Statistical optimization of tannase production from Penicillium variable using fruits (chebulic myrobalan) of Terminalia chebula

Statistically based experimental designs were applied to the optimization of cultural conditions for tannase production, an enzyme of great importance, from Penicillium variable. First, D-optimal design was used to evaluate the effects of variables, including concentrations of substrate (chebulic myrobalan, fruits of the tree Terminalia chebula), pH, inoculum density, agitation and incubation period, on tannase production. The optimum value of pH and inoculum density thus obtained was 5.0 and 5*10^(7) spores/50 ml respectively. Among these variables, substrate concentration, agitation and incubation period were identified to have the significant effects. Subsequently, the concentrations of substrate, agitation and incubation period were optimized using central composite design. The optimum values of the parameters thus obtained from the response surface methodology were 5.8 g of the substrate/50 ml of the medium, pH 5.0, 5*10^(7) spores/50 ml of inoculum density, 150 rev./min agitation rate and 72 h of incubation period. The subsequent verification experiments confirmed the validity of the models. This optimization strategy led to a 2.4-fold increase in the enzyme production from 13.6 units/ml obtained in D-optimal design to 33 units/ml in central composite design.