title: Chemically surface modified gel (CSMG): an excellent enzyme-immobilization matrix for industrial processes.
abstract: Invertase from S. cerevisiae has been immobilized on porous silica matrix, formed using sol-gel chemistry, with surface area of approximately 650 m(2)/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 SiO(2); 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 K(M) and V(M) were determined using the Michealis-Menten kinetic model. K(M) 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.
authors.affiliation: Department of Chemical Engineering, A. James Clark School of Engineering, University of Maryland, College Park, MD 20742, United States.
authors.forename: Allan E
authors.initials: AE
authors.lastname: David
authors.forename: Nam Sun
authors.initials: NS
authors.lastname: Wang
authors.forename: Victor C
authors.initials: VC
authors.lastname: Yang
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Yang
mesh_terms: D002617:Chemical Industry / Q000379:methods*; D004795:Enzyme Stability; D004800:Enzymes, Immobilized / Q000378:metabolism* / Q000493:pharmacokinetics / Q000528:radiation effects; D005976:Glutaral / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008962:Models, Theoretical; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D058428:Silica Gel; D012822:Silicon Dioxide / Q000737:chemistry* / Q000378:metabolism; D013055:Spectrophotometry, Infrared; D013501:Surface-Active Agents / Q000138:chemical synthesis*; D013696:Temperature; D013818:Thermogravimetry / Q000379:methods; D043324:beta-Fructofuranosidase / Q000378:metabolism / Q000493:pharmacokinetics / Q000528:radiation effects
chemical_list: D004800:Enzymes, Immobilized; D013501:Surface-Active Agents; D058428:Silica Gel; D012822:Silicon Dioxide; D043324:beta-Fructofuranosidase; D005976:Glutaral