Selenium enrichment promotes selenium biotransformation and enhances antioxidant capacity in germination fungi associated with Gastrodia elata.

To investigate the selenium-enrichment capacity of Gastrodia elata germination fungi and the effects of selenium enrichment on their antioxidant function, four germination fungal strains were selected to systematically evaluate selenium accumulation, biotransformation characteristics, selenium distribution patterns, and antioxidant responses through selenium tolerance screening, selenium-enriched cultivation, and functional assessment. The results demonstrated that different germination fungi exhibited distinct responses to exogenous selenium. Among them, strain MFA showed superior selenium tolerance and selenium-enrichment efficiency and was identified as the elite selenium-enriched strain. Selenium enrichment significantly increased both total selenium and organic selenium contents in MFA mycelia, with an organic selenium conversion rate reaching 99.8%. Selenium distribution analysis revealed that selenium was predominantly accumulated in the protein fraction (70.64%), followed by the polysaccharide fraction, whereas only a small proportion was detected in nucleic acids, indicating that absorbed inorganic selenium could be effectively transformed and preferentially incorporated into protein-bound forms. Further investigation showed that selenium enrichment enhanced antioxidant enzyme activities and promoted soluble protein accumulation, while significantly improving the scavenging capacities against DPPH radicals, ABTS⁺ radicals, and hydroxyl radicals. These findings indicate that G. elata germination fungi possess strong abilities for selenium uptake, assimilation, and biotransformation. Selenium enrichment not only facilitates the conversion of inorganic selenium into organically bound forms but also enhances the antioxidant capacity of fungal mycelia. This study systematically elucidates the selenium-enrichment characteristics, biotransformation behavior, and functional responses of germination fungi, providing a theoretical basis for the development of novel selenium-enriched functional fungal resources.