Characterization of an interesting novel mutant strain of commercial Saccharomyces cerevisiae

Document Type: Research Paper

Authors

1 Department of Genetics, Faculty of Sciences, University of Shahrekord, P.O. Box 115, Shahrekord, I.R. Iran.

2 Departmemt of Microbial Biotechnology, Faculty of Sciences and New Technologies, University of Isfahan, P.O. Box 81745-331, Isfahan, I.R. Iran.

3 Department of Biology, Faculty of Sceinces, University of Isfahan, P.O. Box 81745-141, Isfahan, I.R. Iran.

4 Department of Applied Molecular Bioscience, Graduate School of Medicine, Yamaguchi University, Tokiwadai, Ube 755-8611, P.O. Box 8611-755, Japan.

Abstract

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 digestive enzyme, 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.

Keywords