Barcoded pyrosequencing analysis of the bacterial community of Daqu for light-flavour Chinese liquor

The bacterial community of Daqu affects its characteristics and functions by their metabolic products, such as amylase, protease, esterase. In this study, barcoded pyrosequencing was used to analyse the bacterial communities of three kinds of Daqu for light-flavour Chinese liquor brewing. A total of 13672 sequences were identified as bacterial sequences. The Shannon index of QC, HX and GT for clusters sharing 97% homology was 5·0, 4·2 and 4·2, respectively, indicating that QC had the highest biodiversity. The Good's coverage index of QC, HX and GT was 88·2, 93·4 and 93%, respectively, indicating that the vast majority of phylotypes have been detected. Among the three kinds of Daqu, the majority of annotated reads were assigned to two phyla (Firmicutes and Actinobacteria). The phylum Firmicutes was the most abundant group in QC (74·2%), HX (81·4%) and GT (98·6%), and the phylum Actinobacteria was the second in QC (23·9%), HX (17·9%) and GT (1·1%). There were many lactic acid bacteria in all three kinds of Daqu QC (45·8%), HX (46·3%) and GT (24·7%). In addition, the most abundant family in GT was Bacillus, accounting for 65·0%, while in HX, the families Thermoactinomycetaceae and Streptomycetaceae accounted for 19·5 and 14·1%, respectively, and in QC, 13·1% were Streptomycetaceae, 12·2% were heterofermentative Leuconostocaceae.

Significance and impact of the study: There are three kinds of Daqu (starter material) used for famous Chinese light-flavour liquor brewing, that is Qingcha, Hongxin and Houhuo. Since Daqu was fermented in an open environment, the microbiology communities were different with different kind of Daqu. Objective bacterial communities determined by barcoded pyrosequencing help to speculate possible metabolic productions, even to guess the function of many kind of Daqu in light-flavour liquor brewing.