Fungal community succession and major components change during manufacturing process of Fu brick tea

Abstract

Fu brick tea is a unique post-fermented tea product which is fermented with microorganism during the manufacturing process. Metabolic analysis showed that most metabolites content were decreased during the manufacturing process of Fu brick tea, except GA (gallic acid). Illumina MiSeq sequencing of ITS gene amplicons was applied to analyze the fungal community succession. The genera Aspergillus, Cyberlindnera and Candida were predominant at the early stage of manufacturing process (from "primary dark tea" to "fermentation for 3 days"), but after the stage of "fermentation for 3 days" only Aspergillus was still dominated, and maintain a relatively constant until to the end of manufacturing process. The effects of metabolites on the structure of the fungal community were analyzed by redundancy analysis (RDA) and variation partitioning analysis (VPA). The results indicated that GCG (gallocatechin gallate), EGCG (epigallocatechin gallate) and GA as well as the interactions among them were the most probably ones to influence, or be influenced by the fungal communities during the fermentation process of Fu brick tea. This study revealed fungal succession, metabolite changes and their relationships, provided new insights into the mechanisms for manufacturing process of Fu brick tea.

Figure 1

Metabolite changes during manufacturing process of Fu brick tea. water extract (WE), soluble sugar (SS), flavonoid (FLA), organic acid (OA), tea polyphenol (TP), amino acid (AA), gallic acid (GA), caffeine (CAF), epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), gallocatechin gallate (GCG), epicatechin (EC), catechins (C). *Indicated that the significance <0.05, compared with S1; **indicated that the significance <0.01, compared with S1.

Figure 2

NMDS (A) and Venn diagram analysis (B) of fungal communities in samples during manufacturing process of Fu brick tea.

Figure 3

Fungal taxonomic compositions showing the fungal successions at phylum (A), order (B) and genus (C) level during manufacturing process of Fu brick tea. The taxonomic abundance <1% were classified into “others”. Phylum level (A), order level (B), genus level (C).

Figure 4

RDA and VPA showing the correlations between fungal structure and metabolites concentrations during manufacturing process of Fu brick tea. Ordination diagram of RDA (A). Variance decomposition of VPA (B). Gallic acid (GA), epigallocatechin gallate (EGCG), gallocatechin gallate (GCG). Red arrow indicated the metabolite variance significant effect on the fungal community structure (P < 0.05).