Metagenomics Analysis Reveals Flavors Formation and Afb1 Metabolic Network of Doubanjiang-Meju Microbiota in Rotary Drum Fermenter of Varied Temperature

Abstract

The doubanjiang-meju was an important intermediate product for 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). The flavor substances and AFB1 in the two processes were determined in this study, and the metagenomics was applied to study the microbial diversity and explore the formation mechanisms of the key flavors and the degradation pathway of AFB1. The result indicated that compared with the FFCT, the FRDF showed higher contents of organic acids and free amino acids, and lower content of AFB1. 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. Staphylococcus gallinarum, unclassified_g__Staphylococcus and Pediococcus acidilactici showed higher abundances in the two processes by the analysis of metagenomics, identifying as the dominant microbes together with Tetragonococcus halophilus that appeared only in the FRDF, but the microorganisms in the FRDF presented more effective for the flavor formations and the AFB1 degradation. This study indicated the FRDF had the better performances than the FFCT.

Keywords: Doubanjiang-meju, Metagenomic analysis, Flavor substances, AFB1 degradation, Correlations, Metabolic network