Enhanced Catalysis of Ibuprofen Esterification by CALB Immobilized on Functionalized Magnetic Nanoparticles

This study investigates the performance of lipase B from Candida antarctica (CALB) immobilized on magnetic Fe3O4 nanoparticles (MNs) for the enantioselective esterification of racemic ibuprofen. The nanoparticles were synthesized by co-precipitation and subsequently functionalized with γ-aminopropyltriethoxysilane (APTS) and glutaraldehyde (GLU) to provide reactive aldehyde groups for enzyme attachment. CALB was covalently immobilized onto the activated support, and the resulting biocatalyst was characterized by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR), confirming successful functionalization and enzyme immobilization. The effects of stirring speed (20-250 rpm), enzyme loading (50‑650 U p-nitrophenyl butyrate (p-NPB) g–1), contact time (0.5-5 h), glutaraldehyde concentration (2.5-25%), and sodium dodecyl sulfate (SDS, 0.23%) addition were systematically evaluated. The optimal immobilization conditions (45 rpm, 25 °C, pH 7.0, and 1 h of contact with an enzyme load of 80 U p-NPB g–1) yielded an immobilization efficiency of 53% and an immobilized enzyme activity of 29.1 U g–1. The MNs-CALB derivative exhibited excellent thermal stability (20-fold higher half-life than the soluble enzyme) and was successfully applied in the esterification of racemic ibuprofen with 1-propanol in cyclohexane, preferentially producing the (R)-(−)-ibuprofen propyl ester. Molecular docking simulations supported these results by demonstrating favorable interactions between the (R)-enantiomer and CALB’s catalytic triad (Ser105-His224-Asp187). These findings highlight the potential of magnetically recoverable nanobiocatalysts as efficient, stable, and enantioselective systems for green and sustainable synthesis of chiral pharmaceuticals.