In this study, the microbial diversity of high temperature Daqu from different distilleries in Maotai town was analyzed by the pure culture technique and macrogenomic sequencing. The results showed that a total of 212 Bacillus strains were isolated and identified including B. sonorensis (77 strains), B. licheniformis (39 strains) and B. amyloliquefaciens (19 strains). A total of 55 high-quality genomes were obtained by metagenomic binning, including 18 new strains suspected of being Bacillus sp., Lactobacillus sp. and Weissella sp.. The analysis of the microflora structure showed that the dominant bacteria in Daqu were Desmospora sp. 8437, B. sonorensis and B. amyloliquefaciens, and the relative abundance of B. sonorensis and B. amyloliquefaciens in Daqu from distillery A were significantly lower than that from distillery B (P < 0.05). The diversity and abundance of microorganisms in high temperature Daqu from distillery A were significantly lower than those in Daqu from distillery B (P < 0.05), and there was a significant difference in microflora structure between them. In terms of functions, the differential metabolic pathways with higher abundance in high temperature Daqu from distillery A were mainly related to the biosynthesis of amino acids, while those from distillery B was mainly related to the degradation of L-rhamnose. This study is of positive significance for improving the fermentation process and screening excellent strains in the future.

In this study, multi-dimensional characterization of different layers of alcoholic fermentative material in Maotai-flavor baijiu cellar in the fifth round of fermentation from a certain region in Hubei was carried out by route analysis, culturable methods, metagenomics, and bionic methods. The results showed that there was no significant difference in the counts of total bacteria, lactic acid bacteria, or yeast and mold among different layers of alcoholic fermentative material (P > 0.05). However, acidity, alcohol content, starch content and reducing sugar content were significantly higher in the middle than lower layer (P < 0.05). Sensory evaluation showed that the lower layer had a stronger bitter taste and bitter aftertaste as well as higher concentrations of nitrogen oxides and methane. The analysis of sequencing data from the MG-RAST database for the fourth round of fermentation showed that the major genera in alcoholic fermentative material were Acetilactobacillus and Sarocladium, whose relative abundance in alcoholic fermentative material was significantly different between the fourth and fifth rounds of fermentation (P < 0.05). Also, there was a significant difference in the microbial community structure of alcoholic fermentative material between the two rounds (P < 0.05), while the difference in the microbial community structure among different layers of alcoholic fermentative material was relatively small. Correlation analysis showed that there was a close relationship between microorganisms in alcoholic fermentative material and its sensory and physicochemical quality.

The fungal community structure and flavor quality of white, yellow and black high-temperature Daqu from company A in Xiangyang, China were analyzed using MiSeq high-throughput sequencing and electronic nose technology. The sequencing results showed no significant differences in the α-diversity or β-diversity of fungal community among different colored Daqu (P > 0.05); the dominant fungal genera belonged to Ascomycota including Thermomyces (36.50%), Thermoascus (27.15%), Saccharomycopsis (9.23%) and Dipodascus (1.19%), and Mucoromycota including Aspergillus (9.36%), Rhizopus (1.44%) and Rhizomucor (1.03%). The electronic nose exhibited high sensor responses to volatile organic sulfides, terpenoids, hydroxides and ethanol and low sensor responses to aromatic substances in high-temperature Daqu; the Mann-Whitney test revealed significantly higher sensor responses to aromatic substances (P < 0.01) and lower sensor responses to the other aroma components (P < 0.05) in yellow than black Daqu. In addition, based on the fungal sequence data from the MG-RAST database for three different colored high-temperature Daqu produced by company B, comparative analysis of the fungal community structure of high-temperature Daqu produced by companies A and B was carried out. It was found that there were highly significant differences (P < 0.01) in the α-diversity and β-diversity of fungal community between Daqu produced by the two companies, and the results of cluster analysis showed that the Mahalanobis distance between the different colored high-temperature Daqu from the same company was closer. Finally, in this study, four strains of S. fibuligera were isolated from high-temperature Daqu produced by company A by traditional pure culture method. In conclusion, there was a significant difference between the fungal communities of high-temperature Daqu produced by companies A and B, which was greater than the difference between different colored high-temperature Daqu produced by the same company.