Exploring the impacts of raw materials and environments on the microbiota in Chinese Daqu starter

Many traditional fermented foods and beverages in both eastern and western countries are produced with the addition of starter cultures. Daqu is the undefined starter used for Chinese liquor, which contributed many fermentation functional fungal and bacterial communities to liquor fermentation process. However, the sources of these microbial communities and how these microorganisms formed in Daqu are still unclear. In this study, high-throughput sequencing combined with microbial source tracking analysis were applied to analyze the sources of the microbial communities in Daqu. We found fungal communities in Daqu were mainly originated from Daqu making environments (mainly tools and indoor ground), including Saccharomycopsis fibuligera, Pichia kudriavzevii, Rhizopus oryzae, Sterigmatomyces elviae, Aspergillus flavus/oryzae, Hyphopichia burtonii and Lichtheimia corymbifera. Meanwhile, most of bacterial communities in Daqu were from raw materials, including Gammaproteobacteria, Alphaproteobacteria and Bacilli. During Daqu-making process, the abundance of Gammaproteobacteria and Alphaproteobacteria that were not beneficial to liquor fermentation declined, but the abundance of the fermentation functional yeasts and Bacilli increased. Moreover, network analysis showed the bacteria in Daqu might be the drivers for the microbial succession during the Daqu-making process. This study shows that the Daqu production technology is a good way to screen fermentation functional microorganisms from complex environmental microbial communities.