Characterization of an Interesting Novel Mutant Strain of Commercial Saccharomyces cerevisiae

The yeast strains that are resistant to high concentration of ethanol have biotechnological benefits and aresuitable models for physiology and molecular genetics research fields. A novel ethanol-tolerant mutant strain,mut1, derived from the commercial Saccharomyces cerevisiae showed higher ethanol production, and alsodemonstrated resistance to ethanol but not to other alcohols, such as methanol, 2-propanol, and 1-butanol. To characterize mut1, the strain’s resistance to other organic compounds and osmotic and cell wallstresses were examined. The growth of the mut1 strain in the presence of ethyl n-caproate and 3-methyl butylacetate, which were metabolic derivatives of ethanol, was found to be less than the wild type. On the otherhand, the growth of the mut1 strain in the presence of 50% (w/v) sucrose and 1M NaCl was similar to that ofthe wild type. The sensitivity to cell wall digestive enzyme, zymolyase, was also similar in both wild andmut1 strains. Finally, the mut1 strain showed resistance to homocysteine and serine but was sensitive tomethionine. These results suggest that the ethanol resistance of the mut1 strain may be more related tothe ethanol metabolic and signalling pathways rather than the enhanced stress resistances relating to themembrane or cell wall compositions.