ANALYSIS OF SENSITIVITY TO HIGH-TEMPERATURE OF TORULASPORA-DELBRUECKII NO-110

The alcohol-fermenting yeast Torulaspora delbrueckii No, 3110 was less tolerant to high temperature than Saccharomyces cerevisiae IFO 0224 as measured by alcohol fermentation during mild agitation: at 40 degrees C, ethanol production of the two yeasts was 0.8 and 5.2 wt% respectively. The No. 3110 cells had much unsaturated fatty acid (C18:2) and little ergosterol, which suggests that the low tolerance might be caused by high membrane fluidity, Two types of miconazole-resistant mutants were isolated and characterized, Strain M47 had less unsaturated fatty acid and was found to be more temperature tolerant than No, 3110, Strain M59 was defective in ergosterol synthesis and was less temperature tolerant than No, 3110, These results indicate the importance of membrane rigidity in temperature tolerance. M59 accumulated much less trehalose than No, 3110 did, Addition of trehalose to the permeabilized cell system of M59 restored the temperature sensitivity, but not when the trehalase inhibitor deoxynojirimycin was also added, which suggests that the accumulation and metabolism of trehalose is important for the expression of temperature tolerance.