Reversible immobilization of a thermophilic β-galactosidase via ionic adsorption on PEI-coated Sepabeads

The immobilization of the enzyme beta-galactosidase from Thermus sp. T2 was performed via ionic adsorption onto two different supports: a new anionic exchanger resin, based on the coating of Sepabeads internal surfaces with polyethylenimine (PEI) polymers (M-w 25,000), and conventional DEAE-agarose. Immobilization proceeded very rapidly in both cases, but the adsorption strength was much higher in the case of PEI-Sepabeads than in DEAE-supports at both pH 5 and 7 (e.g. at pH 7 and 0.4 M NaCl, less than 5% of enzyme was eluted from PEI-support while more than 70% protein was eluted from DEAE-agarose). Interestingly, the PEI-derivatives remained almost fully active at pH 5 and 7 after several weeks of incubation at 50 degreesC, conditions that allows the hydrolysis of lactose in milk coupled with the antimicrobial treatment usually performed. (C) 2002 Elsevier Science Inc. All rights reserved.