Immobilized penicillin G acylase with enhanced activity and stability using glutaraldehyde-modified polydopamine-coated Fe 3 O 4 nanoparticles

In this work, Fe O nanoparticles (NPs) were coated with polydopamine (PDA) to structure Fe O @PDA NPs by the spontaneous oxygen-mediated self-polymerization of dopamine (DA) in an aqueous solution of pH = 8.5. The fabricated Fe O @PDA NPs were grafted by glutaraldehyde to realize the immobilization of penicillin G acylase (PGA) under mild conditions. The carriers of each stage were characterized and investigated by transmission electron microscopy, X-ray diffraction, Fourier transform infrared, and vibrating sample magnetometry. To improve the catalytic activity and stability of immobilized PGA, the immobilization conditions were investigated and optimized. Under the optimal immobilization conditions, the enzyme loading capacity, enzyme activity, and enzyme activity recovery of immobilized PGA were 114 mg/g, 26,308 U/g, and 78.5%, respectively. In addition, the immobilized PGA presented better temperature and pH stability compared with free PGA. The reusability study ensured that the immobilized PGA showed an excellent repeating application performance. In particular, the recovery rate of immobilized PGA could reach 94.8% and immobilized PGA could retain 73.0% of its original activity after 12 cycles, indicating that the immobilized PGA exhibited a high operation stability and broad application potential in the biocatalysis field.