Efficient biosynthesis of glycyrrhetic acid 3-O-mono-β-d-glucuronide (GAMG) in water-miscible ionic liquid by immobilized whole cells of Penicillium purpurogenum Li-3 in alginate gel

• Various ILs were used to enhance the activity of whole-cell biocatalyst (w-PGUS).
• Hydrophilic IL [BMIM]BF4 rectified the catalytic efficiency of immobilized w-PGUS.
• Higher GAMG yield was achieved by the combination of immobilized w-PGUS and IL.
• High operational stability of immobilized w-PGUS was found in IL medium.

Five immobilizing materials were investigated for the catalytic efficiency of whole cells of Penicillium purpurogenum Li-3 (w-PGUS) and alginate gel was found the best polymer for the biotransformation of glycyrrhizin (GL) into glycyrrhetic acid 3-O-mono-β-d-glucuronide (GAMG). The activity of compositionally optimized w-PGUS alginate beads was examined in different ionic liquids (ILs). The 30% (v/v) hydrophilic IL [BMIM]BF4 in reaction mixture exhibited an explicit biocompatibility with alginate support; consequently aggrandized the catalytic efficiency of the immobilized w-PGUS compared with pure buffer and ILs media. The optimal biotransformation conditions of the immobilized w-PGUS were evaluated and compared with buffer and IL co-solvent media: including w-PGUS beads concentration (70 g/l vs. 80 g/l), substrate concentration (5 mM vs. 4 mM), temperature (45 °C vs. 45 °C), pH (5.4 vs. 5.6), and shaking speed (180 rpm vs. 160 rpm). Under the optimized conditions; the yield of GAMG was 2.62 g/l after 62 h in IL co-solvent medium compared to 2.34 g/l after 72 h in buffer medium. The immobilized w-PGUS also retained 45.80% and 18.13% of their original activity in IL co-solvent and buffer media respectively; after ten repeated batches displaying high operational stability for GL biotransformation.