Isolation and brewing properties of a sake yeast mutant with high ethyl caprylate productivity

Sake yeasts synthesize alcohols and other components, such as ethyl caproate, ethyl caprylate, and isoamyl acetate, which impart a unique and refined flavor profile to sake. In this study, a sake yeast mutant, K901C8, with high ethyl caprylate productivity was isolated from Kyokai no. 901 (K901), which has been passaged since 1993 at Yoshinogawa brewery, and its fermentative properties were investigated. This mutant was isolated from 960 antibiotic-resistant mutants obtained from 2.1× 107 cells with cerulenin as an inhibitor of fatty acid synthesis. In small-scale sake brewing experiments, the K901C8 mutant produced a high level of ethyl caprylate, which imparts a pineapple- and apricot-like flavor to sake. In the industrial-scale brewing, K901C8 showed fermentative properties similar to those of the wild-type K901, whereas K901C8 produced more ethyl caprylate than K901. These results demonstrate the potential of using K901C8 for producing high-quality sake with a novel flavor.