Abstract: The Illumina HiSeq 2500 sequencing system was used to perform a comprehensive analysis of the dynamics of bacterial community structure during the high-temperature Daqu making process and the fermentation process of Maotai-flavor liquor. The experimental results showed that the population and community structure of the microflora were diverse for both processes and the bacterial species compositions were basically the same. The dominant bacterial phyla were Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes for both process. The ecological environment was different between the two processes, resulting in variability in the dominant bacterial community composition. In addition, the bacterial community regularly changed during the fermentation process of Maotai-flavor liquor. The change in the bacterial community in Daqu was related to storage time. The predominant genera in Daqu were Clostridium sensu stricto 1, Escherichia-Shigella, Lactobacillus, Streptococcus, Actinobacillus, Bifidobacterium, Peptoclostridium, Mycoplasma and Citrobacter. The abundance of Escherichia-Shigella, Actinobacillus, Bifidobacterium and Citrobacter increased with increasing storage time, the abundance of Clostridium sensu stricto 1 and Mycoplasma first increased and then decreased, the abundance of Lactobacillus and Peptoclostridium did not obviously change, and the abundance of Streptococcus showed a downward tendency. The bacterial community in fermented grains changed from pit fermentation to high-temperature stacking fermentation. The dominant?microorganisms during the liquor fermentation process were Escherichia-Shigella, Lactobacillus, Clostridium sensu stricto 1, Streptococcus, Actinobacillus, Bifidobacterium and Alternaria. The numbers of Escherichia-Shigella and Lactobacillus, having higher relative abundance, increased during the early fermentation period, then decreased from the second round until reaching a minimum at the high-temperature stacking fermentation stage of the third round, and finally increased gradually again during the late fermentation stage. The abundance of Clostridium sensu stricto 1 and Streptococcus decreased first and then increased. Taken together, our results revealed that the dominant genera during the high-temperature Daqu making process and the liquor fermentation process were basically the same, which indicates that Daqu is the microbial source for the fermentation of fermented?grains. In addition, the growth tolerance of bacteria was strong. As time went on, the variations of temperature and water reached an equilibrium, and the bacterial community was gradually dominated by a single species, which is more conducive for the brewing of Maotai-flavor liquor.

Key words: Maotai-flavor liquor, Daqu, fermented grains, bacteria, high throughput sequencing