Correlation between microbial community succession and flavor substances during fermentation of Yongchuan Douchi

The microbial communities and flavor substances of Yongchuan Douchi (YCDC) have yet to be explored, and the lack of such knowledge has been challenging the industrial fermentation process of YCDC, impacting its taste quality. To bridge this gap and better understand the process, this study seeks to employ high-throughput sequencing to analyze the microbial community diversity of YCDC at different fermentation stages. The physicochemical properties, flavor substance compositions, and the relationships between microbial communities and major flavor substances were also explored in order to comprehend the knowledge gap. The results revealed a higher expression of bacterial genera diversity in comparison to fungal genera diversity. Throughout the fermentation process of YCDC, there was a gradual accumulation of free amino acids (Glutamic acid and Asparagine) and organic acids (Citric acid and Succinic acid). Additionally, we identified 29 major flavor substances with lipids, alcohols, aldehydes, and acids contributing significantly to the overall flavor profile. Staphylococcus spp, E. coli Shigella spp, and Puccinia spp were found having positive correlations with 1-octene-3-ol, ethyl isobutyrate, and benzaldehyde respectively, by this means imparting fruity and floral flavors to YCDC. Remarkably, the potential correlation of bacterial genera with flavor substances was observed to be higher than that of fungal genera. These findings add scientific knowledge into the succession of microbial communities in YCDC and serve as a theoretical reference for the screening and quality assessment of flavor bacteria.