Immobilization of β-galactosidase onto magnetic poly(GMA–MMA) beads for hydrolysis of lactose in bed reactor

Abstract

In the present study, novel magnetic beads were prepared from glycidylmethacrylate and methylmethacrylate via suspension polymerization in the presence of a cross-linker (i.e. ethylenedimethylmethacrylate). The magnetic poly(GMA-MMA) beads were characterized with scanning electron microscope, FT-IR and ESR spectrophotometers. The reactive character of the epoxy groups allowed the attachment of the amino groups. The aminated magnetic beads were used for the covalent immobilization of beta-galactosidase via glutaric dialdehyde activation. The maximum amount of immobilized beta-galactosidase on the magnetic poly(GMA-MMA) beads was 9.87 mg/g support. The values of Michaelis constants K-m for immobilized beta-galactosidase was significant larger, indicating decreased affinity by the enzyme for its substrate, whereas V-max values were smaller for the immobilized beta P-galactosidase. However, the beta-galactosidase immobilized on the magnetic poly(GMA-MMA) beads resulted in an increase in enzyme stability with time. Optimum operational temperature for immobilized enzyme was 5 degrees C higher than that of the free enzyme and was significantly broader. Finally, a bed reactor with P-galactosidase immobilized was used for hydrolysis of lactose. The enzyme reactor operated continuously at 35 degrees C for 60 h and the immobilized enzyme lost about 12% of its initial activity after this period. (C) 2006 Elsevier B.V. All rights reserved.