Study On The Effect Of ’ Jinhua Fungus’ Fermentation On The Composition And Taste Of Pu-Erh Tea And Its Mechanism

Eurotium cristatum,commonly known as ’ Jinhua’,is a fungus of Eurotium,which belongs to the genus Eurotium.It can be used to ferment tea,reduce the astringency of tea,and enhance the quality of tea.The metabolites of the bacteria have various effects such as lipid-lowering,anti-tumor cell activity,and digestion promotion.The mycelium is rich in nutrients and is not toxic to the human body,so it is of great research value.Yunnan Province is the center of the origin of tea trees.Tea planting and utilization have a long history,and ancient tea tree resources are abundant.Ecological advantages,cultural advantages,resource advantages and germplasm advantages have created the unique quality of Yunnan tea.Tea has become an important plateau economic crop and the most potential green food industry in Yunnan Province.According to statistics,more than 100 counties(cities,districts)in 15 states(cities)of the province produce tea.The planting area of tea trees is leading in the country,and tea farmers have reached more than 6 million.Nevertheless,the low-end Pu ’er in Yunnan Province does not have a good market.Therefore,in this study,Lincang Pu ’er raw tea,Yunnan black tea and other tea were used as the main experimental materials to purify and isolate Eurotium cristatum,and the optimal temperature and water content of the selected dominant strains were determined.At the same time,it was found that light had a significant effect on the growth of Eurotium cristatum.On this basis,the changes of biochemical components and sensory evaluation of tea fermented by Eurotium cristatum were studied.Finally,the mycelia cultured in the water extract of Lincang Pu ’er raw tea and Lincang Pu ’er ripe tea were subjected to transcriptome determination and analysis with the mycelia cultured in potato as a control,hoping to analyze the effect of Eurotium cristatum on the changes of biochemical components in the fermentation of Yunnan large-leaf tea.It provides scientific support for further exploring the resources of golden flower strains,the industrialization and scale development of Yunnan ’ Jinhua ’ Pu ’er tea and the construction of brand.’CR-VS-CF ’(Eurotium cristatum in Pu ’er raw tea VS Eurotium cristatum in Pu ’er ripe tea)screened 2822 differentially expressed genes,of which 1682 were up-regulated and 1140 were down-regulated.The main results are as follows :1.The isolation and purification of Eurotium cristatum were carried out by using the medium of different tea extracts,found that the production of various types of tea extract liquid medium,there are obvious ’ Jinhua ’ single colony growth,and colony growth is relatively good,transferred to the PDA medium single point culture,no obvious pollution,after morphological identification and ITS sequencing,the selected strain was the target strain of ’ Jinhua fungus ’.The efficient separation and purification of Eurotium cristatum can be achieved by using tea extraction liquid medium,which can greatly shorten the experimental time,speed up the experimental progress and improve the experimental efficiency.2.The colonies with good growth were sent to the company for sequencing and homology analysis,and the sequences with relatively high homology were analyzed by bioanalysis software Mega 5.0,and the sequence phylogenetic tree was constructed.Two strains of Aspergillus cristatum,seven strains of Aspergillus pseudoglaucus,two strains of Eurotium isolates,two strains of Aspergillus brown,one strain of Aspergillus shevard,one strain of Aspergillus amsterdam,and one strain of Eurotium cristatum were obtained.3.The culture conditions of the selected Eurotium cristatum were screened,and different temperatures,water content and light were set for culture.Gradient experiments were carried out to screen out suitable culture conditions.The results showed that the optimum temperature of Eurotium cristatum was 25°C-30°C,and the optimum water content was 45%-48%.Continuous illumination can greatly increase the growth rate of Eurotium cristatum.4.In order to screen out what Yunnan tea is most suitable for inoculation of Eurotium cristatum.Lincang large-leaf Pu ’er raw tea,Yunnan black tea and Yunnan green tea were fermented by artificial inoculation of Eurotium cristatum.The results showed that Eurotium cristatum was most suitable for inoculation of Lincang large-leaf Pu ’er raw tea,followed by Yunnan black tea,and finally not suitable for inoculation of Yunnan green tea.Through principal component analysis and least squares function in linear regression,it is verified that the quality of Lincang large leaf Pu ’er raw tea has been greatly improved.5.Transcriptome determination and analysis were performed on four materials :Eurotium cristatum cultured in Pu ’er raw tea,Eurotium cristatum cultured in Pu ’er ripe tea,Eurotium cristatum in Pu ’er raw tea cultured in potato medium and Eurotium cristatum in Pu ’er ripe tea cultured in potato medium.It was found that ’ CR-VS-R ’(Eurotium cristatum in Pu ’er raw tea VS Eurotium cristatum in Pu ’er raw tea cultured in potato medium)had 3903 differential genes,of which 1607 were up-regulated and 2296 were down-regulated.’R-VS-F ’(Eurotium cristatum in Pu ’er raw tea cultured in potato medium VS Eurotium cristatum in Pu ’er ripe tea cultured in potato medium)screened 4422 differentially expressed genes,of which 2577 were up-regulated and 1845 were down-regulated.’CF-VS-F ’(Eurotium cristatum in Pu ’er ripe tea VS Eurotium cristatum in Pu ’er ripe tea cultured in potato medium)screened3286 differentially expressed genes,of which 1355 were up-regulated and 1931 were down-regulated.GO functional analysis showed that differentially expressed genes were mainly enriched in metabolic processes,cell processes,and single biological processes.Molecular functions were mainly enriched in catalytic activity and binding.Cell components were mainly enriched in cells,cell components,and organelles.KO analysis showed that differentially expressed genes were mainly enriched in a large number of genes enriched to the global and overview pathways,carbohydrate metabolism,amino acid metabolism,lipid metabolism,translation,folding classification degradation pathway,replication and repair,transport and catalysis,cell growth and death,signal transduction and membrane transport pathways.The synthetic genes involved in the synthesis of catechin and theanine were found,and the expression levels of these genes were analyzed.The results showed that the change of chemical composition and taste of large leaf tea fermented by Eurotium cristatum was the result of material transformation promoted by related gene expression products.