2020 Volume 36 Issue 2 Pages 25-37
Kokushu (sake, shochu, and awamori), an alcohol of Japanese origin, is traditionally brewed from rice and other materials. It is brewed by saccharification of koji and alcoholic fermentation of yeast. Since the 19th century, many strains of yeast have been isolated and studied taxonomically for kokushu brewing. Since the book “The yeasts, a taxonomic study” was published in 1952, all the original names assigned to these yeast strains are the synonym of Saccharomyces cerevisiae. Nonetheless, kokushu can be fermented exclusively by specific kokushu yeast strains. To confirm this, 96yeast strains were collected, taxonomically characterized, and used for comparison with other strains of the genus Saccharomyces. Then, seven tests were performed as described as “Key to species” of the book “The yeasts, a taxonomic study (5th ed.)” most of the kokushu yeast strains formed a homogeneous cluster and were separated from other species of the genus Saccharomyces. Of the 96 kokushu yeast strains that were studied and grown on vitamin-free medium, growth difference from Saccharomyces cerevisiae was observed in 90 strains. These results showed that kokushu yeast strains are unique in their phenotypic characteristics; thus, more information can be obtained from these strains for taxonomic studies on genomics and selection of yeast strains possessing specificity for kokushu brewing.
