Thermotolerant Yeast Kluyveromyces marxianus Reveals More Tolerance to Heat Shock than the Brewery Yeast Saccharomyces cerevisiae

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The thermotolerant yeast Kluyveromyces marxianus, growing at high temperature (45℃) , showed stronger survival under heat shock at 50℃ than the brewing yeast Saccharomyces cerevisiae, which was unable to grow at 45℃. The survival rate of K. marxianus decreased to 10% during heat shock at 50℃ for 20 min, and to less than 0.01% at 60℃ for 20 min. Cells with damaged cellular membranes were infrequently observed at 50℃ and had decreased significantly from heat shock at 60℃. The metabolic activity of K. marxianus was retained at 50℃, whereas that of S. cerevisiae was not. The trehalose content of K. marxianus was approximately two times that of S. cerevisiae. These results suggest that K. marxianus protects itself from heat shock-induced damage through the use of trehalose (a protective molecule in S. cerevisiae) as well as other different factors.