Optimisation of immobilisation conditions of β-galactosidase onto chitosan beads using response surface methodology

Abstract

Response Surface Methodology (RSM) was advantageously used to optimize production conditions of immobilization of β-galactosidase onto chitosan beads. The influence of immobilization conditions on the immobilized enzyme activity was studied by using Box-Behnken experimental design, resulting in the appropriate average values of OD420 and the maximum value of immobilized enzyme activity. This illustrated that the experimental model was reliable and the experimental results were of good stability. Analysis of variance was performed to determine the adequacy and significance of the quadratic model. Various model parameters also could be seen from F value that the interaction between three factors was not particularly obvious, but effects of X1, X12, X22 and X32 on the activity of immobilized enzyme were very obvious. The optimisation parameters studied in accordance with the results were: the appropriate average values of OD420 loaded in the range from 0.713 to 0.721. Furthermore the immobilized enzyme activity reached about 162U/g when the adsorption time, adsorption pH and cross-linking pH were 4h, 7 and 7, respectively. Thus, the relative activity of β-galactosidase immobilized increased more than 37% compared with the previous single factor research.