Magnetic carboxylated cellulose nanocrystals for pullulanase immobilization: enhanced enzyme activity and reusability

In the realm of enzyme immobilization, challenges such as decreased activity post-immobilization and insufficient reusability are frequently encountered. In this paper, carboxylated cellulose nanocrystals (CNCs) obtained from deep eutectic solvent (DES) pretreatment were used for the synthesis of magnetic CNCs (MCNCs), which served as a carrier for enzyme immobilization. The results demonstrated that the hydrophilic carboxyl groups introduced on MCNCs by DES pretreatment are beneficial for enhancing the activity and reusability of immobilized pullulanases. Based on activity and reusability, we further optimized the immobilization conditions and catalytic temperature. Under the optimal conditions, compared to free enzymes, the relative activity of immobilized pullulanase increased to 162.24%, and it maintained 95.07% of its initial activity after 15 cycles of reuse. Overall, our findings highlight the potential of immobilizing pullulanase on MCNC to enhance enzyme activity and reusability.