Optimization of Fermentation Conditions for β-1,4-xylanase Production by Aspergillus flavus and Its Enzymatic Properties

This study was aimed at optimization of the fermentation conditions for β-1,4-xylanase production by Aspergillus flavus and characterization of its enzymatic properties. The fermentation conditions in shake flask were optimized by a single-factor experiment. And the enzymatic properties of the enzyme were analyzed by SDS-PAGE,zymogram and TLC. The results indicated that the optimal culture medium components for β-1,4-xylanase production were 3.5% wheat bran,3.0%(NH₄)₂HPO₄,1.0% Tween-60,0.5% NaCl,0.05% MgSO₄·7H₂O and 0.075% KH₂PO₄.The highest enzyme activity of 115.08 U/mL was obtained when the strain was cultured at 35 ℃ for 5 d in the optimized culture medium,which was 9.4 times compared with the initial activity. Two β-1,4-xylanases were secreted by A. flavus,and their molecular mass were different from all previous studies. The crude enzyme’s optimal temperature and pH were determined to be 55 ℃ and 7.5,respectively. It was stable at 30~50 ℃and within pH5.5~9.0. The enzyme could not only efficiently hydrolyze beechwood xylan to produce xylooligosaccharides,but also weakly degrade the barley glucan,suggesting it was a good candidate for lignocelluloses’ degradation.