Esterase-Immobilized Sea-Urchin-Like Fe3O4 Nanoparticles for Chloramphenicol Palmitate Synthesis

Mostly, enzyme activity is greatly reduced after immobilization due to unfavourable conformational change occurred during the immobilization procedure. Herein, we report a novel magnetic nanoparticle-based platform for Bacillus altitudinis esterase (EstBASΔSP) immobilization using dialdehyde starch (DAS) as a molecular glue. First polydopamine (PDA) was coated on the surface of Fe 3 O 4 nanoparticles (Fe 3 O 4 NPs) with a controllable thickness. Thereafter, PDA-functionalized Fe 3 O 4 NPs were modified with dialdehyde starch (DAS) to provide the aldehyde groups, which was employed as a glue to further fix the EstBASΔSP on particle surface via covalent bonding, resulting in the formation of a sea-urchin-like esterase-immobilized magnetic nanoparticle. The obtained nanoparticles (Fe 3 O 4 @PDA/DAS) achieved an enzyme load of 162.72 mg/g and retained 65.7% of its specific enzyme activity, demonstrating better thermal and storage stability compared with the “polydopamine-coated” nanoparticles (Fe 3 O 4 @PDA) and free EstBASΔSP. In addition, in a chloramphenicol palmitate synthesis, the immobilized esterase (EstBASΔSP-Fe 3 O 4 @PDA/DAS) gave 99% conversion and purity in 21 h (chloramphenicol: 0.15 M, enzyme dosage: 50 mg/mL) and retained over 80% of its activity after 12 cycles. This study provides a general strategy for immobilizing enzyme on nanoparticles and employs them as a novel platform for enzyme-mediated biocatalytic reaction. Graphical Abstract