Immobilization of catalases on amidoxime polyacrylonitrile nanofibrous membranes

Amidoxime polyacrylonitrile (AOPAN) nanofibrous membranes were generated by the reaction between electrospun polyacrylonitrile nanofibrous membranes and hydroxylamine hydrochloride. AOPAN nanofibrous membranes were further modified by Fe(III) chelation for immobilizing catalases with coordination bonds. The surface morphologies of the nanofibrous membranes and immobilized catalases were observed by field emission scanning electron microscopy. Chelation of Fe(III) onto AOPAN nanofibrous membranes was studied by the Langmuir isothermal adsorption model. It was found that the maximum amount of coordinated Fe(III) (qm) was 4.5045 mmol g-1 (dry nanofibrous membranes) and the binding constant (Kl) was 0.0698 L mmol-1. The amounts of immobilized enzymes were determined by the method of Bradford. Kinetic parameters were analyzed for both immobilized and free catalases. The value of Vmax (7122.6 mu mol mg-1 min-1) for the immobilized catalases was smaller than that for the free catalases (9203.2 mu mol mg-1 min-1), and the Km for the immobilized catalases was larger. The immobilized catalases showed better resistance to pH and temperature change than the free catalases, and the storage stability of immobilized catalases was higher than that of free catalases. As for reusability, the immobilized catalases retained 71% of their activity after eight repeated uses. (C) 2012 Society of Chemical Industry