Covalent immobilization of Kluyveromyces fragilis β-galactosidase on magnetic nanosized epoxy support for synthesis of galacto-oligosaccharide.

The novel magnetic nanobeads with epoxy groups on the surface were prepared from glycidyl methacrylate (GMA), ethylene glycol dimethacrylate (EGDMA) and hydroxyethyl methacrylate (HEMA) via emulsifier-free emulsion polymerisation, and they were characterized by scanning electron microscopy and vibrating sample magnetometer. The magnetic poly(GMA-EDGMA-HEMA) nanobeads were used as support for covalent immobilization of Kluyveromyces fragilis β-galactosidase, the maximum amount enzyme attached onto the support was 145.6 mg/g with activity recovery of 72.6%. The loading capacity of this novel support for K. fragilis β-galactosidase was improved 2.6-folds compared with Eupergit® C (commercial epoxy support). The immobilized K. fragilis β-galactosidase exhibited high catalytic activity for the reaction of galacto-oligosaccharide (GOS) synthesis, and a total of 2,240 g GOS were produced per gram of immobilized enzyme during consecutive batch reaction of 10 times. The immobilized biocatalyst retained 81.5% of its original activity after 10 reaction cycles.