Revealing the functional microbiota for acetic acid formation in Daqu starter for Chinese Nong-Xiang Baijiu fermentation

Abstract

High content of ethyl acetate may destroy the typical flavor of Chinese Nong-xiang Baijiu. Formation of ethyl acetate is closely related to its precursor acetic acid from Daqu starter in the fermentation process of Chinese Baijiu. In this study, the potential functional microbiota responsible for production of acetic acid was explored by correlation analysis and function prediction in Nong-xiang Daqu from different geographical regions. Our results revealed that the microbial community of Daqu starter was correlated with its acetic acid content. In addition, the relative abundances of Weissella, Lactobacillus, Bacillus, Kroppenstedtia, and Pichia were higher in the Daqu with high content of acetic acid. Furthermore, Acetobacter, Weissella, Lactobacillus, Pichia, Candida, and Rhizomucor were significantly (p < 0.01) and positively correlated with acetic acid. Meanwhile, higher abundances of most genes that encoding enzymes participated in glycolysis and pentose phosphate pathways for acetic acid synthesis, were observed by PICRUSt2 approach in the Daqu starters with high content of acetic acid. Taken together, Acetobacter, Weissella, Lactobacillus, Pichia, and Candida were determined as the potential functional microbiota for producing acetic acid in Nong-xiang Daqu starters. These results provided evidence of microbiota for revealing the possible causes of high acetic acid and ethyl acetate in Nong-xiang Baijiu brewing process, and laid theoretical foundation for regulation of Baijiu fermentation by functional microbiota.