Fermentation-Based Production and Immobilization of β-Glucuronidase From Talaromyces pinophilus Li-93 for Efficient Bioconversion of Glycyrrhizin

Glycyrrhizic acid and its derivatives are a crucial class of glycoside terpenoids with significant pharmaceutical and food industry applications. The biotransformation of glycyrrhizin (GL) into glycyrrhetic acid 3-O-mono-β-D-glucuronide (GAMG) and glycyrrhetinic acid (GA) can enhance the production of these valuable compounds. This study aimed to develop strategies to improve the catalytic and operational stability of β-glucuronidase from wild-type Talaromyces pinophilus Li-93 previously known as Penicillium purpurogenum Li-3 (w-PGUS) for efficient GL hydrolysis. Whole cells of T. pinophilus Li-93 expressing w-PGUS were capable of directly converting GL into GAMG. To enhance enzyme stability and reusability, three polymeric supports polyurethane foam (PUF), loofah sponge (LS), and polyvinyl chloride (PVC) were evaluated for immobilization of w-PGUS from the fermentation medium. Among these, PUF was the most effective immobilization support, yielding superior immobilization efficiency, GAMG production, and biomass retention. Under optimized conditions (1% PUF, 1.5 g/L w-PGUS inoculum, pH 5.0, 36 °C, 180 rpm), a 67.10% immobilization efficiency was achieved within 72 h. The PUF-immobilized w-PGUS retained 37.51% of its initial activity after 10 repeated batch reactions, whereas free w-PGUS retained only 6.21%. Additionally, the storage stability of immobilized w-PGUS was significantly higher (40.22%) than that of free w-PGUS (14.74%) after 30 days. The superior durability, cost-effectiveness, and enhanced operational and storage stability of PUF-immobilized w-PGUS highlight its potential for large-scale biosynthesis of GAMG.