Immobilization of Bacillus licheniformis l-arabinose isomerase (BLAI) on aminopropyl glass modified with glutaraldehyde (4 mg protein g support(-1)) was found to enhance the enzyme activity. The immobilization yield of BLAI was proportional to the quantity of amino groups on the surface of support. Reducing particle size increased the adsorption capacity (q (m)) and affinity (k (a)). The pH and temperature for immobilization were optimized to be pH 7.1 and 33A degrees C using response surface methodology (RSM). The immobilized enzyme was characterized and compared to the free enzyme. There is no change in optimal pH and temperature before and after immobilization. However, the immobilized BLAI enzyme achieved 145% of the activity of the free enzyme. Correspondingly, the catalytic efficiency (k (cat)/K (m)) was improved 1.47-fold after immobilization compared to the free enzyme. The thermal stability was improved 138-fold (t (1/2) increased from 2 to 275 h) at 50A degrees C following immobilization.