An integrated classical and statistical optimization approach involving the combination of Placket–Burman design (PBD) and Central Composite Design (CCD) was employed for increasing phytase yield. PBD was used to evaluate the effect of 9 variables related to phytase production from probiotic strain B. subtilis, and three statistically significant variables, namely, glucose, beef extract and potassium phosphate were selected for further optimization studies. The levels of five variables for maximum phytase production were determined by a CCD. The optimum values for the factors were determined via response surface methodology (RSM) as: 6.59 gl-1 of glucose, 6 gl-1 of beef extract and 2.75 gl-1 of potassium phosphate respectively. Phytase production improved from 2.74 EUml-1 to 46.76 EUml-1 indicating 17-fold increase in activity after optimization.
