Screening Of Excellent Brewing Microorganisms In Ilite Daqu (Strong Flavor Type) And Its Application In Chuanfa Xiaoqu Liquor

Distiller’s yeast is the main source of microorganisms in the brewing fermentation system,and its microbial community structure and quantity ratio are important factors affecting the style characteristics of liquor.In order to explore the application effect of brewing microorganisms in strong flavor Daqu in Chuanfa Xiaoqu liquor,this study selected Ilite strong flavor Daqu as the research object and used different methods to screen brewing microorganisms.Finally,yeast strains with high ethanol production and molds with high saccharification and liquefaction enzymes were screened out;Using the screened yeast and mold to prepare pure Fuqu,the solid-state fermentation conditions were optimized,the fermentation cycle was determined,and the physicochemical indicators of the fermented grains during the fermentation process,as well as the content of ethanol,total esters,and total acids in the fermented grains after fermentation,were measured to preliminarily explore the application effect of brewing microorganisms.The main research content and results are as follows:(1)Using strong flavor Daqu as the screening material,a yeast strain LX-2 with high ethanol production capacity and fermentation performance was screened.After 26 S rDNA molecular identification,it was preliminarily identified as Saccharomycosis fabuligera.After 7 days of fermentation,the ethanol,total ester,and total acid contents of the fermentation broth of this yeast reached 5.40%,0.174 g/L,and 0.068 g/L,respectively;Based on the transparent ring method and enzyme activity re screening,a mold JW-3 with high production of saccharifying and liquefying enzymes was screened.Through microscopic observation and18 S rDNA molecular identification,it was preliminarily identified as Lichtheimia corymbifera.The saccharifying and liquefying enzyme activities of this strain in the enzyme activity re screening medium reached 409.67 U/g and 1391.5 U/g,respectively.(2)Optimize the Fuqu making conditions for yeast Fuqu and fungal Fuqu through single factor experiments and response surface methodology experiments.The results showed that the optimal cultivation conditions for yeast Fuqu were 11% inoculation amount,29 ℃ cultivation temperature,54 h cultivation time,and 55% water content.Under these cultivation conditions,the average ethanol content of the fermentation broth was 6.17%;In addition,the optimal cultivation conditions for fungal Fuqu are 10% inoculation amount,30 ℃ cultivation temperature,91 h cultivation time,and 55% water content.Under these cultivation conditions,the activity of fungal Fuqu saccharifying enzyme is 409.67 U/g,and the activity of liquefaction enzyme is 1597.00 U/g.(3)Simulated solid-state fermentation experiments were conducted using yeast and mold purebred Fuqu.Through single factor experiments and response surface methodology,the optimal conditions for solid-state fermentation were determined to be a mixture ratio of 2.5:1,a fermentation temperature of 28.5 ℃,and an inoculation amount of 9%.Under these conditions,the solid-state fermentation system had a fermentation capacity of 6.89 U and a fermentation cycle of 11 d.The analysis of the physicochemical indicators of the fermented grains during the fermentation process showed that the temperature of the fermented grains was higher than the ambient temperature 3 days before fermentation,and the highest temperature reached 30 ℃on the 2nd day of fermentation;The moisture content of the fermented grains continued to increase during the fermentation process,and at the end of fermentation,the moisture content of the fermented grains increased by 10.04% compared to the beginning of fermentation;The acidity and starch content of the fermented grains continued to decrease with the extension of fermentation time.At the end of fermentation,the acidity and starch content of the fermented grains decreased by 76.67% and 33.90%,respectively,compared to the initial stage of fermentation;The reducing sugar content of the fermented grains showed a trend of first increasing and then decreasing during the fermentation period.The content reached its highest value of 1.44% on the third day of fermentation,and decreased to 1.15% at the end of fermentation;By comparing the differences in ethanol,total ester,and total acid content between pure strain Fuqu fermented J and finished product Fuqu fermented J at the end of fermentation,it was found that compared to finished product Fuqu fermented J,the ethanol content of pure strain Fuqu fermented J was 26.92% lower,while the total ester and total acid content were 190.68% and 40.74% higher,respectively.