Effects Of EGCG In Fuzhuan Tea On Aspergillus Cristatus

Hunan Anhua Fuzhuan tea is a kind of dark tea,and it is also a popular functional drink on the market.Eurotium cristatum is the dominant strain in the fermentation process of Fuzhuan tea,and it forms golden plaques in tea bricks,which are called golden flowers.The number of golden flowers determines the quality of Fu brick tea.After being fermented by Eurotium cristatum,the taste,flavor and unique functional quality of Fuzhuan tea have been significantly improved.EGCG(epigallocatechin gallate)is a functional component of Fuzhuan tea.It is an ester-type catechin monomer of tea polyphenols.It has significant biological activities such as anti-oxidation,anti-inflammatory and anti-cancer.Studies have shown that the content of EGCG in Fuzhuan tea is significantly reduced after fermentation by Eurotium cristatum.The previous research of our group found that the growth of Eurotium cristatum in the medium containing Fuzhuan tea was better than that without Fuzhuan tea.Therefore,Eurotium cristatum is likely to be one of the main factors causing the decrease of EGCG content,and EGCG or its transformation product promotes the growth of Eurotium cristatum.If the correlation between the two can be clarified,it can provide basis and guidance for the development of Fuzhuan tea and further quality research.However,there are no relevant studies and reports so far.In this study,fungal molecular biology identification,HPLC,LCQTOF MS,transcriptomics and other methods were used to purify and identify the dominant Eurotium cristatum in Anhua Fuzhuan tea;the transformation effect of this strain on EGCG was clarified;The effect of EGCG on the bacteria was analyzed from the gene level.The main research conclusions obtained are as follows:1、The dominant strains on Fuzhuan tea were isolated and purified and identified.The “golden flowers” were picked from the commercially available Fuzhuan tea,separated,purified and cultured in the medium.Morphologically,it was initially identified as Eurotium cristatum.Molecular biological identification was carried out using 18 S r RNA sequence,and the purified strain was finally determined to be Aspergilus cristatus(GTQM).2、To verify the transformation effect of GTQM strain on EGCG.The fermentation supernatant and strain liquid of GTQM strain were obtained by liquid nitrogen crushing and centrifugation,and the enzymes were immobilized by immobilization method,and then reacted with EGCG for 48 h respectively.Changes in the content of EGCG before and after the reaction were detected.The results showed that after the reaction for 48 h,the EGCG content in the immobilized fermentation supernatant decreased by 56.57%,and the EGCG in the immobilized broken liquid decreased by 77.17%,and the decrease rates were 11.6% and 32.2%higher than those of the control,respectively.The EGCG conversion products were analyzed by LC-QTOF MS,and it was found that EGC(epigallocatechin)and GA(gallic acid)were mainly produced.3、Transcriptomic analysis of the effect of EGCG on GTQM strains.GTQM strains were treated with EGCG for 72 h,and the untreated group was used as a control to detect the gene expression of GTQM strains by RNA-seq technology.The results showed that there were 85 up-regulated genes and 79 down-regulated genes in the strains.Using GO,KEGG,KOG and other databases to conduct gene enrichment analysis on differentially expressed genes,it was found that these genes are mainly concentrated in pathways such as transport,signal transduction,glycolysis,and ribosome production,at the same time,multiple hydrolases and oxidoreductases are included in the highly expressed genes.The results indicate that GTQM bacteria may transform EGCG through hydrolysis,redox,etc.,and take the transformed product into the cell for utilization.