Dominant Microbes and Their Successions During Solid-State Fermentation of Luzhou-Flavour Liquor Based on High-Throughput Sequencing Following Culture

Microorganisms significantly affect the brewing process and product quality of liquors. The brewing process of traditional Chinese Luzhou-flavour liquor involves solid-state fermentation in an open environment with grains as the fermentation substrates and Daqu as the saccharifying fermenter. To identify the functional microbes in Luzhou-flavour liquor fermentation, the diversity and population succession of fungal and bacterial species were investigated using high-throughput sequencing (HTS) and a culture- dependent method. In total, 932 bacterial and 980 fungal operational taxonomic units (OTUs) were identified using HTS, and 256 bacterial and 130 yeast strains were isolated and identified using 16S rDNA, and 26S D1/D2 rDNA, and ITS v4/v5, respectively. Results of population succession determined using HTS showed that the dominant populations were yeasts, Lactobacillus, and Bacillus at the early stage, and yeasts and Lactobacillus in the late stage. Lactobacillus, Pichia, Bacillus, and Candida were abundant among all the three layers of fermented grains, indicating that they are the key dominant bacteria and yeasts. However, Candida ethanolica, Saccharomycete sp., and a non identified Saccharomyces cerevisiae were more abundant in the lower layer than in the middle and upper layers, and Lactobacillus parabuchneri, Oceanobacillus oncorhynchi, and Thermoactinomyces sp., were present only in the lower layer. Correlations between enzyme activity, volatile production, and dominant microbes during fermentation indicated that Pichia fermentans, Lactobacillus suebicus, Lactobacillus acetotolerans, Pichia kudriavzevii, Pichia exigua, and Bacillus tequilensis were significantly affected during brewing. These observations will assist in elucidating the mechanisms underlying Chinese Luzhou-flavour liquor production and in improving the quality and efficiency of traditional liquor brewing.