Abstract: In this study, microbial proteins were extracted by Tris/phenol extraction-methanol/ammonium acetate precipitation from fermented grains for nongxiangxing baijiu production pretreated by centrifugation-ultrasonic disruption (C-UD) or liquid nitrogen grinding-ultrasonic disruption (LNG-UD) and the structure of the microbial communities obtained by the two pretreatment methods was evaluated by using label-free quantitative proteomics. The results showed that there was no significant difference between the protein contents extracted by both pretreatment methods. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the C-UD extract contained more and clearer protein bands. The number of identified peptides and proteins obtained by C-UD was higher than that obtained by LNG-UD, and the Score Sequest HT of protein identification was higher. The microbial species and community structure obtained by the two pretreatment methods were significantly different, and both were significantly different from the results obtained by genomic amplicon sequencing for the same samples, implying the importance of multi-omic designs for studying the microbial community in fermented grains. The results of the present study will help to optimize the extraction of microbial proteins from fermented grains for baijiu production, and lay a foundation for further understanding baijiu fermentation and improving baijing quality.

Key words: baijiu; metaproteomics; metagenomics; microbial community; fermented grains for baijiu production; pretreatment method