Abstract: In the present study, we used metatranscriptomics to comparatively analyze the structure and function of the living bacterial community in naturally fermented soybean paste in the early and late stages of fermentation. We established that the purity and yield of extracted RNA could be increased by discarding the supernatant after centrifugation at 8 000 r/min for 5 min at 4 ℃ in the sample pretreatment procedure. High-throughput sequencing results showed that bacteria played a leading role in the fermentation of soybean paste, with the dominant genera being Tetragenococcus and Lactobacillus. Fungi were abundant only in the early stage of fermentation, and their abundance was low at the end of fermentation. The function of the bacterial community was mainly concentrated on the metabolism of carbohydrates and amino acids, and most of them were enriched at the end of fermentation. The results at the species and functional levels were consistent with each other. In summary, this study provides a new method and technical support for selecting excellent strains for the fermentation of soybean paste and for identifying the microorganisms that really play a role in the fermentation process.

Key words: metatranscriptomics, soybean paste, viable bacteria, microbial community structure, functional annotation