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 are suitable 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 also demonstrated 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 wall stresses were examined. The growth of the mut1 strain in the presence of ethyl n-caproate and 3-methyl butyl acetate, which were metabolic derivatives of ethanol, was found to be less than the wild type. On the other hand, the growth of the mut1 strain in the presence of 50% (w/v) sucrose and 1M NaCl was similar to that of the wild type. The sensitivity to cell wall digestiveenzyme, zymolyase, was also similar in both wild and mut1 strains. Finally, the mut1 strain showed resistance to homocysteine and serine but was sensitive to methionine. These results suggest that the ethanol resistance of the mut1 strain may be more related to the ethanol metabolic and signalling pathways rather than the enhanced stress resistances relating to the membrane or cell wall compositions.