Organic acids, such as malic, succinic, and lactic acids, are crucial
factors in determining the taste of Japanese sake. The succinic and
malic acids produced by the yeast Saccharomyces cerevisiae during
sake fermentation confer an umami and a refreshing taste to the
sake, respectively (1). Because the majority of sake yeasts
predominantly produce succinic acid and relatively little malic acid,
yeast strain No. 28 has recently been developed to increase the
malic acid concentration in sake, and in so doing, to improve the
refreshing characteristics of the beverage (2). Yeast strain No. 28
was obtained from the parental strain K1001. Haploid cells of strain
K1001 were mutated by treatment with ethylmethane sulfonate to
produce the cycloheximide-resistant and high malic acidproducing
yeast strain CHp-18. Strain CHp-18 was then mated with
another sake yeast strain, strain KMI, and this cross was then
backcrossed with strain CHp-18. The resulting strain, which
exhibited high malic acid production, was named No. 28.