Lactose Hydrolysis by Beta-galactosidase from 'Kluyveromyces lactis' Immobilised on Graphite Surface

The cross-linking immobilisation of beta-galactosidase from 'Kluyveromyces lactis' on graphite surfaces is reported, herein the cross-linking reagent is glutaraldehyde. The Michaelis-Menten constant for both free and immobilised enzyme is measured using ONPG as substrate. The Km (1.7mM) for free enzyme with O-nitrophenyl-B-D-galactopyranoside (ONPG) as substrate is lower than the apparent kinetic constant Kapp (9.3 mM) for immobilised enzyme. On the other hand, Vm for free enzyme and Vapp for immobilised enzyme are 77 imol/min mg protein and 0.009 umol/min mg protein respectively. Thermal deactivation of the immobilised enzyme follows Arrhenius Law. The effect of pH and temperature on enzyme activity is presented as well. Lactose hydrolysis in skim milk are investigated in a continuous enzymatic hydrolysis reactor.