Candolleomyces candolleanus P9 from Altay Glycyrrhiza: β-glucosidase-mediated biotransformation

Endophytic fungi establish a symbiotic relationship with their host plants, actively engaging in the hosts' physiological and metabolic processes. They can directly or indirectly transform plant metabolites, thereby playing a crucial role in the host's overall health and functioning. In this study, we isolated and identified an endophytic fungus, Candolleomyces candolleanus P9 strain, which produces β-glucosidase from Ural Glycyrrhizae Radix in Altay, Xinjiang Uygur Autonomous Region, China. In addition, the enzyme production conditions of strain P9 were optimized using a wheat bran concentration of 30.6 g/L, beef extract concentration of 11.2 g/L, inoculum size of 2.6%, pH 7.23, at 30 °C, with shaking at 150 rpm, and a fermentation duration of 6 days. Under these conditions, the β-glucosidase activity of strain P9 increased by 13.6-fold compared to the initial level. On this basis, the efficiency of converting diurea-based urea into diurea-based elements was further optimized. The optimized results were as follows: conversion time 12 h, temperature 37℃, liquiritin concentration 0.8 mg/mL, pH value 7.5, and the conversion rate reached 93.09%. In addition, the antibacterial and antioxidant effects of the fermentation broth of the P9 strain after biotransformation were significantly better than those of commercial β-glucosidase and control group. In summary, fermentation with the β-glucosidase-producing Candolleomyces candolleanus P9 strain is a potential method for converting liquiritin into liquiritigenin of Glycyrrhiza uralensis Fisch.