Rolling forms the diversities of small molecular nonvolatile metabolite profile and consequently shapes the bacterial community structure for Keemun black tea.

The detailed dynamics of small molecular nonvolatile chemical and bacterial diversities, as well as their relationship are still unclear in the manufacturing process of Keemun black tea (KMBT). Herein, mass spectrometry-based untargeted metabolomics, Feature-based Molecular Networking (FBMN) and bacterial DNA amplicon sequencing were used to investigate the dense temporal samples of the manufacturing process. For the first time, we reveal that the pyrogallol-type catechins are oxidized asynchronously before catechol-type catechins during the black tea processing. Rolling is the key procedure for forming the small molecular nonvolatile metabolite profile (SMNMetProf), increasing the metabolite richness, and then shaping the bacterial community structure in the KMBT manufacturing process, which decreases both molecular weight and molecular polarity of the small molecular nonvolatile metabolites. The SMNMetProf of black tea is formed by the endogenous enzymatic oxidation of tea leaves, rather than bacterial fermentation.

Dynamic Changes in the Microbial Community and Metabolite Profile during the Pile Fermentation Process of Fuzhuan Brick Tea.

The pile fermentation process of Fuzhuan brick tea is unique in that it involves preheating without the use of starter cultures. The detailed metabolite changes and their drivers during this procedure are not known. Characterizing these unknown changes that occur in the metabolites and microbes during pile fermentation of Fuzhuan brick tea is important for industrial modernization of this traditional fermented food. Using microbial DNA amplicon sequencing, mass spectrometry-based untargeted metabolomics, and feature-based molecular networking, we herein reveal that significant changes in the microbial community occur before changes in the metabolite profile. These changes were characterized by a decrease in Klebsiella and Aspergillus, alongside an increase in Bacillus and Eurotium. The decrease in lysophosphatidylcholines, unsaturated fatty acids, and some astringent flavan-3-ols and bitter amino acids, as well as the increase in some less astringent flavan-3-ols and sweet or umami amino acids, contributed importantly to the overall changes observed in the metabolite profile. The majority of these changes was caused by bacterial metabolism and the corresponding heat generated by it.

Microbial and Nonvolatile Chemical Diversities of Chinese Dark Teas Are Differed by Latitude and Pile Fermentation.

Understanding the microbial and chemical diversities, as well as what affects these diversities, is important for modern manufacturing of traditional fermented foods. In this work, Chinese dark teas (CDTs) that are traditional microbial fermented beverages with relatively high sample diversity were collected. Microbial DNA amplicon sequencing and mass spectrometry-based untargeted metabolomics show that the CDT microbial ß diversity, as well as the nonvolatile chemical α and ß diversities, is determined by the primary impact factors of geography and manufacturing procedures, in particular, latitude and pile fermentation after blending. A large number of metabolites sharing between CDTs and fungi were discovered by Feature-based Molecular Networking (FBMN) on the Global Natural Products Social Molecular Networking (GNPS) web platform. These molecules, such as prenylated cyclic dipeptides and B-vitamins, are functionally important for nutrition, biofunctions, and flavor. Molecular networking has revealed patterns in metabolite profiles on a chemical family level in addition to individual structures.

Temporal and spatial pattern of endophytic fungi diversity of Camellia sinensis (cv. Shu Cha Zao).

BACKGROUND: The experimental materials were a 60-year-old tea tree (Camellia sinensis cv. Shu Cha Zao; SCZ) (the mother plant) and 1-year-old and 20-year-old plants of SCZ that originated as mother plant cuttings. The aim of this study was to use high-throughput sequencing to study the spatial and dynamic distribution of endophytic fungi in different leaf niches (upper leaves, middle leaves, lower leaves) and rhizosphere soil on tea plants of different ages in the same garden. RESULTS: Ascomycota (83.77%), Basidiomycota (11.71%), and Zygomycota (3.45%) were the dominant fungal phyla in all samples. Cladosporium (12.73%), Zymoseptoria (9.18%), and Strelitziana (13.11%) were the dominant genera in the leaf. Alpha diversity analysis revealed that endophytic communities in leaves differed from those in rhizosphere soil and different leaf niches had similar fungal diversity. Shannon's indices and NMDS analysis indicated significant differences in fungal diversity and composition among the SCZ trees of different ages (p ≤ 0.01). The abundance of Cladosporium and Zymoseptoria decreased with increasing SCZ age, whereas the abundance of Strelitziana increased. CONCLUSIONS: The results illustrate variation in endophytic fungi among different niches on tea plants of different ages. The distribution of endophytic fungi in leaves of C. sinensis shows spatiotemporal variation.

Feature-Based Molecular Networking Analysis of the Metabolites Produced by In Vitro Solid-State Fermentation Reveals Pathways for the Bioconversion of Epigallocatechin Gallate.

Dark teas are prepared by a microbial fermentation process. Flavan-3-ol B-ring fission analogues (FBRFAs) are some of the key bioactive constituents that characterize dark teas. The precursors and the synthetic mechanism involved in the formation of FBRFAs are not known. Using a unique solid-state fermentation system with ß-cyclodextrin inclusion complexation as well as targeted chromatographic isolation, spectroscopic identification, and Feature-based Molecular Networking on the Global Natural Products Social Molecular Networking web platform, we reveal that dihydromyricetin and the FBRFAs, including teadenol A and fuzhuanin A, are derived from epigallocatechin gallate upon exposure to fungal strains isolated from Fuzhuan brick tea. In particular, the strains from subphylum Pezizomycotina were key drivers for these B-/C-ring oxidation transformations. These are the same transformations seen during the fermentation process of dark teas. These discoveries set the stage to enrich dark teas and other food products for these health-promoting constituents.

Positive Effects of the Tea Catechin, (-)-Epigallocatechin-3-Gallate, on Gut Prophenoloxidase and the Survival of Ectropis obliqua (Lepidoptera: Geometridae).

Ectropis obliqua Prout is the main pest of the tea plant Camellia sinensis (L.) O. Kuntze in China, affecting an annual area of more than one million acres. (-)-Epigallocatechin-3-gallate (EGCG) is the major catechin in tea leaves. Here, we show that EGCG is highly efficient in increasing the survival rate of E. obliqua larvae. We also compared the gut peroxidase (PO) activity between EGCG-fed and control larvae. EGCG-fed larvae had significantly greater PO activity levels than control larvae. Western blotting validated these results. Gut PO activity levels of larvae fed an artificial diet gradually decreased and disappeared completely by day 5. We hypothesize that the increased survival rate of EGCG-fed larvae was associated with increased PO activity. This research provides evidence that E. obliqua larvae have adapted to, and may even benefit from, secondary compounds found in tea leaves.

Positive effects of the tea catechin (-)-epigallocatechin-3-gallate on gut bacteria and fitness of Ectropis obliqua Prout (Lepidoptera: Geometridae).

Ectropis obliqua Prout (Lepidoptera: Geometridae) is the most devastating insect pest of tea plants in China and infests thousands of hectares of tea plantations in China annually. (-)-Epigallocatechin-3-gallate (EGCG) is a major phenolic compound in tea leaves and has a strong antibacterial function. Here, we show that EGCG can effectively improve the fitness of E. obliqua larvae and present the reason by which EGCG promotes larval fitness. In this study, we compared the fitness difference among Control, Antibiotic and Treatment of larvae. The fitness of larvae treated with EGCG and antibiotic was similar and better than that of control group. We also demonstrated that EGCG treatment could significantly reduce species richness and abundance of gut bacteria in E. obliqua larvae. Hence that we speculate that EGCG promotes larval fitness and is associated with ECGG antimicrobial activity. In short, our study provides evidence of the E. obliqua larvae have adapted to secondary compounds found in tea leaves, and may even benefit from these compounds. Our study also contributes to a greater understanding of the reason involved in plant-insect interactions.