Analysis Of Bacterial Community And Screened Of Enhancing Flavor Bacillus In Daqu Of Northern

The microbial community of Jiang-flavor Daqu in north was analyzed by high-throughput sequencing,and the changes of bacterial community in Daqu were investigated by high-throughput sequencing.The results showed that the bacterial community structure of Daqu was in dynamic change during different fermentation periods.With the fermentation of Daqu mature and stable,the diversity of bacterial community structure tended to be stable,and dominant strains gradually appeared.There were 194 and 234 species separated from white Daqu and yellow Daqu respectively,which contained 174 identical species.Further study,the dominant genus were separated respectively from white Daqu and yellow Daqu white.The dominant genus of white Daqu was Thermoactinomyces,the content was 49.78%,and the genus with the highest relative abundance was Lentibacillus,the content was 70.98%.Bacillus is the genus of the highest relative abundance in Daqu,so this paper selected Bacillus as the starting point to study the strains,which possessed characteristics of flavor enhancement.After that according to the size of protease clear circle and v-p chromogenic test of precursor ACT and product enzyme were used to screen the dominant strains.It was important to screen a functional Bacillus of high-yield TTMP.The results showed that inoculated functional strain could produce TTMP 550.85±68.73 on YPG fermentation medium;could produce 23.19±5.43 mg/L on solid fermentation medium.On the basis of molecular biological techniques and physiological and biochemical tests of spore bacteria,the strain of high-yield TTMP and enhance flavor was identified from Daqu,it belonged to Bacillus,named Bacillus amyloliquefaciens DQBC-3,the strain can simultaneously produce specific enzymes such as amylase,protease,cellulase,xylanase,Pectinase,coagulase and so on.The bacteria in high temperature fermentation environment enhanced Jiang-flavor ability of Daqu;enhanced flavor substances and the content of TTMP in Jiang-flavor liquor.In this study,analyzed the microbes community structure of Jiang-flavor Daqu samples based on Illumina Mi Seq platform sequencing method,and analyzed the microbial community composition and differences between ordinary Daqu and enhanced Daqu.Among bacteria,the relative abundance of Lentibacillus increased from 3.56% to 8.39% and that of Bacillus increased from 0.91% to 42.33% after inoculated functional strain.The results showed that bacillus added to Daqu could not only fine-regulate the microbial community in Daqu,but also secreted a large number of enzymes and improve the hydrolase system,such as amylase and glucose amylase.Activity of saccharifying enzyme was 851.81±23.56 U/g,neutral protease was 79.05±6.57 U/g,acid protease was 92.65±10.27 U/g,enzyme activity of liquefied enzyme was 36.5±7.58 U/g,cellulase activity was 2.38±0.18 U/g,pectinase activity was 262.94±39.62 U/g,lipase activity was 12.77±1.53 U/g;Compared with ordinary Daqu,saccharifying enzymes increased by 1.45,neutral protease and acid protease increased respectively 1.31 and 0.54,and liquefaction enzymes,cellulase,pectinase and lipase increased respectively 0.58,0.78,0.68 and 0.43.GC-MS was used to analyze the differences of flavor compounds between the two groups.The results showed that 40 kinds of volatile flavor substances were detected in the enhanced Daqu,which formed Daqu with mixed aroma.Including nine kinds of alcohols,five kinds of acids,twelve kinds of esters,five kinds of ketones,four kinds of pyrazine,two kinds of furan and 2 kinds of phenol,especially ester compounds were the highest content of many compounds,achieve better than 46.98%,these esters with ethyl acetate,ethyl methyl benzoic acid,hexadecanoic acid,formic acid isopropyl ester,ethyl caproate as the main body fragrance;Alcohol,acids,aldehydes and esters were all indispensable components in liquor and played an important role in liquor flavor.On the other hand,analyzed to detect the functional pyrazine compounds from fortified Daqu,The relative amounts of pyrazine in strengthened daqu and ordinary daqu were 5.30% and 1.69% respectively,which increased by 2.13 times these compounds had strong roasted nuts,Jiang-flavor,bread burnt and smoky aromas.The main volatile components of ordinary Jiang-flavor Daqu were significantly less than the types and relative contents of fortified Daqu,included eight kinds of alcohols,four kinds of acids,ten kinds of esters,five kinds of ketones,two kinds of alkenes,two kinds of phenol and two kinds of furan.This study observed microbial compositions and enzyme activity in the fortified Daqu with Bacillus addition,and it further revealed the correlations between pivotal microbes and main flavor compounds.These results may help to develop effective strategies to regulate microbes for the brewing process and further improve the flavors of Jiang-flavor liquor.