Cross-linking of horseradish peroxidase adsorbed on polycationic films: utilization for direct dye degradation.

Horseradish peroxidase (HRP) was immobilized on the polyaniline (PANI) grafted polyacrylonitrile (PAN) films. The maximum HRP immobilization capacity of the PAN-g-PANI-3 film was 221 μg/cm(2). The HRP-immobilized PAN-g-PANI-3 film retained 79 % of the activity of the same quantity free enzyme. The HRP-immobilized PAN-g-PANI-3 film was operated for the decolorization of two different benzidine-based dyes in the presence of hydrogen peroxide. The maximum decolorization grade was obtained at pH 6.0 for both dyes. The HRP-immobilized PAN-g-PANI-3 film was very effective for removal of Direct Blue-53 compared to Direct Black-38 from aqueous solutions. The immobilized HRP exhibited high resistance to proteolysis by trypsin compared to the free counterpart. Immobilized HRP preserved 83 % of its original activity even after 8 weeks of storage at 4 °C, while the free enzyme lost its initial activity after 3 weeks of storage period.