Magnetic cellulose nanocrystals: Synthesis by electrostatic self-assembly approach and efficient use for immobilization of papain

Abstract

Novel magnetic cellulose nanocrystals (MCNCs) prepared via electrostatic self-assembly approach were used as magnetic carriers for efficient immobilization of papain and facilitated recovery of this immobilized enzyme. Zeta potential measurements, Fourier transform infrared spectroscopy and Scanning electron microscope were applied to evaluate the forming mechanism and surface structure of MCNCs. Cellulose nanocrystals (CNCs) were successfully combined with cationic polyethyleneimine (PEI) modified Fe₃O₄ nanoparticles (NPs), and the electrostatic interaction between them was a key driving force. The prepared MCNCs were successfully used for the immobilization and separation of papain from the reaction system. When enzyme concentration and pH value of enzyme solution were 0.4 mg mL⁻¹ and 6, respectively, the resultant immobilized enzyme exhibited the highest enzymatic activity about 227 μg min⁻¹ g⁻¹. Better pH and thermo stabilities than those of the free papain were also achieved after immobilizing the enzyme on MCNCs. Furthermore, the immobilized papain manifested enhanced tolerability to three different solvents, namely n-butyl alcohol, n-hexane and [Cnpy][NTf₂], respectively. The prepared MCNCs as the efficient carrier materials have a strong application potential for enzyme immobilization.