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

Ajay Pal* and Farhath Khanum

Biochemistry and Nutrition Discipline, Defence Food Research Laboratory, Siddarthanagar, Mysore 570 011, India

Article history:
Received December 16, 2009
Accepted July 15, 2010

Key words:
statistical design, optimization, xylanase, submerged fermentation, lignocellulose

Summary:                                                                                                                                                                                             
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.

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