Effect of Trehalose Accumulation on the Intrinsic and Acquired Thermotolerance in a Natural Isolate, Saccharomyces cerevisiae KNU5377

The difference in the thermotolerance between Saccharomyces cerevisiae KNU5377 and ATCC24858 was compared by assaying the amounts of trehalose accumulated under growth and heat shock conditions. Both strains exhibited similar trehalose accumulation during the growth period, but an intrinsic thermotolerance was much higher in KNU5377 than in the control strain. This result implied that some strain-specific characteristics of KNU5377, other than trehalose accumulation, primarily were responsible fur its higher intrinsic thermotolerance. Heat shock at $43^{\circ}C$ for 90 min to the exponentially growing cells resulted in the maximum level of trehalose In both strains. Trehalose accumulated at least twice more in KNU5377 by the heat shock than in the control, due to the maintenance of its neutral trehalase activity even after the heat shock. Consequently, the Increase of acquired thermotolerance in both strains correlated with an increase in the trehalose content in each strain. In conclusion, KNU5377 exhibited a well-modulated trehalose-related mechanism to accumulate more trehalose by means of maintaining neutral trehalase activity after heat shock than the control strain, thereby contributing to its acquired thermotolerance.