Study On The Interaction Between Bacillus And Yeast In The Process Of Stacking Fermentation

High temperature accumulation is an important process of Maotai flavor Baijiu.Maotai flavor Baijiu production needs 9 times of accumulation,and the seasonal climate,temperature,humidity and raw material state of different rounds of accumulation vary greatly.Therefore,it is not enough to only use the stacking process.To understand the essence behind Baijiu brewing,it is necessary to further analyze the microbial composition and interaction in the fermented grains.And timely adjust the stacking time and stacking method to ensure the quality and output of Baijiu.Previous relevant studies have mostly focused on the composition and succession of microbial communities in fermented grains,but have not been able to reveal methods for controlling the stacking process and study microbial interactions.In order to explore the interaction between microorganisms in different environments during the stacking process,three functional strains were naturally selected from sauce flavored high-temperature Daqu and fermented grains,and their identification and characteristics were studied.Subsequently,simulated solid and liquid fermentation is conducted through a pure culture and co culture fermentation system,combining environmental factors and production processes during production.The specific research content and results are as follows:(1)Identification of main functional microorganisms;Using high-quality soy sauce flavored Daqu and fermented grains as the source of strains,soy sauce flavoring bacteria and yeast with strong fermentation performance were obtained through multiple rounds of screening.The bacteria XJ01 was identified as Bacillus licheniformis by 16s rDNA gene sequence analysis,the ester-producing yeast JM11 was identified as Ferbienser Lindner’s yeast by ITS gene sequence analysis,and the alcohol producing yeast JM12 was identified as Saccharomyces cerevisiae by ITS gene sequence analysis.Among them,Ferbienseb Lindner’s yeast is a non saccharomyces cerevisiae with relatively little research.This experiment will supplement the research on its physiological,biochemical and metabolic characteristics.(2)Research on microbial interaction under liquid conditions:Mixed culture of isolated microorganisms in sorghum liquid medium.Compared to pure cultured Bacillus,the addition of Saccharomyces cerevisiae and ester-producing yeast can significantly inhibit the growth of Bacillus,among which Saccharomyces cerevisiae has a strong inhibitory ability.Reducing the addition ratio of bacillus to yeast to 100:1 reduces the total acid,total ester,and alcohol content of the fermentation broth,but both types of yeast still exhibit strong inhibitory ability against bacillus.By increasing fermentation temperature and oxygen content,the inhibitory effect of Bacillus spp.is alleviated,while the growth of yeast is inhibited to some extent.Saccharomyces cerevisiae has a higher biomass than ester producing yeast,and has a strong temperature tolerance.Setting the initial fermentation pH,it was found that even in the experimental group with an initial pH of 8.0,the final pH still decreased to 4.35-4.41 after mixed fermentation,which could not alleviate the inhibitory effect on Bacillus.Adding a buffer to the fermentation broth can significantly counteract the inhibitory effect,indicating that one of the reasons for inhibiting Bacillus is the decrease in pH caused by yeast metabolic acid production.(3)Adding Interfacial Materials and Simulating Solid State Accumulation:Two types of interfacial materials,glass fiber and clay,were selected to enhance the solid-liquid interfacial effect.It was found that the addition of interfacial materials would increase biomass,reduce the total acid and alcohol content of the fermentation broth,and improve the ester-producing ability of ester-producing yeast,with the effect of clay being more obvious.It may be due to the lightweight structure of clay,which enhances the contact between microorganisms and air.After unifying the total amount of clay added and controlling the size of the clay particles added,it was found that as the particle size decreased(the number of particles increased),the clay particles more floated on the surface of the sorghum liquid and had a larger surface area.More oxygen entering and greater interfacial action enrich the nutrients in the raw material and increase biomass.Laboratory simulation of stacking found that further increasing the oxygen and interface of the stacking further alleviated its inhibitory effect,increased microbial biomass,and increased enzyme activity.After mixing,the metabolic flavor substances of different microorganisms complement each other,increasing the body richness of the wine.