Polyacrylonitrile membrane surfaces were modified with chemical polymerization of conductive polyaniline. The effect of aniline concentration on the grafting efficiency was investigated As the amount of grafted PANI increased on the PAN membrane, the electrical resistance of composite membrane decreased Composite (PAN/PANI)-1-5 membrane were used for reversible immobilization of GOD. The immobilization efficiency and the activity of the immobilized GOD were increased with increasing PANI contents of the composite membrane. The maximum amount of immobilized enzyme into composite PAN/PANI-5 membrane containing 2.1% PANI was about 251 mu g/cm(2) Immobilized GOD exhibited 66% of its original activity even after two months of storage at 4 degrees C while the free enzyme lost its initial activity after three weeks (C) 2010 Elsevier Ltd. All rights reserved