Keywords: &, #946, -galactosidase, ionic immobilisation, polyethylenimine supports, reversible immobilisation, Aspergillus oryzae, high lactose conversion, whey, PEI coating
Polyethylenimine coated agarose supports, for the reversible immobilisation of β-galactosidase from Aspergillus oryzae
Immobilised enzymes for industrial applications should be very active and operationally stable. Reversible binding, if possible, is desirable to allow matrix reuse. Usually these aims come into conflict: strong binding may imply low expressed activity and poor reversibility. Immobilisation of Aspergillus oryzae β-galactosidase to conventional ionic exchangers is efficient but the derivatives exhibit noticeable enzyme leakage when used for the hydrolysis of lactose from whey. This problem can be avoided by covalent cross-links to the matrix, at the expense of losing reversibility. We have optimised the conditions for polyethylenimine (PEI)-coating of agarose supports to achieve a β-galactosidase derivative that allows a high lactose conversion from whey in a steady bed-reactor with no enzyme leakage, together with good elution properties. Therefore, PEI-coating appears to be a very suitable strategy to convert the agarose surface to an adequate support for a reversible, but strong and non-distorting, ionic protein immobilisation.