Metabolomic Investigation Of Microbial Fermentation Process Of Jing-wei Fu Brick Tea

Fu brick tea belongs to post-fermented tea products,and it is one of the dark tea,which is processed with the most unique and complicated processing technology.Fu brick tea is predominated generally with golden yellow spots,called “golden flora”,which is the key characteristics discriminated with the other kinds of brick tea.The microbial fermentation process was reported to allow for a large growth of Eurotium spp.And this is the main cause of “golden flora”.Additionally,the amount of “golden flora” is officially identified as the most important marker for the quality of Fu brick tea,because “golden flora”contributes to the unique flavor and function.Therefore,the microbial fermentation process is identified as the most important phase for the processing of Fu brick tea.Although there have been some investigations on the biochemical profile of Fu brick tea,the exact biochemical variation remained to be further explored.Moreover,lots of these investigations focused on the phytochemicals,including extraction and purification of some compounds or one group of substances.So far,the systematic biochemical compositional variation of Fu brick tea remained to be further explored.In this study,we applied LC-MS based metabolomics to investigate the microbial fermentation process of Fu brick tea.The main context of this research included:1.Three kinds of Fu brick tea samples(FBT Ori,FBT BF and FBT)and other ten kinds of tea samples(full-fermented tea samples,partially-fermented tea samples and non-fermented tea samples)were subjected to principal component analysis(PCA),which visually displayed the discrimination of different kinds of tea samples and the biochemical variation during the processing of Fu brick tea.And this determined the importance of microbial fermentation process on the biochemical profile of Fu brick tea.Then the loading plots further identify these significant altered compounds,which contributed mostly to the discrimination of different kinds of tea samples.Our results were compared with other research,which verified the application of LC-MS based metabolomics on the tea research.2.Four different tea samples from the microbial fermentation process were investigated,including tea samples taken before the microbial fermentation process(FBT BF),tea samples taken at sixth day(FBT sixth)and ninth day(FBT ninth)during the microbial fermentation,the final tea product samples after the microbial fermentation process(FBT).Metabolomics including partial least Square discrimination analysis(PLS-DA)and hierarchical cluster analysis(HCA)were applied to explore these significantly altered compounds during the microbial fermentation process.31 compounds were identified as the significantly altered compounds,17 compounds decreased and other14 increased.Our results verified the special metabolic pathway involved in B ring fission catechins and L-theanine,moreover,these pathway have not been reported in other kinds of tea,which determined that the unique influence of these bacterial on the metabolic profile of Fu brick tea.