Optimum pH of six kinds of xylanase (GH11). The optimal pH of each xylanase was determined using the DNS method with 1% (w/v) birch-wood xylan. The buffers were: 0.1 M citric acid buffer pH 3.0 – 3.5; 0.1 M sodium acetate pH 4.0 − 4.5; 0.1 M sodium citrate pH 5.0 – 6.0; 0.1 M Hepes-NaOH pH 7.0; 0.1 M Tris–HCl pH 8.0. The enzymes are: XylA (black diamond), XylB (black square), XylC (black triangle), XylE (white circle), XylF (black dash) and XylG (black circle). The percent relative activity is based on the activity of XylC at pH 4.0. The data plotted are averages of triplicate experiments.