Characterization of Bacillus kaustophilus leucine aminopeptidase immobilized in Ca-alginate/k-carrageenan beads

Properties of Bacillus kaustophilus leucine aminopeptidase (BkLAP) immobilized by entrapment in Ca-alginate/k-carrageenan hydrogel were examined. For the free and immobilized BkLAP, optimum pH was found to be 8.0 and 7.5, respectively. The optimum temperature of the free and immobilized enzymes was also observed to be 55 and 60 degrees C, respectively. Thermal stability of BkLAP was increased as a result of immobilization. Maximum reaction rate (V-max) and Michalis-Menten constant (K-m) of BkLAP were changed significantly upon immobilization. The immobilized enzyme could be reused at least up to 10 cycles without any further loss of activity. After incubating at 4 degrees C for 30 days, the stability values for the immobilized enzyme system were found to be 90%. In the presence of 50 mM H2O2, the immobilized BkLAP was more stable respective to the free enzyme, indicating that the oxidative stability of the enzyme can be improved by immobilization. (c) 2007 Elsevier B.V. All rights reserved.