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

Incomplete degradation of proanthocyanidins (PAs) causes astringency, reduces nutrient bioavailability in foods, and hinders the feed use of agricultural residues, posing a critical challenge to the food industry. Herein, we explored the potential of tea plant rhizospheric fungi from long-term PAs-enriched habitats to degrade oligoproanthocyanidins (OPC). The five isolated fungal strains were capable of utilizing OPC as a carbon source and exhibited growth comparable to that observed in sucrose-based media. Under submerged fermentation, these fungi metabolized OPC, resulting in changes in pH and color that served as indicators. This process yielded eight fungal metabolites with nutritional and antibacterial properties, notably schizostatin, which was produced by the edible mushroom Schizophyllum commune ScCYS1063. Non-targeted metabolomics revealed that OPC degradation was linked to central energy metabolic pathways. Furthermore, transcriptomic analysis indicated the pattern of PAs as a carbon source capable of fueling fumagillin biosynthesis, triggering class-level transcriptional responses of genes encoding monooxygenases, cytochrome P450S, and dioxygenases. Recovered extracellular proteins effectively degraded procyanidin B2, supporting the potential for controlled enzymatic processes to break down OPC. This study highlights the value of harnessing microbial communities from tea rhizosphere to advance biotransformation of natural metabolites, offering novel solutions for the food industry.