Isolation, identification and microbial transformation of endophytic fungi Colletotrichum queenslandicum KJT-1 of Tinospora sinensis postprint

Abstract: To fully develop the endophytic fungal resources of Tinospora sinensis and obtain strains with microbial transformation capabilities for the host medicinal material, this study employed a tissue isolation method and ITS sequence analysis to identify the isolated endophytic fungi and conduct microbial transformation research. The bioactivity and chemical composition differences of the extracts before and after microbial transformation were analyzed and evaluated through antibacterial experiments, DPPH radical scavenging assays, and liquid chromatography-mass spectrometry (LC-MS) techniques. The results were as follows: (1) An endophytic fungus was isolated and identified as Colletotrichum queenslandicum from Tinospora sinensis, which demonstrated microbial transformation capabilities towards the host medicinal material. (2) The extracts of T. sinensis before microbial transformation had no inhibitory effect on the tested strains. Howeever, after microbial transformation, the n-butanol extract of T. sinensis had inhibitory effect on Staphylococcus aureus, with a minimum bactericidal concentration of 31.3 g·mL-1. (3) The DPPH free radical scavenging ability of crude extract, n-butanol and ethyl acetate extract was decreased compared with that before transformation, while the petroleum ether extract exhibited an enhanced scavenging ability compared with that before transformation. (4) A total of 33 and 23 compounds were identified and characterized from the n-butanol extracts of Tinospora sinensis before and after microbial transformation, respectively, indicating the changes in chemical composition. This study isolated and obtained an endophytic fungus with microbial transformation capabilities of the T. sinensis, providing theoretical support for research on its efficient utilization and biotransformation.