Immobilization of β-galactosidase on graphite surface by glutaraldehyde Original Research Article

In this study, β-galactosidase from Kluyveromyces lactis was immobilized onto graphite surface using glutaraldehyde as the cross-linking reagent with the specific activity yield of 17% and 25%, while the enzyme loading was 1.8 and 1.1 U/cm2 of the graphite external surface area, respectively. The activity yield was decreased with the increase of the enzyme loading. The Michaelis–Menten kinetics parameters, Km and Vm for the free enzyme were estimated to be 1.74 mM and 77.34 μmol o-nitrylphenol min−1 mg−1 enzyme, respectively. The Km value of the immobilized enzyme was found to be of five folds of the free enzyme. Lactose hydrolysis at concentrations of 5% (w/v) by the immobilized enzyme was also investigated. The degree of lactose hydrolysis was approximately 70% at 37°C over a period of 3 h. The immobilized enzyme showed a good storage and operational stability.