Highly Efficient Display of Oligomeric Enzymes on Yeast Surface for Enhanced Glycyrrhizin Hydrolysis and Cellulosic Ethanol Production

The subunit dissociation of oligomeric enzymes is a major challenge that limits their practical applications. In this study, yeast-surface-displayed tetrameric β-glucuronidase with a C-terminal anchor protein fusion was found partially dissociated into dimers. The coexpression of free and anchored subunits significantly improved the display efficiency and catalytic activity. Given that oligomeric enzymes may adopt a non-native conformation on the cell surface, the subunit interfaces of surface-displayed β-glucuronidase were in situ characterized using a Förster resonance energy transfer (FRET) strategy, and the tetrameric structure was well maintained in the coexpressed β-glucuronidases. Finally, the coexpression strategy was applied to yeast-surface-displayed oligomeric cellulases, significantly enhancing the activities of tetrameric endoglucanase and dimeric β-glucosidase and the concentration of cellulosic ethanol for the two-enzyme codisplaying strain. This work provides insights into the structure–activity relationship and the efficient utilization of surface-displayed oligomeric enzymes.