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

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 (CaCl) and 3-aminopropyltriethoxysilane (APTES). In this method, sodium alginate solution containing enzyme was simply dripped into a crosslinker solution containing CaCl 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 Ca 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 CaCl 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.