Difference and change rule of microbial community in the Qupi and Quxin of medium-high temperature Daqu during fermentation process

Medium-high temperature Daqu is an important source of microorganisms in the fermentation system of strong-flavor (Nongxiangxing) Baijiu. The difference and change rule of microbial community in Qupi (outer of daqu) and Quxin (interior of daqu) of medium-high temperature Daqu during fermentation process were analyzed by high-throughput sequencing technology combined with the determination of physicochemical indexes. The results showed that the moisture content, acidity and temperature of Quxin were higher than those of Qupi during fermentation process. Microbial diversity and richness index in Qupi were always higher than that in Quxin. The main dominant microbes in Qupi and Quxin were consistent, but the change rule of dominant microbes was quit different. Firmicutes, Actinobacteriota and Proteobacteria were the dominant bacterial phyla in Qupi and Quxin, and the relative abundance of Firmicutes in Qupi increased earlier than that in Quxin prior period of fermentation. Ascomycota, Basidiomycota and Mucoromycota were the dominant fungal phyla in Qupi and Quxin, and the relative abundance of Ascomycota in Quxin was slightly higher than that in Qupi during fermentation period. The main dominant bacterial genera in Qupi and Quxin were Thermoactinomyces, Lactobacillus and Saccharopolyspora. The relative abundance of Thermoactinomyces first increased and then decreased during Qupi fermentation, but it was opposite during Quxin fermentation period. The main dominant fungal genera were Saccharomycopsis, Thermomyces and Alternaria, and the relative abundance of Saccharomycopsis in Qupi increased faster than that in Quxin during fermentation period.