Regulating fermentation based on dominant genus: Effects of phenethyl alcohol-producing Saccharomyces cerevisiae on microbial succession and flavor compounds in fermented grains

Fortified inoculation with functional strains can improve and enhance the quality of fermented grains(FG) during Baijiu brewing and influence the flavor of the base Baijiu, but the underlying mechanisms remain unclear due to the lack of a comprehensive understanding of the complex and dynamic processes in the fermentation system. In this study, we screened a high-yielding phenethyl alcohol Saccharomyces cerevisiae from FG and investigated the perturbing effects of its enrichment on the physicochemical properties, microbial communities and volatiles of the fermentation process in FG. Microbial diversity showed that the microbial community structure of FG was markedly bioturbated, with an increase in the abundance of Saccharomyces at the genus level, and that the biomarkers in the fortified group on day 15 of fermentation were Pediococcus and Saccharomyces, and those in the control group were Weissella and Saccharomycopsis. The complexity and tightness of the correlation network was increased in the fortified group, and the correlation of Saccharomyces with LAB family microorganisms shifted from Lactobacillus to Pediococcus. Mantel test and linear regression analyses indicated that acidity and pH drove microbial community succession. Phenethyl alcohol content and quality of FG and base Baijiu were improved after fortification, and PICRUSt2 predicted that aryl alcohol dehydrogenase, a key enzyme in the phenethyl alcohol synthesis pathway, was more highly expressed in the fortified group. These results elucidate the potential mechanisms by which functional strains of dominant genera regulate communities and metabolism, and provide a theoretical basis for targeted regulation of fermentation of FG in Baijiu brewing.