Masters Degrees (Viticulture and Oenology)

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Browsing Masters Degrees (Viticulture and Oenology) by browse.metadata.advisor "Bester, Michael C."

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    Chitin synthesis in response to environmental stress
    (Stellenbosch : Stellenbosch University, 2014-04) Pauw, Marina; Bauer, Florian; Ndlovu, Thulile; Bester, Michael C.; Stellenbosch University. Faculty of AgriSciences. Dept. of Institute for Wine Biotechnology.
    ENGLISH ABSTRACT: Previous studies have indicated that fermentation with yeast strains whose cell walls contain higher chitin levels may lead to reduced wine haze formation. In order to adjust cell wall chitin levels, more information on the regulation of chitin synthesis in wine-relevant yeast is required. Yeast cells are known to increase chitin levels when subjected to certain environmental changes such as an increase in temperature. The main aim of this project was to investigate chitin accumulation and synthesis in wine yeast strains when exposed to environmental change. This was achieved by subjecting the strains to various environmental conditions and comparing chitin levels. The information gained may aid future selection and/or manipulation of yeast strains for the production of higher chitin levels. Three Saccharomyces cerevisiae strains and two Saccharomyces paradoxus strains were subjected to conditions that had been linked to a change in chitin synthesis in past studies in laboratory yeast strains. Of the conditions used in this study, the addition of calcium to a rich media led to the highest cell wall chitin levels. The data also show that chitin synthesis is largely strain dependant. Two conditions which resulted in increased chitin deposition were chosen for gene expression analyses, using strains with strongly diverging average chitin levels. Results showed that an increase in chitin levels correlates with an increase in expression of GFA1, the gene encoding for the first enzyme of the chitin synthesis pathway. Overall, this study provides novel insights into chitin synthesis in Saccharomyces cerevisiae wine yeast strains as well as Saccharomyces paradoxus strains, with possible future implications on haze prevention studies.