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%.