Unraveling the correlations between bacterial diversity, physicochemical properties and bacterial community succession during the fermentation of traditional Chinese strong-flavor Daqu

Daqu provides a complex and unique microbial ecosystem and acts as a fermentation starter and a source of flavor compounds for Chinese strong-flavor Baijiu production. Dynamic changes in Daqu bacterial composition and physicochemical properties during production were studied using physicochemical analysis and Illumina HiSeq sequencing, revealing that the bacterial α- and β-diversity changed markedly after the start of fermentation. The dominant bacterial genera were Cyanobacteria, Proteobacteria and Firmicutes; Enterobacter, within Proteobacteria, was at the most influential node of the interaction network, and was positively correlated with Bacillus, Pantoea and Pediococcus. Redundancy analysis showed that the bacterial community structure was closely related to the physicochemical properties of Daqu, especially the acidity, cellulase activity and moisture. These findings clarified the complex bacterial community succession and interactions between organisms and with physicochemical properties, during Daqu fermentation, thereby enabling quality improvement of strong-flavor Baijiu, by augmenting selected bacterial cultures, or by controlling environmental factors.