Statistics based experimental designs were used to optimize the medium components and environmental factors for chitinase production. Considering the industrial importance of enzymes active at extremes of pH, the optimization studies were performed on strains of Streptomyces sp. NK1057, NK528 and NK951 which produce chitinases active at acidic and alkaline pH. Preliminary studies on the factors enabled identification of eight variables important with respect to chitinase production. The most important factors with respect to each strain were then identified using the 2-level fractional factorial. In general, chitin, yeast extract, ammonium sulphate, trace elements, pH and temperature affected chitinase production. CCD was used for model building and chitin and yeast extract were found to have an interactive effect on chitinase production in Streptomyces sp. NK1057 whereas yeast extract alone had a quadratic effect on chitinase production in all the three strains. Similarly, ammonium sulphate and pH had a quadratic effect on chitinase production in Streptomyces sp. NK528 and NK951. The optimal values of important variables were determined by response surface methodology (RSM) and numerical optimization. The verification confirmed the validity of the models built. This optimization strategy led to an increase in chitinase production in the strains Streptomyces sp. NK1057, NK528 and NK951 by 29, 9.3 and 28%, respectively. (C) 2004 Elsevier Ltd. All rights reserved.