Metagenomics analysis reveals flavors formation and AFB1 metabolic network of doubanjiang-meju microbiota in rotary drum fermenter of Unsteady Temperature Field

The doubanjiang-meju was an important intermediate product for Pixian Douban (PXDB) production. In this study, the fermentation in rotary drum fermenter (FRDF) for doubanjiang-meju was studied by comparing with the fermentation in the fermenter of constant temperature (FFCT). Compared with the FFCT, the FRDF showed higher contents of organic acids and free amino acids, and lower content of aflatoxin B 1 (AFB 1 ). The largest quantity of detected volatiles was 87 in the FRDF but 78 in the FFCT. Six key aromas in the FRDF showed stronger odor activities than those in the FFCT, and one key aroma 2,6-dimethylpyrazine appeared only in the FRDF. The core microbes were the same in the two processes except that Tetragonococcus halophilus appeared only in the FRDF, but the microorganisms in the FRDF presented more effective for the flavor formations and the AFB 1 degradation. The results indicated the FRDF had the better performances than the FFCT. • Rotary drum fermenter in unsteady temperature field was built to ferment doubanjiang-meju. • Tetragonococcus halophilus appeared only in the process of rotary drum fermenter. • A key aroma 2,6-dimethylpyrazine appeared only in the rotary drum fermenter process • The pathways for the key flavor formation and the AFB 1 degradation were clarified. • The quality of doubanjiang-meju was better in the rotary drum fermenter process.