Nutritional requirement for maximum production of chitin deacetylase (CDA), an enzyme used for bioconversion of chitin to chitosan, under submerged condition by mutant Penicillium oxalicum SAE(M)-51 was optimized using response surface methodology (RSM). Among the eight nutritional elements studied, yeast-extract, peptone, (NH4)(2)SO4 and MgSO4 were identified as the most critical variables for CDA production by Plackett-Burman design first. Further optimization of these variables was done by using a four factor central composite design (CCD). The model came out to be significant and statistical analysis (analysis of variance, ANOVA) of the results showed that yeast extract had contributed significantly (quadratic effect) to the response and its interaction with magnesium sulfate was strong. Peptone was also found to be another important component in the medium that influence the CDA production. Optimum concentration of the variables for enhanced CDA production determined by CCD were-yeast extract (X-1) 3.165 gl(-1), peptone (X-2) 4.754 gl(-1), (NH4)(2)SO4 (X-4) 0.255 gl(-1) and MgSO4 (X-5) 0.535 gl(-1). 2.0 fold enhancement in CDA titres was attained in shake flasks, when the variables were used at their optimum levels. CDA production (414.7 +/- 6.32 Ul(-1)) in the optimized medium was in good agreement with the values predicted by the quadratic model (399.08 Ul(-1)), confirming the validity of the model. Employment of optimal growth medium would result into large scale production of microbial deacetylase, which further heighten its potential for biological production of chitosan. (C) 2011 Published by Elsevier Ltd.