Screening strains for directed biosynthesis of β-d-mono-glucuronide-glycyrrhizin and kinetics of enzyme production

One fungus, tentatively named Penicillium sp. Li-3, was screened to biosynthesize β-d-mono-glucuronide-glycyrrhizin (GAMG), directly. Using glycyrrhizin as elicitor and the sole carbon source, this strain was capable of expressing β-d-glucuronidase, one intracellular enzyme with high substrate specificity. And glycyrrhizin was hydrolyzed directly into GAMG by enzyme from Penicillium sp. Li-3 with high production. It was found that the mol conversion ratio of this reaction was up to 88.45%. Research about kinetics of β-d-glucuronidase production showed that the cell growth and enzyme production of this strain was partial coupled. During the expressing of target enzyme, carbon catabolite repression existed, so only glycyrrhizin was the best carbon source as well as the elicitor. It was found that the surfactant (Tween 80 0.12%) could improve the ability of enzyme production markedly. Under the condition of initial pH 4.8 of the medium and 32 °C of the culture temperature, the maximum enzyme activity of 181.53 U ml−1 was obtained.