Chitosan and its amino acids condensation adducts as reactive natural polymer supports for cellulase immobilization

Cellulase [1,4-(1,3;1,4)-β-d-glucan 4-glucanohydrolase], was immobilized directly on chitosan, chitosan–l-glutamic acid and chitosan–4-amino butyric acid by covalent attachment and cross-linking methods. The properties of the immobilized cellulase were investigated and compared with those of the free one. For the assays carried out via cross-linking method at 25 °C and pH 7, the retained activities were found to be 65.52%, 85.32% and 63.19% for chitosan, chitosan–l-glutamic acid and chitosan–4-aminobutyric acid cross-linked with 1% of glutaricdialdehyde (GDA), respectively. The immobilized cellulase had better stability and higher retained activities with respect to pH, temperature and storage stability than the free one. In the repeated use experiments, the immobilized cellulase using chitosan–GDA (1%) retained about 60% from its original activity after 6 times. In contrast, the activities of immobilized cellulase on chitosan–l-glutamic acid–GDA (1%) and chitosan–4-aminobutyric acid–GDA (1%) did not change after 10 and 7 times respectively. The retained activities after 25 times reusability were 70% and 50% from their original activity for the aforementioned carriers respectively.