Semi-solid-state fermentation of Polygonum cuspidatum roots by a novel endophytic fungus Penicillium rubens with capabilities of cell wall hydrolysis and polydatin deglycosylation to improve the yield of high-value resveratrol

Resveratrol (a high-value natural polyphenolic compound with numerous pharmacological activities) is predominantly present in the form of the glycoside polydatin in Polygonum cuspidatum roots. In this study, a novel endophytic fungus, Penicillium rubens, capable of producing both cellulase (0.71 ± 0.09 U/mL) and β-glucosidase (4.35 ± 0.38 U/mL) for cell wall hydrolysis and polydatin deglycosylation, was used to ferment P. cuspidatum roots to improve the yield of valuable resveratrol. Results showed that the semi-solid-state fermentation (SSSF) using the homogeneous cultures of P. rubens was the appropriate strategy to obtain a higher yield of resveratrol from P. cuspidatum roots. Under the optimal fermentation conditions (temperature 30 °C, inoculation dose 4.0 mL/g, and time 72 h), the yield of resveratrol (19.95 ± 0.83 mg/g DW) in P. cuspidatum roots fermented by P. rubens was 19.18-fold higher than that in the unfermented control (1.04 ± 0.47 mg/g DW). Moreover, the digestibility of P. cuspidatum roots by P. rubens in terms of dry matter weight and cellulose content was 40.04% and 21.91%, respectively. Scanning electron microscope observation indicated that P. rubens fermentation could effectively disrupt the cell walls of P. cuspidatum roots, thus contributing to the release of more polydatin for deglycosylation. In addition, the extracts of P. cuspidatum roots fermented by P. rubens exhibited higher antioxidant and antibacterial activities compared with those of the unfermented control. The economic analysis showed that the benefit of SSSF approach for resveratrol production was much greater than that of the unfermented control. Overall, this study proposed a cost-effective SSSF method using the novel P. rubens to obtain bioactive resveratrol from P. cuspidatum roots, which had promising potential in the pharmaceutical, nutraceutical, and cosmetic industries.