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Title: Impact of stress on Saccharomyces cerevisiae during scotch grain whisky fermentation
Author: Cheung, Anne Wai Yin
ISNI:       0000 0004 5349 5465
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2014
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High gravity fermentation has been employed to improve the efficiency and sustainability of the Scotch grain whisky fermentation process. However, the use of high gravity wort creates stressful conditions for the yeast; thus it is important to understand the stress tolerances and responses of distilling yeast. In this thesis, the impact of stress on ethanol tolerance was initially assessed using a number of distilling Saccharomyces cerevisiae strains; one of which, S. cerevisiae D 1 showed the highest ethanol tolerance. Furthermore, variation in ethanol tolerance and genetic integrity was observed between isolates of S. cerevisiae D 1 supplied as creamed and dried yeasts. S. cerevisiae D 1 was then monitored during laboratory and industrial scale grain whisky fermentations, focusing on its stress response under fermentation conditions. There are several interesting findings; first S. cerevisiae D1 utilised proline, which may be a part of the stress response. Second, the results also showed the general stress response was activated in the early stages of fermentation and was being taken over by individual stress responses as fermentation proceeded. The results suggest the yeast may also have been stressed as a consequence of the propagation process. Furthermore, expression of ethanol stress response genes were responded to changes in intracellular ethanol concentration. These results provide insight into the stress response of yeast under fermentation conditions and will provide valuable information for developing future yeast strains suitable for high gravity fermentation. Finally, the identification of presumptive lactic acid bacteria isolated from the fermentation was also studied. The result highlighted the diversity of the microflora presented and, as lactic acid bacteria is desirable for their contribution to flavour, better understanding of the microflora could lead to an improved flavour profile.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available