Influence of sodium chloride on wine yeast physiology and fermentation performance

This thesis concerns research into the influence of salt on physiology of the yeast, <i>Saccharomyces cerevisiae</i>. Specifically, the work focused on how sodium chloride affected the growth, viability and fermentation performance in industrial (winemaking) strains of this yeast in both laboratory-scale and industrial-scale experiments. Comparative fermentations were also conducted with selected non-<i>Saccharomyces</i> yeasts that are of relevance in enology. One of the main findings of the research presented involved the influence of salt "preconditioning” of yeasts which represents a method of pre-culturing cells in the presence of salt in an attempt to improve subsequent fermentation performance. Such an approach resulted in preconditioned yeasts having an improved capability to ferment high-sugar containing media with increased cell viability and with elevated levels of produced ethanol. Salt-preconditioning was most likely influencing the stress-tolerance of yeasts by inducing the synthesis of key metabolites such as trehalose and glycerol which act to improve cells’ ability to withstand osmostress and ethanol toxicity. The industrial-scale trials using salt-preconditioned yeasts verified the benefit of the physiological engineering approach to practical winemaking fermentations. Benefits were also observed in a specialized fermentation system (WITY produced by the first letters of the words Wine, Immobilization, Tower, and Yeast) that utilized immobilized yeast. Overall, this research has demonstrated that a relatively simple method designed to physiologically adapt yeast cells - by salt-preconditioning - can have distinct advantages for alcohol fermentation processes.

Name dc:type.qualificationname

PhD

Level dc:type.qualificationlevel

Doctoral Thesis

Grantor dc:publisher.institution

University of Abertay Dundee

Year dc:date.issued

2009

Author dc:creator

• Logothetis, Stelios

Advisor dc:contributor.advisor

• Walker, Graeme

Language dc:language

eng

Identifier

oai:rke.abertay.ac.uk:studenttheses/a0f2a914-5c98-4dad-bf79-69abbb360595

OAI identifier oai:identifier

oai:rke.abertay.ac.uk:studenttheses/a0f2a914-5c98-4dad-bf79-69abbb360595