Oriented covalent immobilization of esterase BioH on hydrophilic-modified Fe3O4 nanoparticles

The esterase BioH from Escherichia coli was covalently immobilized onto the surface of the functional magnetic nanosupport in an oriented manner. The surface of the Fe 3 O 4 nanosupport was modified with acyl azide groups or both acyl azide groups and hydroxyl groups. The protein loading of the support was increased from 55 to 99 mg/g by an improvement in hydrophilicity, and the activity retention of the immobilized esterase on the nanosupport was improved by 40% after hydrophilic modification (30% and 70% of the free BioH, respectively). For the BioH immobilized on the hydrophilic-modified nanosupport, the recovery activity remained 80% of the original activity after 10 times of recycling. The catalytic kinetics and thermo-/pH-stability of the immobilized esterase BioH were also determined and compared with those of the free enzyme. The comparatively high activity retention, improved thermo-/pH-stability, and good reusability of the immobilized enzyme indicate that oriented covalent immobilization is an efficient method for immobilizing esterase BioH.