THE INVOLVEMENT OF TREHALOSE IN YEAST STRESS TOLERANCE

A total of 12 yeast strains from various genera were examined for their ability to produce ethanol in the presence of high concentrations of glucose. From these studies, the yeasts Torulaspora delbrueckii and Zygosaccharomyces rouxii were observed to be the most osmotolerant. These osmotolerant yeast strains were also observed to possess high concentrations of intracellular trehalose. Furthermore, these strains were found to be tolerant to long-term storage at -20-degrees-C and to storage at 4-degrees-C in beer containing 5% (v/v) ethanol. Cells containing high trehalose levels at the time of freezing or cold storage exhibited the highest cell viabilities. Trehalose concentration was observed to increase during growth on glucose, reaching a maximum after 24-48 h. Increasing the incubation temperature from 21 to 40-degrees-C also resulted in an increase in intracellular trehalose content. These results suggest that trehalose plays a role in enhancing yeast survival under environmentally stressful conditions.