Study On Microbial Diversity Of Sichuan Dark Tea During Post-fermentation And Airborne Microbial In Fermentation Workshop

There was a large number of microbial reproduction and growth in Sichuan dark tea during post-fermentation.These microbes were very important for the formation of quality of Sichuan dark tea.At present,the study of dark tea microbes in Sichuan is mainly focused on the separation and identification,and it's rare of the research on the microbial diversity of Sichuan dark tea.In recent years,Denaturing gradient gel electrophoresis(PCR-DGGE)has been widely used in microbial community structure and diversity studies,because of the fact that 85%to 99%of microbes were still not cultivated in nature.This technology can avoid the culture of microorganism,and has a lot of superioritis,such as a good repeatability,high reliability,easy operation,etc.In this study,the microbial diversity of Sichuan dark tea was studied by PCR-DGGE technique,and the microbes of different growth phases were identified and the dynamic characteristics of microbial community in the whole process were explored.In addition,this study used traditional culture and the molecular identification method to study the airborne microbial in fermentation workshop of Sichuan dark tea,in order to provide some bases for the study of the source of microbes in Sichuan dark tea.The pile fermentation is the key procedure to form the quality of Sichuan dark tea,and it is of great significance to improve the quality and perfect the production process of Sichuan dark tea by studying the changes of the main quality components in the pile fermentation process of Sichuan dark tea.The major results are as follows:(1)The microbial diversity of Sichuan dark tea was studied by PCR-DGGE.The results show that:the diversity index of bacteria was the highest in start fermentation stage and first fermentation stage(H'=2.398),and the diversity index was highest in end fermentation stage(H'=2.197).The composition of the bacterial community changed significantly in second fermentation stage(the similarity of the community structure was only 12%between second fermentation stage with others),and the composition of the fungal community at the end fermentation stage was drastically changed(the community Similarity was only 12%between end fermentation stage with start fermentation stage).The results of identification of dominant microorganisms during the whole pile fermentation process of Sichuan dark tea show that,2 groups of bacteria,including y-proteobacteria and Bacilli presented during the Sichuan dark tea fermentation.The dominant species during the pile fermentation were the bacterium sp.2 groups of fungi,including Eurotiales and Saccharomycetales presented.Eurotiales were the main dominant flora during the pile fermentation,and the dominant species were Aspergillus.In addition,8 genera of bacteria and 8 genera of fungi were identified from the tea samples of different periods,including eubacterium,bacterium,Staphylococcus gallinarum,Pseudomonas putida,Burkholderia cepacia,Microbacterium sp.,Serratia marcescens,Marinococcus sp.,Debaryomyces hansenii,Thermomyces lanuginosus,Geosmithia argillacea,Penicillium commune,Eurotium athecium,Aspergillus niger,Aspergillus tubingensis,Aspergillus fumigates.There were differences in the dominant bacteria in different pile fermentation periods.Among them,the dominant bacteria are the bactrium sp.in start fermentation stage,first fermentation stage and end fermentation stage,while the dominant bacteria are Burkholderia in second fermentation stage.The dominant fungi were Geosmithia argillacea in start fermentation stage and second fermentation stage,while the dominant fungi are the Debaryomyces hansenii and Aspergillus fumigates in first fermentation stage and end fermentation stage.(2)Through the natural sedimentation method,the airborne microbial of fermentation workshop of Sichuan dark tea were collected.The airborne microbial were identified by the combination of morphology and molecular biology,which were 6 common molds,5 kinds of bacteria and 4 kinds of actinomycetes,including Mucor racemosus,Aspergillus niger,Mucor sp.,Penicillium crustosum,Penicillium citrinum,Aspergillus fumigatus,Bacillus thuringiensis,Staphylococcus sp.,Bacillus sp.,Bacillus subtilis,Brevundimonas sp.,Streptomyces cellulosae,Streptomyces lavendulae,Streptomyces praecox,Streptomyces thermocarboxydus.Among them,Aspergillus niger,Aspergillus fumigatus and Bacillus sp.were found in Sichuan dark tea pile.(3)Study of the changes in the content of biochemical components of Sichuan dark tea pile fermentation showed that tea polyphenols,catechins,theaflavins,thearubigins,water soluble sugar and water soluble pectin were decreased trend in the pile fermentation process.The content of theabrownin was increased at the first and then decreased,the end fermentation stage increased slightly.the amino acid content decreased first and then increased,the overall downward trend.The caffeine content reduced after the first increase in pile fermentation process,caffeine content no significant change until the end fermentation stage.The temperature of the tea stock was maintained at 49.2?-63.5?.On the 16th day,the temperature of the tea billet was the highest,reaching 63.5?.The water content of the tea billet increased first and then decreased.On the 8th day,the water content of the tea was the highest,There was no significant change in the water content of the tea stock.The pH value of the tea stock gradually decreased from the beginning of the pile and was weakly acidic.