Investigation into spatial profile of microbial community dynamics and flavor metabolites during the bioaugmented solid-state fermentation of Baijiu
Biofortification of baijiu fermentation using exogenous functional strains can change the microbial community structure of the fermentation ecosystem and flavor metabolism, which can impact Baijiu flavor. In this work, a high ethyl hexanoate-producing Saccharomyces cerevisiae Y285 strain was added to investigate microbial communities' succession and flavor compounds throughout the fermentation of Baijiu. The microbial community composition of the fermentation samples was analyzed using the Illumina MiSeq platform, and the results showed that Pediococcus, Lactobacillus, Weissella and Saccharomyces were the dominant genera. A total of 111 flavor compounds, esters (50), alcohols (14), acids (3), aldehydes (9), phenols (9), pyrazines (3), ketones (8), and others (15), were detected in all samples, and the content of total esters of the fortified Daqu increased dramatically. Among them, the content of ethyl hexanoate increased significantly, while the content of ethyl acetate decreased, and the content of other compounds such as ethyl palmitate, ethanol, phenethyl alcohol and tetramethylpyrazine also increased. Redundancy analysis (RDA) and Spearman's correlation analysis showed that Saccharomyces, Pediococcus, Lactobacillus, and Weissella were significantly positively correlated with esters and alcohols. To summarize, biofortification with S. cerevisiae during Baijiu fermentation modifies microbial community composition, as well as the content of ethyl hexanoate in Baijiu, and induces changes in the content of other flavor compounds. These findings imply that modifying the microorganisms throughout the baijiu fermentation process can alter the flavor of Baijiu and enhance it further.