Glucoamylase was immobilized onto chemically synthesized polyaniline after activation with glutaraldehyde (PANIG). The immobilized glucoamylase (PANIG-GA) presented better performance than free enzyme when submitted to heat treatment, showing a 10degreesC decrease on the optimal assay temperature. The pH profile of the immobilized and free enzyme revealed similar behaviour, although PANIG-GA exhibited higher stability in the alkaline range (from pH 8.0 to 10). The K-M value of free enzyme for starch (4.76 mg rnL(-1)) was higher than that of the immobilized glucoamylase (0.43 mg mL(-1)) whereas V-max was lower for the immobilized glucoamylase (0.95 mumol min(-1)) preparation than free enzyme (8.58 mumol min(-1)). Thin layer chromatography (TLC) showed that no changes was observed between free and immobilized enzyme starch hydrolysis products. (C) 2004 Published by Elsevier Ltd.