Browsing Masters Degrees (Institute for Wine Biotechnology) by Subject "Bioremediation potential of yeast"
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- ItemEngineered yeast and microalgae mutualisms: Synthetic ecology applied to species isolated from winery wastewater(Stellenbosch : Stellenbosch University, 2018-03) Simpson, Zoe Faith; Bauer, Florian; Naidoo, Rene K.; Stellenbosch University. Faculty of AgriSciences. Dept. of Viticulture and Oenology. Institute for Wine Biotechnology.ENGLISH ABSTRACT: Large volumes of winery wastewater, classified as biodegradable industrial effluent, are generated annually. The development of a cost-effective treatment system is difficult due to the variable and batch nature of winery wastewater. Research has focused on the development of dynamic biological treatment systems using microorganisms including yeast and microalgae, as it has become apparent that these microbes have bioremediation capabilities in various wastewaters. However, no biological winery wastewater treatment system, employing multi-species ecosystems with known species of yeast and microalgae, currently exists. In this study, yeast and microalgae were previously isolated from natural winery wastewater. The first aim of this study was to characterise the bioremediation potential of the yeast, Saccharomyces cerevisiae, and microalga, Parachlorella beijerinckii, in synthetic and raw winery wastewater. P. beijerinckii was physiologically characterised and was able to tolerate salinity and ethanol levels commonly associated with winery wastewater, making it a suitable candidate for further bioremediation studies. Both S. cerevisiae and P. beijerinckii were able to decrease the chemical oxygen demand of winery wastewater and P. beijerinckii monoculture was able to increase the pH of the acidic wastewater. S. cerevisiae out-competed P. beijerinckii in co-culture growth experiments. Interestingly, yeast growth was improved in the presence of the microalgae in this system, suggesting a potential for symbiotic association. The increased yeast growth however had no impact on the bioremediation potential of the co-culture system. To overcome this drawback, a synthetic ecology approach was used to engineer stable symbiotic associations between these evolutionarily unrelated strains of yeast and microalgae. Engineered mutualisms between S. cerevisiae and P. beijerinckii were established under strongly selective conditions based on the nutrient exchange of carbon and nitrogen. These mutualistic associations were relatively easy to establish as the complementary metabolic abilities of each organism were key elements in the mutualism design. The impact of temperature and pH were assessed in these obligatory mutualistic conditions to determine whether the co-culture functions optimally in specific environmental conditions and whether such conditions are similar or different from the optimal conditions required for single species growth. Experiments were first conducted in small scale and continued in larger scale bioreactor studies. The bioreactor conditions were evaluated to generate a more constant continuous culture system. Such continuous culture system would provide an ideal tool to conduct studies on the evolutionary development of mutualistic associations, and may be the first step in developing a multi-species approach to winery wastewater treatment with enhanced bioremediation capabilities. We propose that in the long run such co-culture systems might serve to overcome the limitations associated with single culture system and might improve biotechnological processes.