Breeding of New Saccharomyces cerevisiae Hybrids with Reduced Higher Alcohol Production for Light-Aroma-Type-Xiaoqu Baijiu Production

Abstract

Baijiu, also referred to as "Chinese liquor", is a traditional spirit that originated in China over 2000 years ago and is the world’s bestselling liquor today. It is produced using a solid-state fermentation process, often using sorghum as raw material, in which a complex microbial cocktail (called "Jiuqu") is introduced to initiate the fermentation process. During fermentation, a plethora of flavor-active metabolites is produced by microbes. Depending on the flavors formed, Baijiu can be subdivided into sauce-aroma-type, strong-aroma-type, and light-aroma-type. A key feature of light-aroma-type Xiaoqu Baijiu (LATXB) is its relatively low concentration of higher alcohols (HA). However, reaching sufficiently low HA concentrations without affecting the overall taste and flavor of LATXB is often difficult. In this project, breeding was used to develop a new Saccharomyces cerevisiae hybrid strain for LATXB production, which shows reduced HA production. This strain, dubbed “hybrid 5”, reduced total HA by 10.3%, without compromising the production of other metabolites or fermentation efficiency when evaluated at an industrial scale (2 tons). Together, these results show the potential of breeding to produce superior, non-GM yeasts that are directly applicable for commercial Baijiu production.