Identification and Optimization of Critical Medium Components Using Statistical Experimental Designs for Enhanced Production of Xylanase from Aspergillus flavus DFR-6

The Plackett-Burman screening design (PBSD) and Central composite rotatable design (CCRD) were used to optimize the fermentation parameters for enhanced xylanase production from Aspergillus flavus DFR-6 in submerged cultivation. The PBSD demonstrated that the positive main effects of yeast extract, wheat bran, Tween 80 and NaNO3 were significant at 10 % level of significance. The interactive effects of these factors were deduced using CCRD and finally, the production medium was optimized using Design-Expert software. The optimized medium conditions with 97.2 % desirability and with respect to `minimum organic nitrogen source’ were (in g/L): NaNO3 4.09, K2HPO4 0.5, MgSO4·7H2O 0.25, KCl 0.25, FeSO4 0.005, wheat bran 24.99, yeast extract 10 and Tween 80 0.21 mL/L, pH=5.0. The enzyme was produced in 50 mL of medium working volume using 500-mL conical flask at 35 °C with 1 % (by volume) of inoculum size. The production titre of xylanase under aforementioned conditions was 31.4 U/mL after 6 days of static fermentation which is approx. fourfold higher than obtained from the unoptimized medium.