Diversity And Dynamics Of Yeasts And Bacteria During The Solid State Fermentative Process Contributing To Chinese Maotai-flavor Liquor Making

Maotai-flavour liquor is one of the most famous Chinese liquors. Due to its uniquefermentation process, the microbial diversity in fermented grains was complex, then led to theunique flavor style. Therefore, it would be useful to investigate this microbial diversitysystematically, which would help us further understand the fermentative mechanism ofMaotai-flavor liquor and improve its quality.In this study, we used two kinds of selective media, combined with molecularidentification method, to systematically analyze the diversity of yeasts and bacteria in thewhole fermentative process of Maotai-flavor liquor making. And then we analyzed theircontribution on the formation of Maotai-flavor with statistical analysis software. In addition,the function of a dominant bacterium, Bacillus amyloliquefaciens, was studied.The major conclusions are as follows:(1) Sixteen yeast species and21bacterial species were identified during the solid statefermentative process contributing to Chinese Maotai-flavor liquor making, from environment,high-temperature Daqu and fermented grains by using Wallerstein laboratory nutrient (WLN)agar medium and improved nutrient broth agar medium. Among them,7yeast species and10bacterial species was reported for the first time in Maotai-flavor liquor. The yeasts in grainsduring stacking fermentation were mainly from the ground, but bacteria were mainly fromhigh-temperature Daqu.(2) Zygosaccharomyces bailii, Saccharomyces cerevisiae, Bacillus licheniformis and B.amyloliquefaciens were predominant species in grains during alcoholic fermentation in pits.The population of yeast was452-fold difference at the beginning of different stackingfermentation rounds, but less than10times difference in the end, which means stackingfermentation could regulate the population of yeast to reduce difference between differentrounds. The multiplication of bacteria was between1.3to5.5times. Temperature and oxygenwere the main factors influencing microorganisms’ multiplication during stackingfermentation.(3) The species of yeast and bacteria were basically the same in top, middle, and bottomlayer during alcoholic fermentation in pits. Z. bailii, Schizosaccharomyces pombe, S.cerevisiae, B. licheniformis and B. amyloliquefaciens were the main species. Principalcomponent analysis showed that Z. bailii, S. cerevisiae, S. pombe, B. licheniformis, B.amyloliquefaciens and Bacillus subtilis were the principal components to distinguish the toplayer from the other layers, which implied they could be the key microorganisms in formingMaotai-flavor.(4) This study found that the dominant bacteria in Maotai-flavor liquor making process,B. amyloliquefaciens, had better ethanol tolerance than the type culture strain, which is up to16%. And the low ethanol concentrations,2%and4%, could promote its growth and improvethe content of organic acids and ester compounds significantly.