Abstract:Changes in the microbial community and differences in metabolites following the inoculation of a mixed fermentation system with Bacillus subtilis, the dominant species from Daqu, were investigated herein. High-throughput sequencing, HS-SPME-GC-MS, and PLS-DA were used to analyze the differences in microbial community structure and metabolism before and after inoculation, and Spearman correlation analysis was used to examine the correlation between the microorganisms and different flavor compounds. The results showed significant changes in the relative abundance of microorganisms after inoculation with B. subtilis, with the most significant changes being Bacillus decreasing from 76.56% to 0.04%, Enterobacter increasing from 0.01% to 71.53%, and Pichia decreasing from 62.17% to 12.89%. LEfSe analysis also revealed notable changes in the community structure after inoculation. The analysis of metabolites revealed significant differences before and after inoculation, with 19 metabolites, such as ethyl hexanoate, 2,3,5,6-tetramethylpyrazine, and ethyl acetate, being significantly different. Inoculation of Bacillus subtilis affected microbial changes, leading to variations in metabolites. Correlation analysis revealed that the changes in metabolites were related to the microorganisms with significant changes after inoculation. We found differences in community structure and metabolites in a mixed fermentation system after inoculation with B. subtilis and a correlation between the two, providing fundamental data for understanding the role of B. subtilis in a multispecies co-fermentation system.
