Properties of Extremely Halotolerant Xylanase ScXyn22 from Schizophyllum commune and Its Effect on the Quality of Whole Wheat Bread

The GH11 endo-xylanase ScXyn22 from Schizophyllum commune was expressed in Pichia pastoris. Then, its enzymatic properties and its effect on the baking quality of whole wheat bread were characterized. The optimal pH and temperature for the purified recombinant enzyme were 4.5 and 55 ℃, respectively. Under these conditions, the specific activity, K_m and V_max of ScXyn22 were (5964.1 ± 429.4) U/mg, (3.25 ± 0.27) mg/mL and (1288 ± 9.14) μmol/(min mg), respectively. In the reaction system containing 1-5 mol/L NaCl, the activity of ScXyn22 toward birch xylan was significantly enhanced by 1.64, 2.13, 2.31, 2.39 and 2.3 folds, respectively. The activity of ScXyn22 toward wheat arabinoxylan was enhanced by 1.21, 1.46, 1.58, 1.48 and 1.16 folds, respectively. However, the activity of ScXyn22 toward oat β-glucan decreased by 19.31%, 47.72%, 55.97%, 45.99% and 38.18%, respectively, compared with that in the absence of NaCl. In simulated intestinal fluid, the remaining enzyme activity was 81% after 20 min and 65.77% after 120 min. Addition of xylanase had a significant effect on the quality of whole wheat bread. Addition of xylanase at 300 U/kg increased the specific volume of whole wheat bread by 19.7%, and at 150 U/kg decreased its firmness by 57.3%. These results showed that the xylanase has good application potential in whole wheat bread production.