Japanese sake is brewed by the saccharification of rice by
Aspergillus oryzae and simultaneous fermentation of glucose by the
sake yeast Saccharomyces cerevisiae (1). Because organic acids such
as succinic, lactic, malic and acetic acids that are mainly produced
by the sake yeast affect the taste of sake, the improvement of sake
based on the knowledge of its yeast-produced organic acid
composition has been pursued (2e5). In particular, malic acid
provides a refreshing taste, while acetic acid results in an undesirable
taste (6). Thus, analysis of the organic acid production
mechanism and breeding of new sake yeasts that provide different
organic acid combinations is required for the development of the
sake industry.