2021 Volume 62 Issue 2 Pages 65-75
To develop a new type of sake with a unique characteristic flavor, wild yeast strains were isolated from plants. Following genetic analysis using the 26S rDNA D1/D2 and ITS1-5.8S rDNA-ITS2 regions, six of the 44 isolated strains were identified as Saccharomyces cerevisiae. The results of genetic analyses and physiological tests of the six strains suggested that four strains, namely NKY32, NKY362, NKY392, and NKY2024, were types of sake yeast; the other strains, NKY1488 and NKY1945, were different from sake yeast. In small-scale sake brewing tests, the alcohol fermentation ability of the six strains was found to be approximately equal to that of the sake yeast K701. Sake brewed with NKY1488 and NKY1945 was different in that it exhibited high acidity, low amino acidity, and high acetic acid concentrations. These results indicate the usefulness of the six strains for brewing sake. Moreover, NKY1488 and NKY1945 demonstrated unique brewing characteristics. In a pilot-scale sake brewing test with NKY1488, a delay in alcoholic fermentation in the early stages was not observed and the sake could be brewed by the normal method. The brewed sake had a distinctive organic acid composition and was evaluated as a unique sake with a characteristic floral and spicy aroma and sour taste. These results demonstrate that NKY1488 can be used for brewing sake.
