Enhancement of the catalytic activity and stability of immobilized aminoacylase using modified magnetic Fe3O4 nanoparticles

Aminoacylase (EC 3.5.1.14) was immobilized via covalent bonding to magnetic iron oxide (Fe3O4) nanoparticles with 3-(aminopropyl)triethoxysilane (APTES) modification. Magnetic Fe3O4 nanoparticles were prepared by chemical co-precipitation, controlling n(Fe3+):n(Fe2+) = 2:1 and c(Fe3+) + c(Fe2+) = 0.3 mol/L. The nanoparticles modified with APTES were characterized by SEM and FT-IR. The results showed that the optimal nanoparticle concentration, glutaraldehyde concentrations, crosslink time and immobilization time are 8 mg/mL, 1.0%, 1 h, and 1.5 h, respectively. Moreover, the optimal temperature, pH and thermostability of free and immobilized enzymes were compared. The properties of repeatedly used immobilized aminoacylase were also investigated.