Aspartic acid introduce the functional amine groups on the surface of superparamagnetic Fe(OH)3@Fe3O4 nanoparticles for efficient immobilization of Penaeus vannamei protease.

In this study, we synthesized super magnetic Fe(OH)3@Fe3O4 nanoparticles (SPIONs) by the co-precipitation method and introduction of amine groups via chemisorption of L-aspartic acid (LAA) on the surface of SPIONs. Penaeus vannamei protease (PVP) was immobilized onto amine-functionalized supermagnetic nanoparticles (ASPIONs), and conditions affecting PVP immobilization were investigated. PVP immobilized onto ASPIONs exhibited shifts in both working optimum pH and temperature with an increase from pH 7 to pH 8, and increased optimum temperature by 10 °C compared to free enzyme. Similarly, the thermal, pH, and storage stabilities of the immobilized PVP were superior to those of free form of the enzyme. In comparison to the free enzyme, the immobilized enzyme was reusable for 15 cycles while retaining 73% of its initial activity. The Michaelis-Menten kinetic constant (Km) and maximum reaction velocity (Vmax) for free PVP were 2.3 µM and 88 µM min-1, respectively, whereas Km and Vmax values of immobilized enzyme were 2.5 µM and 85 µM min-1, respectively. These results indicated that immobilized PVP was efficient in terms of catalytic activity and can be applied to continuous casein processing applications in the different industries.