Association between flavors and microbial communities of traditional Aspergillus-Douchi produced by a typical industrial-scale factory

Abstract

Aspergillus-Douchi is a traditional fermentation food which possesses unique flavors caused by diverse microbiota in fermentation ecosystems. However, the correlations between flavor characteristics and microorganism succession are rarely researched. In this research, flavors and microorganism community (bacterial and fungal) of Douchi at different koji-making and post-fermentation stages were analyzed by SDE-GC-MS and 16S rRNA sequencing, respectively. Moreover, an association between flavor formation and microorganism succession was analyzed by Pearson analytical methods. Results showed that aldehydes, ketones and aromatic compounds were the primary flavors during koji-making. In the post-fermentation, the main flavors became acids, esters, aromatic compounds and alcohols, as well as many new elements, including hexadecenoic acid ethyl palmitate and 9,12-octadecadie methyl linoleate. In microorganism community, the dominant microorganisms were bacteria, including Bacillus velezensis, Bacillus licheniformis, Staphylococcus gallinarum, Staphylococcus saprophyticus and Pediococcus acidilactici. Aspergillaceae was only dominant fungal on the surface and inside Douchi throughout fermentation, with a relative abundance of over 40%. Bacillus velezensis were involved in synthesizing a wide variety of volatiles during koji-making, while Staphylococcus and Debaryomycetaceae were closely related to the flavor formation throughout post-fermentation. Conclusively, the aromatic flavors in Aspergillus-Douchi were mainly produced from the synergistic actions of bacteria (Bacillus and Staphylococcus) and fungi (Debaryomycetaceae).