Characterization of the microbial community in different types of Daqu samples as revealed by 16S rRNA and 26S rRNA gene clone libraries

Daqu is a fermentative saccharification agent that is used to initiate fermentation in the production of Chinese liquor and vinegar. Different types of Daqu can be distinguished based on the maximum fermentation temperature, location of production, and raw materials used. We aimed to characterize and distinguish the different types of Daqu using a culture-independent cloning method. The lowest microbial diversity was found in Daqu produced at high-temperature. Principal component analysis (PCA) was used to compare the bacterial composition of Daqu from different regions (i.e., northern Daqu and southern Daqu). Staphylococcus gallinarum and Staphylococcus saprophyticus were found in southern Daqu, and were absent in northern Daqu. The fungi Saccharomycopsis fibuligera and Lichtheimia ramosa dominated in low/medium-temperature Daqu, whereas Thermomyces lanuginosus occurred in high-temperature Daqu. Our study identified potential biomarkers for the different types of Daqu, which can be useful for quality control and technology development of liquor or vinegar production.