Dynamic Evolution and Correlation between Metabolites and Microorganisms during Manufacturing Process and Storage of Fu Brick Tea

Abstract

Fu brick tea (FBT) is one of the major brands of dark tea. Microbial fermentation is considered the key step in the development of the special characteristics of FBT. The systemic corelationship of the microbiome and metabolomics during manufacture of Fu brick tea is not fully understood. In this study, we comprehensively explored the microbiome and metabolite dynamic evolution during the FBT manufacturing processes, and revealed decisive factors for the quality and safety of FBT based on the grouped methods of metabolomics combined with biochemical measurements, microbiome sequencing combined with quantitative polymerase chain reaction (PCR), and multiplex analysis. Both the microbiome and quantitative PCR showed that fungi displayed concentrated distribution characteristics in the primary dark tea samples, while bacterial richness increased during the flowering processes and ripening period. All microorganism species, as well as dominant fungi and bacteria, were identified in the distinct processes periods. A total of 178 metabolites were identified, and 34 of them were characterized as critical metabolites responsible for metabolic changes caused by the corresponding processes. Metabolic analysis showed that most metabolites were decreased during the FBT manufacturing processes, with the exception of gallic acid. Multivariate analysis verified that the critical metabolites were correlated with specific dominant microbial species. All the top fungal species except unclassified_g_ Aspergillus showed positive correlations with six critical metabolites (L-The, epigallocatechin (EGC), Gln, tea polyphenol (TP), tea polysaccharides (TPs) and caffeine). Five of the top bacteria species (Cronobacter, Klebsiella, Pantoea, Pluralibacter, and unclassified_ f_Entero-bacteriaceae) showed positive correlations with epigallocatechins and tea polyphenols, while the other 11 top bacterial species correlated negatively with all the critical metabolites. The content of amino acids, tea polyphenols, tea polysaccharides, and flavonoids was reduced during microbial fermentation. In conclusion, our results reveal that microbial composition is the critical factor in changing the metabolic profile of FBT. This discovery provides a theoretical basis for improving the quality of FBT and enhancing its safety.

Identification of characteristic aroma and bacteria related to aroma evolution during long-term storage of compressed white tea

“…These enzymes can be involved in the synthesis or degradation of tea aroma (39). Previous studies have shown that bacteria can secrete extracellular enzymes during tea storage, thereby affecting the quality of tea (17). This study also verified this conclusion through the prediction of bacterial function.…”

“…Previous studies have found that microorganisms play an important role in the transformation of tea aroma during storage, among which bacteria may play a key role (17). Combined with the previous bacterial community data of CWT in different storage years (Supplementary Table 4) (20), PICRUSt2 was used to predict and analyze the function of bacteria, and acquire the information that bacteria in CWT storage process could participate in 264 KEGG metabolic pathways.…”

“…However, there are few reports on the relationship between aroma characteristics and VOCs during storage of CWT. In addition, microorganisms may play a key role in the changes of tea metabolites during storage (3), which has been confirmed in Fu Brick tea, Liupao tea, and Pu-erh tea (16-18), and it is found that the diversity of bacteria increases gradually during the storage process of tea, mainly involved in the decomposition, transformation and degradation of small molecule compounds (17). Previous study have identified bacterial communities during storage of white tea and CWT, and performed functional prediction.…”

Fu brick tea protects against high-fat diet-induced obesity phenotypes via promoting adipose browning and thermogenesis in association with gut microbiota

“…Fu brick tea is generally consumed as a decoction from boiling water. Benefiting from the well-studied microbial succession and dynamic changes in chemical components during the manufacturing process and storage, [4][5][6] it is indisputable that Fu brick tea soup is composed of various water-soluble bioactive substances, including polyphenols, polysaccharides, theabrownin and soluble dietary fiber. Recently, theabrownin and polyphenols from Fu brick tea have been shown to reduce obesity and the associated metabolic disorders of mice fed with a high-fat diet via modulating the intestinal microbiome.…”

Modulation effects of microorganisms on tea in fermentation

“…As shown in Figure 2 , there are four important structures of catechins, namely (-)-epigallocatechin-3-gallate (EGCG), (-)-epicatechin-3-gallate (ECG), (-)-Epicallocatechin (EGC) and (-)-Epicatechin (EC). In the process of tea fermentation, the content of catechin varies with the degree of tea fermentation, fermentation time, fermentation temperature and other factors ( 30 ). In another study, Qin et al using the method of quantitative analysis and high performance liquid chromatography to study the change of tea polyphenols content of pu-erh tea in solid-state fermentation system, it was found that the content of ester-catechins increased slightly at the initial stage of fermentation, and then the ester-catechins gradually degraded to produce catechin and gallic acid.…”