Microbial Diversity In Traditional Solid-state Fermented Vinegar Daqu

Daqu is widely used in the brewing of traditional vinegar.It provides abundant biological enzymes and microorganisms for the brewing of vinegar.The quality of daqu is directly related to the yield and quality of vinegar.However,due to the limitations of traditional fermentation characteristics and research methods,people still have a limited understanding of the microbial community structure in the process of making daqu.In this paper,vinegar daqu was taken as the research object in fen town taiping brewery,xiangfen county,linfen city,Shanxi Province,and the traditional culture method and high-throughput sequencing method were combined to study the microbial community structure of daqu,so as to provide a scientific basis for exploring the functional microbial mechanism of vinegar daqu.The raw material and microorganism of daqu were isolated and identified by traditional culture method.A total of 205 strains were isolated and identified,including 108 fungi and 97 bacteria.The results showed that the dominant fungi in daqu included Lichtheimia ramosa,Lichtheimia corymbifera,Cladosporium subuliforme,and the dominant bacteria included Bacillus safensis and Bacillus pumilus.High-throughput sequencing was used to sequence bacterial 16 S r DNA V4 region and fungal ITS1 region,and the results were mainly analyzed as follows:(1)Alpha diversity analysis showed that microbial diversity in raw materials was higher than that in finished products,but for fungi,the abundance of fungal community in finished products was higher than that in raw materials.(2)Venn diagram analysis,species of daqu in the finished product and raw material samples of bacteria community OTU similarity degree is higher,moreover,the bacterial community in the finished product did not increase during the whole fermentation process,but was lower than the OTU numberin the raw material.On the contrary,the species similarity of fungi communities in Daqu products and raw materials is low,which may be due to the fact that fungi play a major role in the fermentation process of Daqu,and the proportion of dominant fungi is gradually increasing.(3)Community structure difference analysis: the composition of the bacterial community in the finished product was similar to that in the raw material,and the dominant bacterial genera were also very similar,both of which were bacillus and bacillus oceanic,but their abundance was different.The dominant fungi genera in daqu raw materials are Aspergillus,Monascus,Candida and Saccharomycopsis,while Saccharomycopsis in the finished products are more than those in the raw materials.The other three dominant fungi have a low proportion in the abundance value of the finished products.Saccharomycopsis has strong fermentation ability,high yield of alcohol and strong tolerance to ethanol,and is the most important functional strain in the brewing process.(4)Through comparative analysis of samples,it is easy to find that the bacterial community in finished products has a higher degree of aggregation,and the fungal community in raw materials has a higher degree of aggregation,indicating that the bacterial community of finished products is of high similarity,while the fungal community of raw materials is of high similarity.(5)The significance test of the difference between groups.For bacteria,the significant differences were shown in Pediococcus and Virgibacillus.For fungi,the differences were significant in Saccharomycopsis,Wallemia,Cephaliophora tropica.(6)ADONIS analysis showed that there were slight differences between the bacterial communities of finished products and raw materials(R2 =0.24217,P = 0.081).There was no significant difference between the fungal communities of raw materials and finished products(R2 = 0.14666,P =0.238).Comparing the two results,it was found that 23 genera identified bytraditional culture method appeared in high-throughput results,and the results of high-throughput method were richer than those of traditional culture method,but Paenibacillus cineris did not appear in high-throughput results.Therefore,the combination of culture and high-throughput method was used to estimate the overall microbial diversity.