Study On The Microbial Community And Metabolites Of Fermented Grains In The New Fermentation Model Of Luzhou-flavor Wine

Traditional Luzhou-flavor liquor is a typical fermented product of natural mixed microorganism,muddy,and workshop-style production.There are two remarkable features:One is to use the brewing microorganisms of mud to participate in fermentation process in the mud pit;the other is that the temperature of fermentation changes with production season and fermentation process,and the production mode is not conducive to effective intervention in the fermentation process,so that the product quality fluctuations with the production season and also restrict the process of mechanization and standardized production in the industry.The new fermentation mode of Luzhou-flavor liquor is based on the traditional fermentation process,using solid fermenter replace pit-mud,high-quality yellow water replace mud,artificially interfering with the fermentation temperature,and fermentation out of pit-mud without mud.Solid-state temperature-controlled fermentation technology,which can be the key basis for the production of Luzhou-flavor liquor from the traditional way to mechanized and standardized production,and producing high-quality Luzhou-flavor liquor in different places.In Luzhou Laojiao Company,our group conducted relevant tests using 2.4 m~3steel fermenters in early stage,and achieved good results.However,the test can not rule out the influence of the traditional brewing environment microorganisms,and the temperature uniformity of the dregs in the fermenter was poor,The temperature difference between the two fermenters is not obvious,there are problems such as the lack of clarity on the influence of temperature on the test results,especially the changes in the microbial community during the fermentation process.Based on the above research,this paper breaks away from the traditional production environment,replaces the mud with yellow water,after the natural temperature rise in the initial stage of fermentation,and designs three fermentation temperatures of high temperature H(36°C),medium temperature M(30°C),low temperature L(24°C),and study on the microbial community and metabolites of the new fermentation mode of Luzhou-flavor liquor in the laboratory.The main results are as follows:1.The new fermentation mode has no adverse effect on the physical chemical properties and the formation of the main flavor substances of the fermented grains.The changes in physical and chemical indicators of the dregs are similar to those of the traditional fermentation and the previous test group.Out of the traditional brewing environment,a total of 105 volatile components were identified.The higher temperature is more favorable for the formation of?-phenylethanol.The medium temperature fermentation has a promoting effect on the formation of ethyl lactate,while inhibiting the formation of ethyl hexanoate.The lower temperature fermentation is beneficial to increase the content of ethyl hexanoate and lower the content of ethyl lactate and promote the formation of ethyl acetate and ethyl butyrate,and also beneficial to reduce the formation of furfural.2.The new fermentation mode has no obvious effect on the variation of aerobic microorganisms in the dregs.Similar to the traditional fermentation mode,the number of yeasts and molds decreases rapidly in high temperature fermentation,medium and low temperature fermentation has more aerobic bacteria and yeast than high temperature fermentation.3.Under the new fermentation mode,the temperature has different effects on the microbial community structure of bacteria,fungi and archaea in the dregs.Reflected in:(1)Lactobacillus,Thermoactinomyces,Acetobacter,Bacillus and Caproiciprodu cens were the main bacterial species in the fermentation process,the main bacterial genus is the same at different fermentation temperatures,similar to existing studies.Higher temperature fermentation can promote Lactobacillus to become a dominant genus faster,enriching Thermoactinomyces and Prevotella,and enriching Caproiciproducens to produce hexanoic acid.Lower temperature fermentation is beneficial to the Lactobacillus genus to maintain its superiority and metabolize lactic acid production.(2)In fermentation process,we identified 18 families and 121 fungal genus.The main fungi belonged to Aspergillus,Candida,Thermomyces,Trichosporon,Thermoascus,Zygosaccharomyces.Candida is the main advantage genus of the fermentation process.The lower temperature favors Candida,Trichosporon,and Zygosaccharomyces to maintain activity,which is conducive to continuous wine production,while higher temperature fermentation contributes to the advantage of Aspergillus.(3)The diversity of the archaea was dynamically changed,and 21 archaea were identified from the dregs.The genus Methanobacterium,Methanosarcina and Methanobrevibacter are dominant archaea,which are consistent with the archaea in mud.The higher abundance of Methanobacterium at higher temperatures,and the lower temperature is beneficial for Methanobrevibacter to remain active in the late fermentation stage,contributing to the production of hexanoic acid.Methanosarcina may participate in the formation of ethyl butyrate.In summary,we believe that the new fermentation mode of Luzhou-flavor liquor--solid-state temperature-controlled tank-type mud-free fermentation technology is feasible.The study also found that the fermentation temperature has an important influence on the proportion of dominant microbial species and the formation of flavor substances in the dregs.This study provide a methodological basis and theoretical basis for regulating the microbial community structure through temperature control,optimizing the quality of Luzhou-flavor liquor and the standardized production of Luzhou-flavor liquor.