Analysis Of Microbial Community And Diversity In Pit Mud Of Zhijiang Liquor

Zhijiang liquor is a type of Luzhou-flavor liquor, fermented in a pit that contains rich microbial communities in its mud. The microbes dictate the quality of liquor by producing functional enzymes, alcohol, acids and esters. These metabolites contribute to the precursors that give the liquor a distinct aroma.Therefore, investigating the microbial community and diversity in the pit mud at three cellar ages provides the scientific evidence for the production and quality improvement of Luzhou-flavor Zhijiang liquor.In the current research, we sampled pit mud at three cellar ages and determined the distribution of bacteria and fungi in these samples using PCR-DGGE and high-throughput sequencing. We then isolated culturable bacteria from these samples by traditional culture methods in order to identify the functional bacteria and fungi that constitute pit mud.Analysis of the PCR-DGGE and high-throughput sequencing results reveal that the bacteria in the pit mud of Zhijiang liquor comprised 3 phyla: Firmicutes,Synergistetes and Bacteroidetes; The relative abundance of Clostridium and Caloramator, which were the predominant genera(≥ 1.0%) in both samples, were fuond to increase gradually as the cellar age raised; In contrast, the relative abundance of Syntrophaceticus, Syntrophomonas, Sedimentibacter and Lactobacillus were found to decrease with increasing cellar age; Aminobacterium was found to predominate only in the 20- and 30-year pit mud samples; The predominant fungal groups in pit mud of Zhijiang liquor were Ascomycota, Basidiomycota and Zygomycota; with Candida sp., Saccharomycopsis fibuligera, Thermoascus crustaceus and Eurotium sp.being the most abundant fungi(≥ 1.0%) in both samples; The relative abundance of Rhizopus sp., Eurotium sp., Wickerhamomyces anomalus and Thermoascus sp.increased gradually with increasing cellar age; while Trichosporon sp. and Eurotium athecium were found to predominante only in 10-year pit mud sample; Pit mud at 20 years had the most diverse bacterial community while pit mud at 30 years had thehighest fungal community diversity.There were some bacteria isolated from pit mud by traditional culture method,including 11 strains of aerobic bacteria: Thermoactinomycetaceae, Staphylococcus sp.,Bacillus firmus, Bacillus circulans and so on; 6 strains of facultative anaerobic bacteria:Bacillus sporothermodurans, Bacillus circulans, Bacillus vallismortis and others; 5strains of anaerobic bacteria: Clostridium tyrobutyricum, Clostridium sp., Clostridium aminovalericum, Eubacterium contortum and Clostridium butyricum.