recycling, wastes such as used cooking oil have become useful resources for biodiesel production. This research is about the challenges in recycling used cooking oil to produce biodiesel. The study recommended that in order to address challenges facing sustainability of our environment, and high unemployment rate; small recycling industries such as those operating in Polokwane will need government support such as biodiesel sector policies and regulations, to encourage investment in the biodiesel value chains in a way that will lead to the achievement of green economy goals.