Comparative analysis of microbial communities and flavor compounds in multi-round fermented grains of Jiang-flavor Baijiu from riverside and mountain locations.

Geographic location is increasingly recognized as a key factor shaping microbial communities and flavor formation in traditional fermented foods. However, its impact on the multi-round fermentation process of Jiang-flavor Baijiu remains poorly understood. This study systematically compared the physicochemical characteristics, volatile flavor compounds, and microbial community dynamics of jiupei from riverside (RS) and mountain (MS) locations within the Chishui River basin across six consecutive fermentation rounds (R1-R6). The results showed that location-associated effects on flavor accumulation became more pronounced during mid-rounds (R3-R4), with RS exhibiting higher total relative content of volatile flavor compounds than MS. Bacterial communities were dominated by Kroppenstedtia, Lentibacillus, and Bacillus during heaped fermentation, whereas Acetilactobacillus prevailed in pit fermentation. Dominant fungal genera included Saccharomycopsis, Thermomyces, Zygosaccharomyces, and Saccharomyces. Stochastic processes dominated both bacterial and fungal community assembly across all rounds and locations. PERMANOVA revealed that geographic location significantly affected fungal community structure but not bacterial community structure. LEfSe and random forest analyses identified distinct location-associated biomarkers: Aspergillus was enriched in RS, whereas Kroppenstedtia and Lentibacillus were enriched in MS. Despite these differences, both locations shared highly similar core microbiota (seven bacterial and four fungal genera) and conserved microbiota-flavor correlation networks. Network analysis further revealed that keystone species differed markedly between the two locations. Four bacterial keystone species were identified in MS but none in RS, whereas five fungal keystone species were identified in RS but only one in MS. This study provides new insights into the microbial terroir of Jiang-flavor Baijiu and has practical implications for quality control and flavor optimization across production locations.