alpha-Amylase from Bacillus subtilis was immobilized on insoluble chitosan and its amino acid (L-glutamic acid and 4-aminobutyric acid) condensation adducts with the direct covalent attachment method and With glutaric dialdehyde (GDA) as a crosslinking agent. The immobilization process was carried Out at 25 degrees C and pH 6.9, and the maximum retained activity was obtained with 3 mg of alpha-amylase. The properties of the immobilized alpha-amylase were investigated and compared with those of the free alpha-amylase. For the assays carried out via the crosslinking method at 25 degrees C and pH 6.9, the retained activities were found to be 68.59, 97.36, and 79.50% for chitosan, chitosan-L-glutamic acid, and chitosan-4-aminobutyric acid crosslinked with 1% GDA, respectively. The immobilized alpha-amylase had better stability and higher retained activities with respect to the pH, temperature, and storage stability than the free alpha-amylase. In the repeated-use experiments, the alpha-amylase immobilized with chitosan-GDA (1%) retained about 46.45% of its original activity after 25 uses. In contrast, the activities of alpha-amylase immobilized on chitosan-L-glutamic acid-GDA (1%) and chitosan-4-aminobutyric acid-GDA (1%) did not change after 11 and 8 uses, respectively. The retained activities after 25 uses were 79 and 71%, with respect to the original activity for the aforementioned carriers. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 805-814, 2009