9 - Microbiology of saké

Abstract

Saké is a traditional Japanese alcoholic drink produced from koji, rice, and water using alcohol fermentation of sake yeast. Koji is produced from koji mold and steamed rice. The koji mold converts rice starch into sugars, and the sake yeast converts sugars into ethanol. These conversions cooccur during sake brewing. Therefore, koji mold and saké yeast are essential for sake brewing. Furthermore, there are no studies on bacteria involved in sake brewing other than the lactic acid bacteria. Some lactic acid bacteria have positive effects on sake brewing, while some have adverse effects. Several recent studies showed that certain bacteria have lived in sake breweries and entered the sake production process every time. These bacteria are known as kuratsuki bacteria. We added the cultivated kuratsuki bacterium into the saké production process. The obtained sake product had a different flavor and taste when compared to the sake product obtained without adding the kuratsuki bacterium. Therefore, the function of kuratsuki bacteria during sake brewing and its effect on flavor and taste was examined. The diversity and function of the kuratsuki bacteria are uncertain. Nowadays, koji mold and saké yeast are commercially available. In contrast, kuratsuki bacteria have inhabited every sake brewery and are not commercially available. Microbiology involving sake and during sake production could reveal the diversity and function of kuratsuki bacteria. The research results contributed to establishing a unique method of saké brewing utilizing the kuratsuki bacteria. This method will help inherit and develop saké brewing in Japan.