Kuratsuki Bacteria Interactions with Sake Yeast and Effect on Taste

Various microorganisms, referred to as kuratsuki microorganisms, inhabit each sake brewery. Previously, kuratsuki yeasts had been used for sake production in each sake brewery. Kuratsuki lactic acid bacteria have been used to produce kimoto, a fermentation starter. Kuratsuki non-lactic acid bacteria were examined to evaluate their potential roles and effects in sake production. The addition of kuratsuki bacteria to the sake-making process can change the flavor and taste of the sake. This change was observed in both the coculture experiments between sake yeast and kuratsuki bacteria and the sake making tests with and without kuratsuki bacteria. The comprehensive gene expression analysis of sake yeast cocultured with kuratsuki bacteria showed that 1.2% of the yeast genes were upregulated and 1.0% were downregulated following the addition of kuratsuki bacteria. This indicates that the change in flavor and taste of sake due to the addition of kuratsuki bacteria was caused by the interaction between sake yeast and kuratsuki bacteria. To understand the implications of kuratsuki bacteria in sake production, it is essential to study the interactions between sake yeast and kuratsuki bacteria.