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

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.