Microbial Sources And Environmental Microbial Distribution Of The Sauce-flavor Baijiu In The Chishui River Producing Region

The sauce-flavor Baijiu is a fermented food that is produced openly through two stages of fermentation.Baijiu micro-ecologies include cellar micro-ecology,Daqu making microecology,fermentation environment,fermentation process and ecological environment,which involves hundreds of microorganisms.The fermentation process relies heavily on microorganisms in the environment.However,there has been no systematic research on the fermentation and ecological environment of sauce-flavor Baijiu.In this study,we selected 5distilleries and the ecological environment samples from the Chishui River producing area as the research objects,and used HS-SPME/GC-MS and Source Tracker to investigate the differences in flavor compounds and microorganisms of the fermented grains in MT and MX,and to investigate the effects of environment microorganisms on the fermented grains and to search for microbial distribution characteristics in the Chishui River producing area.The main findings of this study are as follows:(1)The differences in the microbial metabolism and community composition of fermented grains were investigated by HS-SPME/GC-MS,microbial environmental tolerance and inhibition experiments.At the end of fermentation,the concentration of acid in MX were higher(p=0.001),whereas the total ester content of MT(559.34 mg/kg)was higher than MX(434.00mg/kg).A.jinshanensis,A.pasteurianus and Pichia were the dominant microorganisms in MT,while in MX the dominant microorganisms were more diverse.Differences in the initial microorganisms led to microbial succession and metabolic changes during fermentation.The lack of dominant microorganisms and the low acidity of environment were the main reasons for the growth of other microorganisms.(2)High-throughput sequencing and Source Tracker were used to explore the contribution of environmental microorganisms to fermentation.Several brewing dominant microorganisms were found in the fermentation environment(such as pits,brewing sites,and tools),including Lactobacillus,A.jinshanensis,S.fibuligera,Pichia.Daqu(35.47%～61.42%)was the main source of bacteria in fermented grains.The fermentation environment(48.14%～58.71%)was the main source of fungi.Daqu mainly provided Bacillus and Thermoactinomyces,which provided the saccharifying enzyme for the fermentation.T.lanuginosus,S.fibuligera,Mucor and Pichia were present in the fermentation environments,ensuring that fermentation was completed.The initial microorganisms of fermented grains were influenced by microbial variations in the fermentation environment.The lactic acid bacteria in MX produced more fatty acid,while A.jinshanensis and Pichia in MT produced more total ester.(3)The correlation between microorganisms and environmental factors in Chishui River producing area was analyzed by high-throughput sequencing and correlation analysis.Pichia,Wickerhamomyces,Trichosporon,Debaryomyces,Penicillium,Aspergillus and Mucor were found in ecological environmental soils,which might be the microbial explanation for the Chishui River producing area’s appropriateness for brewing.The fungal Shannon index decreased with increasing altitude(r=-0.683,p=0.003),and Aspergillus,Rhodotorula,and Lichtheimia were found in low altitude soils.The distribution of fungi was greatly influenced by altitude,which explained why high altitudes are unsuitable for fermentation.We discovered the distance decay pattern of fermented-related microorganisms in the sauce-flavor Baijiu producing region.The fermentation process had less affected the ecological environment 50 m away from the distillery,demonstrating that the physical barrier,as well as some physical and chemical conditions,could reduce the risk of ecological environment pollution caused by Baijiu brewing.p H,acidity,and water content were the main environmental parameters that caused microbial changes in different environments.Extreme environments had screening effects on microbial colonization.Abiotic factors and microbial interactions synergistically led to microbial differences across environments.This study investigated for the flavor differences between the left and right banks of the Chishui River and the differences in microbial communities in the spirits and the environment.This study firstly clarified the characteristics of microbial distribution in the ecological environment,and systematically explored the relationship between the flavor of sauce-flavor Baijiu and environmental microecology,as well as the distribution and characteristics of microorganisms in the ecological environment,which is of great significance for improving the yield,quality and flavor of Baijiu.