Screening and bioconversion of glycyrrhizin of Glycyrrhiza glabra root extract to 18β-glycyrrhetinic acid by different microbial strains

Objective: The objective of the present study is to perform screening of different microorganisms (7 bacteria and 14 fungi) for conversion of glycyrrhizin (GL) to 18β-glycyrrhetinic acid (GA). Penicillium chrysogenum produced the highest concentration of β-glucuronidase enzyme (61 U/mL) and produced GA of 52 μg/mL while E. coli produced the highest β-glucuronidase of 376 U/mL with GA concentration of 2.1 μg/mL. Materials and Methods: Submerged and solid state biotransformation of GL was carried out. To 9.0 mL of bacterial supernatant, 1.0 mL 0.2% w/v of aqueous Glycyrrhiza glabra root extract was added and incubated at 37°C for 24 h. β-glucuronidase activity was measured and high-performance liquid chromatography analysis was carried out. Results and Discussion: Induced-Escherichia coli produces 2.1 μg/mL of GA with an enzyme activity of 376 U/mL which shows that the enzyme has a potential biotransformation capability. Rhizopus oryzae and P. chrysogenum have the potential ability to biotransform GL to GA with 2.6 μg/mL and 61 μg/mL of GA with enzyme activity of 569 U/mL and 61 U/mL, respectively. Conclusions: G. glabra roots containing GL can be hydrolyzed by microbial β-glucuronidase enzyme under sub-merged fermentation (SmF). β-glucuronidase, an enzyme of E. coli, was found to be the best microbial source of enzyme which biocatalyzed the reaction than fungal strain under SmF.