Microbial Diversity in Daqu during Production of Luzhou Flavored Liquor

Yeast, bacterial, and mold strains in different stages during the daqubased production of Luzhou-flavored liquor were isolated and identified by analyzing the 26S rRNA, 16S rRNA, and internal transcribed spacer region sequences, respectively. In total, 113 yeast, 63 bacteria, and 128 mold strains were identified, with the majority identified to the species level and the remaining strains identified to the genus level. In the final daqu product (day 90), the dominant bacteria, yeast, and mold strains were Bacillus subtilis subsp. inaquosorum, Saccharomycopsis fibuligera, and Lichtheimia ramosa, respectively. Thus, in the finished product, the daqu microflora mainly comprised bacteria and molds, mostly consisting of heat-resistant spore-forming Bacillus spp. and filamentous fungi. Corresponding changes in the enzyme activity patterns during daqu production revealed that Mucor circinelloides f. circinelloides was strongly correlated with protease, whereas saccharifying enzyme activity was mainly correlated with Rhizopus oryzae. A relatively strong correlation was found between saccharifying and liquefied enzyme activities and Staphylococcus saprophyticus subsp. saprophyticus, Bacillus tequilensis, Weissella cibaria, and Enterobacter mori. These results indicate the benefits of molecular methods for detailed microbial isolation and identification and provide basic information for subsequent studies to reveal the functional microorganisms of daqu during the production of Luzhou-flavored liquor.