Effect of kuratsuki Kocuria on sake brewing in different koji conditions

Abstract

Koji is made using steamed rice and a koji mold, which plays an essential role in sake brewing. We challenge to build a new sake brewing method using the kuratsuki bacteria that have inhabited each sake brewery. In this paper, effects of the kuratsuki Kocuria strain TGY1127_2 were estimated on sake brewing in different koji conditions. Sake was produced by incubation of a mixture solution of koji, water, and sake yeast (strain K1401) with and without the kuratsuki Kocuria TGY1127_2. The effects of the kuratsuki Kocuria on the taste of the sake differed among different koji. The kuratsuki Kocuria led to an increase in ethanol concentration. Additionally, the sugar content (Brix) and acidity of the sake increased in proportion to the amount of koji. These results strongly suggest that the kuratsuki Kocuria does not adversely affect the fermentation activity of the sake yeast. Thus, the kuratsuki Kocuria had different effects on the taste of sake among different koji but the fermentation activity of the sake yeast was maintained.