Unraveling the composition and succession of microbial community and its relationship to flavor substances during Xin-flavor baijiu brewing

A novel baijiu type, Xin-flavor, has been developed via combining Qu and craftsmanship from three famous baijiu types including light-flavor, sauce-flavor, and strong-flavor. However, the microbial community and its relationship to physicochemical factors and flavor substances were little known during the three-stage brewing processes including saccharification, stacking, and fermentation. In this study, 21 phyla, 407 genera, and 615 species distributed in bacteria and fungi were identified via high-throughput sequencing (HTS). For bacterial community, the dominant bacteria at saccharification stage were Weissella and Leuconostoc, which were superseded by Acetobacter and Gluconobacter at stacking stage, then quickly replaced by Lactobacillus at fermentation stage. For fungal community, Rhizopus, dominant at saccharification stage, was partially replaced by Thermomyces at stacking stage, then was completely superseded by Thermoascus and three yeasts (Saccharomyces, Kazachstania and Apiotrichum) at fermentation stage. The moisture, ethanol, and acidity, as key factors affecting the microbial community, explained this microbial succession. Interestingly, Apiotrichum was firstly detected in fermented grains. Furthermore, the rapid accumulation of ethanol mainly occurred in the first 10 days of fermentation stage, and highly correlated with Saccharomyces, while Kazachstania and Apiotrichum were related to the formation of flavor substances (acetic acid, lactic acid, caproic acid, ethyl lactate and ethyl caproate). Therefore, this study provides fundamental basis for the rational control of baijiu production and improving the craft and quality of Xin-flavor baijiu.