A Peptidase Enzyme from Bacillus cereus with Antimicrobial Properties: Optimizing the Immobilization in Chitosan Beads Using Box-Behnken Design

Abstract

Enzymes are exploited as catalysts in many industrial, biomedical, and analytical processes. There has been considerable interest in the development of carrier systems for enzyme immobilization because immobilized enzymes have enhanced stability compared to soluble enzymes, and can easily be separated from the reaction. In the current study, microbial peptidases liberated by B. cereus were immobilized in cross-linked chitosan beads and characterized using azocasein as a substrate. The Box-Behnken design was applied to determine the optimal conditions to maximize proteolytic activity. An empirical second-order model was determined by multiple regression analysis of the experimental data to describe the relationship between tested variables and the response. The determination coefficients (R2) were above 90%. Under optimal conditions (2.2 mm bead diameter, 1.06 enzyme/ bead ratio, 5.82% v/v glutaraldehyde and 18°C) the proteolytic activity was 0.938 U/ml. The retained immobilized enzyme can be reused up to five times. The storage stability of immobilized peptidases at 4°C was up to 10 days, while at 32°C the enzyme lost its activity within three days. Finally, novel antimicrobial properties of the immobilized peptidases were found. These results could have important benefit for the food industry.