To validate the optimum combination of the process variables, confirmatory experiments were carried out by selecting the best combination of the four variables from the contour plot (Fig. 1). At hold values of substrate concentration of 5 g, initial pH of 5, inoculation with 1 105 spores and moisture ratio of 1: 6.79 (w/v), cellulolytic activity of 10.96 U/g (0.98 U/ml) was obtained. The filter paper activity obtained under optimized parameters was