Optimization of biocatalytic synthesis of Chitosan Ester using response surface methodology

Esterification of chitosan with adipic acid catalyzed by immobilized Candida antarctica lipase B was carried out in this study. Response surface methodology (RSM) based on a four-factor- five-level small central composite design (SCCD) was employed to model and analyze the reaction. A total of 21 experiments representing different combinations of the four reaction parameters including chitosan concentration (0.01-0.10 g/mL), temperature (35-65◦C), time (15-240 min), and enzyme amount (5-20 % w/w of total substrate) were generated. A partial cubic equation was fitted to the data with a R2 of 0.9738 showing a high correlation between predicted and experimental values. The enzyme was capable of esterifying chitosan with a maximum yield of 45.3%. Chitosan concentration was found to be the most significant parameter which influenced the ester synthesis. At the optimal conditions of a short reaction time 15 min, 65oC, 0.10 g/mL of chitosan and 18.7% of enzyme, the esterification percentage was 43.5%.