Dynamics of microbial community structure and enzyme activities during the solid-state fermentation of Forgood Daqu: a starter of Chinese strong flavour Baijiu.

Daqu is the traditional fermentation starter for Chinese Baijiu, a traditional Chinese distilled liquor. Although the microbes in Daqu blocks play important roles in the solid-state fermentation process, the changes in microbial community structure and the correlation between the microbiota and enzyme activity have seldom been discussed in previous studies. In this research, a high-throughput Illumina MiSeq sequencing method was used to detect the compositions and changes in microbial diversity in Daqu blocks. The results showed that high-temperature solid fermentation directly changed the main microorganisms from Saccharomycopsis, Wickerhamomyces, Bacillus and Staphylococcus to Aspergillus, Thermoascus, Thermoactinomyces and an unspecified Thermoactinomycetaceae. The richness and diversity of both fungi and bacteria showed a tendency to first increase and then decrease. Through redundancy analysis, it was found that there were positive correlations between certain enzyme activities and certain microbes. (1) Glucoamylase and esterase activities correlated with abundances of Leuconostoc, Weissella, an unspecified Aspergillaceae, an unspecified Trichosporonaceae and an unspecified Ascomycota. (2) Amylase activity correlated with abundances of an unspecified Thermoactinomycetaceae, Thermoactinomyces, Aspergillus and Rasamsonia. (3) Protease activity correlated with abundances of Bacillus, an unspecified Lactobacillus and Saccharomycopsis. In summary, the results of this research provide useful information for understanding and controlling the maturation process of Daqu.