Isoamylase, a starch debranching enzyme capable of hydrolyzing alpha-1,6-glucosidic linkage, was immobilized on CM-cellulose and chitin. The immobilization on chemically modified CM-cellulose (CM-cellulose azide) resulted in a specific activity of 1422 U/g-CMCI (CM-cellulose-isoamylase), 24% activity retention, and an optimal pH of 4.0. The immobilization of isoamylase on glutaraldehyde treated chitin gave 1638 U/g-CI (chitin-isoamylase), 46% activity retention, and an optimal pH of 2.4. The kinetic data (K-m) indicated that CI (0.69 g/L) has similar mass transfer resistance to free enzyme (0.67 g/L), whereas CMCI (3.57 g/L) has much greater transport resistance.