Analysis Of Microbial Community Structure Characteristics Of Maotai-flavor Liquor Cellar Fermented Grains In Maotai Production Area

Maotai-flavor Baijiu has a long history of fermentation,and its unique technology has created a complex and special microbial community structure,which ultimately forms the unique style of Maotai-flavor Baijiu.It is produced by spontaneous fermentation processes in the open environment involving complex microbiota,which can be divided into three stages,namely Daqu(starter)preparation,stacking fermentation,and alcohol fermentation.Among them,alcohol fermentation is the process of converting sugar into alcohol and then producing aroma.Its high-temperature is conducive to the progress of biochemical effects such as Maillard reaction,promotes the fermentation and aromatization,and can effectively inhibit the propagation of pathogenic bacteria at the same time.The loss of metabolic activities of microorganisms such as ester-producing yeasts,caproic acid bacteria and other microorganisms provides a sufficient carbon source.Moreover,its fermentation time accounts for more than half of the entire production cycle.It can be seen that the microbial structure during the alcohol fermentation process is important to the entire ferment system and flavor formation of Maotai-flavor Baijiu.In this study,high-throughput sequencing technology was used to systematically analyze the microbial community structure in alcohol fermented grains in four Baijiu-producing areas in Maotai town.Combining mathematical statistics softwares to analyze the biological relationship between dominant microorganisms,The main results are as follows:(1)A total of 10 fungal phyla,371 fungal genera,42 bacterial phyla,and 1044 bacterial genera were detected in the entire fermentation cycle(seven rounds)of alcohol fermented grains in the four fermentation areas of Maotai town.In the seven rounds,there were 4common dominant fungal phyla,50 common dominant fungal genera,13 common dominant bacteria phyla,86 common dominant bacterial genera.At the phylum level and the genus level,the common microorganisms in different fermentation rounds occupied an absolute dominant position(91.00%-99.00%).There were endemic genera in each round,and the species were richer,but the relative abundance and proportion of endemic genera in each round was below 0.40%.There were 2 common dominant fungal phyla,1 dominant bacteria phylum in different rounds,namely Ascomycota,Basidiomycota and Firmicutes.5 bacterial phyla were detected for the first time in Chinese Baijiu fermented grains,including Margulisbacteria,Elusimicrobia,Candidatus?Gracilibacteria,Entotheonellaeota and Atribacteria.The common dominant fungal genera were Saccharomyces and Thermoascus,and the common dominant bacterial genera Lactobacillus was the absolute dominant bacterial genera.The proportion of each round was 61.92%-98.06%.(2)In the four areas of Maotai town,there were 5 common dominant fungal phyla,85 common dominant fungal genera,19 common dominant bacterial phyla,and 257 common dominant bacterial genera in total.At the phylum level and the genus level,the common microorganisms in different areas has reached more than 99.00%.The number of unique dominant fungal genera in the alcohol fermented grains from Area1-Area4 were 30,52,43 and 30,and the number of unique dominant bacterial genera were 84,68,140 and 96.Although the species of unique genera in each area were abundant,their relative abundance and proportion were relatively small(0.04%-0.19%).There were 4 dominant phyla in different fermentation rounds,namely Ascomycota,Basidiomycota,Firmicutes and Proteobacteria.There were 8 dominant fungal genera including Zygosaccharomyces,Saccharomyces,Schizosaccharomyces and Monascus.Lactobacillus and Stenotrophomonas were common dominant bacterial genera in the Area1-Area4.(3)Through the analysis of the differences between the Alpha diversity,the differences in the microbial diversity of the alcohol fermented grains in each round were more significant.By calculating the Spearman's rank correlation coefficients among the dominant genera in different rounds to analyze the correlation,we found that there were 18 dominant fungal genera and 8 dominant bacterial genera that had significant correlations.Among them,There was a significant negative correlation between the two dominant fungal genera,including Saccharomyces and Zygosaccharomyces,Monascus,Penicillium,Eupenicillium,etc.Lactobacillus has significant negative correlation with 6 genera,including Stenotrophomonas,Bacillus and Acinetobacter,etc.There were positive correlation between other dominant bacterial genera,such as Acinetobacter and Sphingomonas,Weissella,Aeromonas,etc.(4)There were differences in the microbial Alpha diversity of the alcohol fermented grains samples from different areas.Among them,the fungi in Area1 and Area2 were significantly different,and the bacteria in Area2 and Area3 were significantly different.From the Spearman's rank correlation coefficients among the dominant genera in different areas,we found that there were 15 dominant fungal genera that had significant correlations.Among them,Thermoascus and Thermomyces,Talaromyces showed significant positive correlation,Saccharomyces and Zygosaccharomyces,Penicillium and other 8 groups of dominant fungal genera had a significant negative correlation.The correlation between the 9 dominant bacterial genera was significant,among which,Lactobacillus has a significant negative correlation with 7 dominant bacterial genera.Kroppenstedtia,Bacillus,Acinetobacter,Sphingomonas,Virgibacillus,Weissella showed a significant positive correlation with each other.