Isolation and characterization of a high-acetate-producing sake yeast Saccharomyces cerevisiae

The result of sensory evaluation of sake showed that acetic acid imparted desirable acidity when the proportion of acetic acid to lactic acid was about 1/3, even if the concentration of acetic acid was 0.75 g/l. Glycerol balanced the acidity and brought about a harmony between sweetness and acidity in sake. A high-acetate producing sake yeast (MHA-3) was isolated from mutants having low NADH dehydrogenase (NDE) activity. MHA-3 produced 15 times more acetate and 5 times more lactate than the parental strain Kyokai no. 901 (K-901) in a small-scale sake brewing test using 10 kg of rice. In addition, the concentrations of glycerol in sake brewed with MHA-3 were approximately 1.5-fold higher than in that brewed with K-901. The proportion of acetic acid to lactic acid was about 1/3 in sake fermented with MHA-3 and it exhibited a good balance between sweetness and acidity. The activities of glycerol-3-phosphate dehydrogenase (GPD) and aldehyde dehydrogenase (ALD) in MRA-3 were 1.4-fold and 3.1-fold, respectively, higher than those in K-901 while the activity of NDE was 40% that of K-901. MHA-3 accumulated higher amounts of acetate and glycerol than K-901 in static YNB10 medium. The concentrations of acetic acid produced, depending on the quantity of yeast cells added, increased in conjunction with increases in glycerol produced. We suggest that NDE might be linked with GPD and that the nde mutants, which can be used in sake brewing, produced higher amounts of acetate and glycerol.