title: Evaluation of magnetic polymer micro-beads as carriers of immobilised biocatalysts for selective and stereoselective transformations.
abstract: The kinetic, selective and stereoselective properties of enzyme immobilised on magnetic polymer beads with diameters in the range 1 microm was studied with penicillin amidase from E. coli. The enzyme was immobilised on epoxy and glutaraldehyde-activated poly(vinyl alcohol), poly(methylmetacrylate) and poly(vinyl acetate-divinylbenzene) magnetic beads. The amount of covalently bound active protein was dependent on the chemical modification of the matrix and increased at higher ionic strength of the immobilisation buffer. The small size of the magnetic beads, that reduces mass transfer limitations, and the decreased charge density in the electric double layer resulted in lower apparent Km values and higher efficiency for benzylpenicillin hydrolysis, higher stereoselectivity in condensation of R-phenylglycine amide with S- and R-Phe and in hydrolysis of racemic phenylacetyl-Phe and higher selectivity in kinetically controlled synthesis of cephalexin compared to the enzyme immobilised on larger and porous carriers.
authors.affiliation: Forschungszentrum Karlsruhe-in der Helmholtz Gemeinschaft, Institut für Technische Chemie, Bereich Wasser- und Geotechnologie, Hermann von Helmholtz Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Bozhinova
authors.forename: B
authors.initials: B
authors.lastname: Galunsky
authors.forename: G
authors.initials: G
authors.lastname: Yueping
authors.forename: M
authors.initials: M
authors.lastname: Franzreb
authors.forename: R
authors.initials: R
authors.lastname: Köster
authors.forename: V
authors.initials: V
authors.lastname: Kasche
mesh_terms: D001665:Binding Sites; D001709:Biotechnology / Q000379:methods*; D002384:Catalysis; D002506:Cephalexin / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D004800:Enzymes, Immobilized / Q000737:chemistry* / Q000494:pharmacology; D004926:Escherichia coli / Q000378:metabolism; D005976:Glutaral / Q000737:chemistry; D006579:Heterozygote; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D008280:Magnetics; D010399:Penicillin Amidase / Q000737:chemistry; D010400:Penicillin G / Q000737:chemistry; D011108:Polymers; D011506:Proteins / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D004800:Enzymes, Immobilized; D011108:Polymers; D011506:Proteins; D010399:Penicillin Amidase; D002506:Cephalexin; D010400:Penicillin G; D005976:Glutaral