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 Fe3O4 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.