Promoting effect of licorice extract on induction of β-glucuronidase in Penicillium purpurogenum Li-3

Penicillium purpurogenum Li-3, a fungus producing β-glucuronidase (PGUS), can convert glycyrrhizin (GL) to glycyrrhetinic acid monoglucuronide (GAMG) when grown in medium with GL as the sole carbon source. In order to improve the conversion rate of GL and the yield of GAMG, licorice extract (LE) was added as an inducer to enhance the production of GAMG by the PGUS. In this work, the influence of LE on the conversion rate of GL to GAMG was studied. When the Penicillium purpurogenum Li-3 was grown in the medium containing LE and GL (concentration ratio of LE to GL was 2:3), the conversion rate of GL was 84.12% with 38.18% increase and the yield of GAMG was 80.47% with 37.18% increase, comparing with to the medium only containing GL at 48 h. The enzyme activity of β-glucuronidase was also enhanced from 22.4 U/mL to 82.3 U/mL, which increased up to about 3.67 fold. The results showed that LE could significantly improve the induced expression level of PGUS.