Statistical optimization of chitosanase production by Aspergillus sp QD-2 in submerged fermentation

Cultivation of chitosanase production by Aspergillus sp. QD-2 under submerged fermentation was optimized. Factors including (NH4)(2)SO4, inoculum size and initial pH were identified by two-level Plackett-Burman design (PBD) as significant for chitosanase production. The path of steepest ascent was undertaken to determine the optimal region of three significant factors. To determine the optimal values of the significant variables, Box-Behnken design (BBD) and response surface analysis were employed. The quadratic regression model of producing chitosanase showed that the optimal cultivation conditions ((NH4)(2)SO4 5.164 g/l, inoculum size 8.204% (v/v) and initial pH 4.074) resulted in the improvement of chitosanase activity (85.816 U/ml) as compared to the initial level (26.515 U/ml) after 72 h of fermentation. The optimal pH and temperature of the crude chitosanase were determined to be 5.6 and 55 degrees C, respectively.