Facile preparation of aminosilane-alginate hybrid beads for enzyme immobilization: Kinetics and equilibrium studies

Abstract

A simple, facile and potential platform for enzyme immobilization using alginate-based beads has been demonstrated by simultaneous gelation and modification of alginate using calcium chloride (CaCl2) and 3-aminopropyltriethoxysilane (APTES). In this method, sodium alginate solution containing enzyme was simply dripped into a crosslinker solution containing CaCl2 and APTES, leading to the formation of APTES-alginate hybrid beads (AP-beads). The optical observation, FT-IR analysis and amino group measurements provided evidence that APTES was successfully adsorbed to the alginate chain via electrostatic interaction. On the assumption that the binding of Ca2+ ion to polymannuronate residues of alginate via bidentate bridging coordination is competitive with APTES, the equilibrium isotherm and kinetics for the adsorption of APTES to AP-beads was found to follow extended Langmuir isotherm in binary system. Formate dehydrogenase (FDH) as a model enzyme was successfully immobilized in AP-beads and the immobilization yield of ca. 100% could be achieved under optimal conditions of CaCl2 and APTES concentrations in crosslinker solution. Furthermore, the AP-beads were reused efficiently for 9 cycles without loss of FDH activity. The above results demonstrated that AP-beads were effective support for enzyme immobilization.