Kuratsuki bacteria: overlooked supporting players in sake making

Abstract

  The main players in sake making are koji mold and sake yeast, with koji mold’s main role being starch saccharification, and sake yeast’s main role being ethanol fermentation. However, there are supporting players in sake making that have been overlooked. These supporting players are kuratsuki bacteria, which change the role of sake yeast through interactions with sake yeast, thereby changing the flavor and taste of sake. While sake yeast, the main player, is used all over the country, the kuratsuki bacteria play a role in each sake brewery, and the role of each varies from brewery to brewery. We have isolated, identified, and analyzed the functions of the kuratsuki bacteria to clarify their role. Kuratsuki bacteria do not inhibit the activity of sake yeast. By considering the interactions between sake yeast and kuratsuki bacteria during sake making, it may become possible to make sake in a way that has never been seen before.