Synthesis and characterization of surface-functionalized paramagnetic nanoparticles and their application to immobilization of α-acetolactate decarboxylase

In this paper, a facile paramagnetic Fe3O4@SiO2-NH2 nanoparticles (PMN Fe3O4@SiO2-NH2 NPs) have been successfully synthesized and characterized, which were applied to alpha-acetolactate decarboxylase (alpha-ALDC) immobilization using 1, 1'-carbonyldiimidazole (CDI) as the covalent reagent. The synthesized nanoparticles exhibited satisfactory paramagnetic under magnetic field, high single-crystalline and abundant amino groups on the surface. The alpha-ALDC loading capacity onto nanoparticles was 48.70 +/- 1.25 mu g/mg carrier and the activity of retained alpha-ALDC remained 69.39 +/- 1.16% in comparison with free alpha-ALDC. Enzyme kinetics analysis showed that immobilized alpha-ALDC had lower affinity to its substrate than that of free alpha-ALDC based on higher Km and little lower limax of immobilized alpha-ALDC. After storage at 4 degrees C in disodium hydrogen phosphate and citric acid (DHPCA) buffer (20 mM, pH 6) for 14 days, immobilized alpha-ALDC retained 65.35% of its initial activity, while the activity of free alpha-ALDC only kept 39.22% in the same conditions. After 5 times re-use, immobilized alpha-ALDC still retained 31.03% of its initial activity for preventing diacetyl production. (C) 2015 Elsevier Ltd. All rights reserved.