裂褶菌极端嗜盐木聚糖酶ScXyn22的性质及对全麦面包品质的影响

研究裂褶菌（Schizophyllum commune）来源GH11家族木聚糖酶ScXyn22在毕赤酵母的表达，分析该酶的酶学性质及其对全麦面包品质的影响。ScXyn22的最适pH值和温度为4.5和55 ℃，为内切型木聚糖酶。ScXyn22水解桦木木聚糖比活力为（5 964.1±429.4）U/mg，Km为（3.25±0.27）mg/mL，Vmax为（1 288±9.14）μmol/（min·mg）。ScXyn22在含有1～5 mol/L NaCl反应体系中，水解桦木木聚糖的酶活力分别提高到1.64、2.13、2.31、2.39、2.3 倍；水解小麦阿拉伯木聚糖酶活力提高到1.21、1.46、1.58、1.48、1.16 倍；但对β-燕麦葡聚糖的水解活性降低19.31%、47.72%、55.97%、45.99%、38.18%。模拟人工肠液环境下，ScXyn22在20 min内的剩余酶活力为81%，在120 min后剩余酶活力65.77%。添加木聚糖酶对全麦面包的品质影响显著，当ScXyn22添加量为300 U/kg时全麦面包比容提高了19.7%；当添加量为150 U/kg时，面包硬度降低57.3%。该结果显示该木聚糖酶在全麦面包生产中具有很好的应用潜力。

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, Km and Vmax of ScXyn22 were (5 964.1 ± 429.4) U/mg, (3.25 ± 0.27) mg/mL and (1 288 ± 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.