Chinese strong-flavor liquor (CSFL) is in favour with the user because of its aroma and aftertaste long, which accounts for more than 70% of all Chinese liquor production. Microbes in pit mud play key roles in the fermentation cellar for the CSFL production. However, the previous studies on the pit-mud microbiota using traditional cultural and molecular methods cannot provide detailed phylogenetic compositions and cellar-age-related changes of the pit-mud microbial community.
In this study, prokaryotic community structure and diversity in pit-mud samples of Jiannanchun stock corpora of Sichuan with different cellar ages (1, 10, 25 and 50 years) were investigated using pyrosequencing technique. Results indicated that prokaryotic diversity increased with cellar age until 25-year old, and prokaryotic community structure changed significantly between three cellar ages (1, 10 and 25 years). Significant correlations between prokaryotic communities and environmental variables (pH, NH4+, lactic acid, butyric acid and caproic acid) were observed. Thus, this study suggested that long-term brewing operation shapes unique prokaryotic community structure and diversity, as well as pit-mud chemistry.
Moreover, a three-phase model to characterize the changes of pit-mud prokaryotic communities was proposed: Phase I is an initial domestication period. Pit mud is characterized by abundant Lactobacillus, high lactic acid and low pH; Phase II is a transition period. While Lactobacillus abundance decreases dramatically, Bacteroidetes and methanogens increase; Phase III is a relative mature period. Prokaryotic community owns highest diversity and capability to produce more caproic acid as a precursor for synthesis of ethyl caproate, the main flavor component in CSFL. This research provides scientific evidence to support “old fermentation cellars produce high quality liquor” .
More results have been published in Applied and Environmental Microbiology .The research got supports from the National Natural Science Foundation of China and 973 project of China.