Tea Rhizosphere Fungi Show Ability to Break Down Tannin Compounds

Fungi living in the soil around tea plant roots can consume oligoproanthocyanidins, a group of plant tannins that cause astringency in foods and limit the use of agricultural residues in animal feed, according to a study published in npj Science of Food.

Researchers isolated five filamentous fungal strains from the rhizosphere of tea plants (Camellia sinensis) growing in habitats naturally enriched with proanthocyanidins. In laboratory cultures, all five strains were able to use oligoproanthocyanidins as their sole carbon source, growing to levels comparable to those reached on sucrose-based media.

When the fungi were grown in submerged fermentation with the tannins, the cultures showed measurable changes in pH and color, which the authors used as indicators of ongoing metabolism. Analysis of the cultures revealed eight fungal metabolites with nutritional and antibacterial properties. Among these was schizostatin, produced by the edible mushroom species Schizophyllum commune, strain ScCYS1063.

To understand the chemistry behind the degradation, the team applied non-targeted metabolomics, which indicated that oligoproanthocyanidin breakdown was connected to the fungi’s central energy metabolic pathways rather than to a single isolated detoxification route.

Transcriptomic analysis added a second layer of insight. The data suggested a pattern in which proanthocyanidins could act as a carbon source capable of fueling fumagillin biosynthesis, and they revealed class-level transcriptional responses in genes encoding monooxygenases, cytochrome P450 enzymes, and dioxygenases, enzyme families often involved in oxidizing complex plant molecules.

The researchers also recovered extracellular proteins from the fungal cultures and tested their activity directly. These proteins effectively degraded procyanidin B2, a common dimeric proanthocyanidin, supporting the possibility of controlled enzymatic processes for breaking down oligoproanthocyanidins outside living cells.

The findings matter because incomplete degradation of proanthocyanidins is a persistent problem for the food industry: the compounds cause astringency, reduce nutrient bioavailability, and hinder the use of tannin-rich agricultural residues as feed. Microbial or enzymatic treatments that dismantle these molecules could offer new processing options.

The study is framed as an early-stage exploration of biotransformation potential rather than a demonstration of an industrial process. The work was carried out with isolated strains in laboratory fermentation, and the reported metabolites and enzyme activities describe what the fungi did under those specific conditions.

More broadly, the authors highlight the value of mining microbial communities from the tea rhizosphere, an environment where plants and microbes coexist with high levels of tannins, as a source of organisms and enzymes for transforming natural metabolites. The team suggests that such communities could yield novel solutions for food applications, building on the identified fungal strains and their extracellular protein repertoire.

Subject of Research: Integrated metabolomic and transcriptomic analysis of oligoproanthocyanidins biotransformation by rhizosphere filamentous fungi from tea plant (Camellia sinensis)

Article Title: Integrated metabolomic and transcriptomic analysis of oligoproanthocyanidins biotransformation by rhizosphere filamentous fungi from tea plant (Camellia sinensis)

Article References: Liang, S., Zou, C., Xu, L., Ma, B., Gao, Y., Yin, J.-F., Jin, P., & Xu, Y.-Q. (2026). Integrated metabolomic and transcriptomic analysis of oligoproanthocyanidins biotransformation by rhizosphere filamentous fungi from tea plant (Camellia sinensis). npj Science of Food. https://doi.org/10.1038/s41538-026-01227-2

Image Credits: AI Generated

DOI: 10.1038/s41538-026-01227-2

Keywords: Integrated, metabolomic, transcriptomic, analysis, oligoproanthocyanidins, biotransformation, rhizosphere, filamentous, fungi, plant, Camellia, sinensis