Chemically surface modified gel (CSMG): An excellent enzyme-immobilization matrix for industrial processes

Invertase from S. cerevisiae has been immobilized on porous silica matrix, formed using sol–gel chemistry, with surface area of approximately 650 m2/g. The co-condensation of silica sol with 3-aminopropyl(triethoxy)silane produced an amino-chemically surface modified silica gel (N-CSMG) with a very high ligand loading of 3.6 mmol/g SiO2; significantly higher than commercially available matrices. Surface amine groups were activated with glutaraldehyde to produce GA-N-CSMG, and invertase covalently attached by the aldehyde.Invertase was used as a model enzyme to measure the immobilizing character of the GA-N-CSMG material. Using an optimized immobilization protocol, a very high loading of 723 mg invertase per gram GA-N-CSMG is obtained; 3–200-fold higher than values published in literature. The reproducible, immobilized activity of 246,000 U/g GA-N-CSMG is also greater than any other in literature. Immobilized invertase showed almost 99% retention of free enzyme activity and no loss in catalytic efficiency. The apparent kinetic parameters KM and VM were determined using the Michealis–Menten kinetic model. KM of the free invertase was 1.5 times greater than that of the immobilized invertase—indicating a higher substrate affinity of the immobilized invertase. These findings show considerable promise for this material as an immobilization matrix in industrial processes.