Study On Microbial Source Tracking And Seasonal Succession Of Shanxi Mature Vinegar With Liquid-Solid Fermentation Craft

Traditional Shanxi mature vinegar is brewed by combined fermentation of multiple strains in an open environment.The composition and succession of vinegar microbial community have been studied extensively by domestic and foreign scholars.However,the association mechanism between microbes in an open environment and vinegar brewing microbes is still unclear,and the influence of environmental changes caused by seasonal changes on the brewing microbial community structure needs further research.In this paper,the microorganism of traditional Shanxi vinegar brewing was studied,and the diversity and composition of microbial community of starter cultures,vinegar brewing environment samples,excipient bran and samples at different fermentation stages in different seasons were studied from the perspective of brewing microecology.On this basis,the fast expectation-maximization microbial source tracking(FEAST)method was used to analyze the contribution of starter cultures,workshop environmental microorganisms and excipient bran to vinegar brewing microorganisms.Finally,multivariate statistical analysis was used to conduct data mining on the diversity of microbial community composition in four seasons.The main conclusions are as follows:(1)Through analysis of high-throughput sequencing technology,bacterial OTUs in starter cultures,workshop environmental microbial samples,excipient bran and fermented Pei samples were higher than that of fungal OTUs,indicating that bacterial community diversity in starter cultures,workshop environmental microbial samples,excipient bran and fermented Pei samples was much higher than that of fungal community.According to the results of species annotation,the average relative abundance of seven bacteria genera and 15 fungi genera in starter cultures,workshop environmental microbial samples,excipient bran and fermented Pei samples were greater than 1%.FEAST results showed that bacterial communities were mainly from indoor ground,tool surface and Daqu on the second day of saccharification fermentation,while fungal communities were mainly from Daqu,air and Kuaiqu.At the end of alcoholic fermentation,wine Pei mixed with excipient bran and fermented grains and entered the acetic acid fermentation stage.Therefore,the bacterial communities in the samples on the first day of acetic acid fermentation were mainly from the tool surface,wine Pei on the 12 th day of alcoholic fermentation and air,while the fungal communities were mainly from the fermented grains,tool surface and air.(2)The results of high-throughput sequencing showed that the richness and diversity of bacterial community were different in the four seasons of fermentation.During the brewing process of Shanxi mature vinegar,there were more OTUs in summer and autumn samples than in spring and winter samples.Beta diversity analysis showed that 36 fermented Pei samples from nine different fermentation stages in four seasons were divided into four groups.Except for the samples from the first day of alcoholic fermentation in autumn,each group contained samples from different fermentation stages in the same season,and there were obvious differences among the samples from the same fermentation stage in different seasons.These results indicated that there were significant differences in bacterial community in different seasons and seasons had a greater impact on the composition of bacterial community than the fermentation stage in season.In addition,a total of 13 different bacteria were obtained from four seasonal fermentation samples,among which Leuconostoc and lactic acid bacteria(LAB)were the main genera that caused notable differences in bacterial community in different seasons.According to the results of species annotation,the average relative abundance of 12 bacterial genera detected in the fermentation samples in four seasons were greater than 1%,and there were seven highly connected bacterial genera in the interaction network composed of 12 bacterial genera,which may play an important role in steady-state fermentation of vinegar.(3)The richness and diversity of fungal community in Shanxi mature vinegar were different in the four seasons of fermentation,and the fungus OTUs in summer samples were more than that in other seasons.UPGMA results indicated that there were significant differences in fungal community in different seasons and seasons had a greater impact on the composition of fungal communitiy than the fermentation stage in season.In addition,a total of 18 fungi with significant differences were obtained from four seasonal samples.According to the species annotation results,the average relative abundance of 16 fungi genera detected in the four seasonal fermentation samples were greater than 1%,and the interaction network composed of these 16 fungi genera was dominated by positive correlation.Among them,Cladosporium,Alternaria,Epicoccum and Papiliotrema were significantly positively correlated with each other,and their relative abundance were similar in four seasons.This suggests that they have a common adaptation in the vinegar brewing environment,or form an interdependent and stable microbial community relationship.