| Guizhou is the place where Jiang-flavour Chinese spirits is the most abundant.With the "Moutai" and "Xi Jiu" series,Guizhou Jiang-flavour Chinese spirits always maintains the advantage of the pillar industries and becomes an economic industry with local characteristics.The brewing process of Jiang-flavour Chinese spirits is a complex and natural process of solid fermentation for multi bacteria.The environmental microbial community structure in brewing process of Jiang-flavour Chinese spirits is often the key factor to determine the yield and quality.To explore the microbial community structure characteristics and variation in Daqu and fermented grains for Jiang-flavour Chinese spirits brewing,it was helpful to understand the microorganism situation of Jiang-flavour Chinese spirits brewing environment,analyze the formation mechanism,provide guarantee measures for liquor production quality,and reduce pollutant emissions in the liquor making industry.It is of great significance to protect the ecological environment.At present,there is a lack of systematic research on the microorganisms in Daqu and fermented grains,while the study on the microbial community structure changes is relatively few.In this thesis,we used the High-Throughput Sequencing technology,based on Illumina Hiseq sequencing platform,to study the microorganism in two important processes of koji production and fermentation.The microbial community structure characteristics and variation were studied with Daqu and fermented grains.The following results were obtained with these methods such as OTU clustering,dilution curve,species abundance thermogram,microbiological annotation,LEfSe and correlation network analysis:(1)The species distribution of bacteria in Daqu and fermented grains was determined from different taxonomic levels.The dominant bacteria with relative abundance of more than 5% in Daqu are Firmicutes,Actinobacteria;Bacilli,Thallobacteria;Bacillales and Bacillaceae,Thermoactinomyceteae;Virgibacillus,Oceanobacillus,Kroppenstedtia,uncultured?bacterium?f?Bacillaceae and Bacillus.The dominant bacteria with relative abundance of more than 5% in fermented grains are Firmicutes;Bacilli;Lactobacillales,Bacillales;Lactobacillaceae,Bacillaceae,Thermoactinomycetaceae;Lactobacillus,uncultured?bacterium?f?Bacillaceae and Kroppenstedtia.(2)The distribution of fungal species in Daqu and fermented grains was determined from different taxonomic levels.The dominant fungi in Daqu and fermented grains are Ascomycota,Eurotiomycetes,Saccharomycetes;Sordariomycetes,Eurotiales,Saccharomycetals and Microascales;Aspergillaceae,Thermoascaceae,Trichocomaceae,Saccharomycopsidaceae and Pichiaceae;Aspergillus,Thermoascus,Monascus,Saccharomycosis and Thermomyces,et al.The species and relative abundance of fungi in Daqu and fermented grains were highly consistent.(3)Variation of bacterial and fungal communities from Daqu to fermented grains was explored.It was found that most bacterial species in fermented grains came from Daqu,while all fungal species could be found in Daqu.At each classification level,there were more bacterial and fungal species with similar relative abundance in Daqu samples than in fermented grains,which explained the uniformity of Daqu quality to a certain extent.From koji making to stacking fermentation,the colony structure characteristics of bacterial populations have changed significantly.Although Daqu and fermented grains have the same number of bacterial species,the same number and phase of bacteria,The large difference of abundance value between the two samples indicates that the reproduction rate and population structure of bacteria have changed greatly due to the change of environmental conditions.The smaller the classification level,the greater the change.However,the species and relative abundance of fungi in Daqu and fermented grains were highly consistent,and there was no significant difference in community characteristics.(4)The similarity and difference of bacterial and fungal community structure between Daqu and fermented grains was compared.At each classification level,Daqu has more bacterial and fungal species with similar relative abundance than fermented grains,which explains the uniformity of Daqu quality to a certain extent.Compare the difference of bacterial species relative abundance between fermented grains and Daqu at the phylum and genus classification level,the difference between upper and middle samples is small,while the difference between bottom samples is large.In terms of fungi,the relative abundance of fungal species in fermented grains was large,but the differences among species were also large;The relative abundance of fungal species in Daqu was slightly lower,but the differences among species were small.There were significant differences in bacterial species between Daqu and fermented grains.When the screening standard LDA score was > 4.0,there were 31 kinds of bacteria with greater differences than the screening standard,including 19 kinds in Daqu and 12 kinds in fermented grains;There are only 16 species of fungi,including 4 species in Daqu and 12 species in fermented grains.(5)Analysis of the interaction between bacteria and fungi in the production of Jiang-flavour Chinese spirits.Through the interaction network analysis of bacteria and fungi at the taxonomic level,the abundance of the species in Daqu and fermented grains has more related species and has strong interaction.In terms of bacteria,there are less abundant bacteria associated with fewer species but stronger interactions.There are also some bacterial genera with small abundance and no associated species.In terms of fungi,some species with low abundance basically do not have related genera.The above research results will provide a new way of thinking for exploring the causes and ways of environmental microorganism and related pollutants in the brewing process of Jiang-flavour Chinese spirits,and also provide technical clues and theoretical basis for improving the technological process,improving the yield and quality. |
PDF Full Text Request