毛壳霉木聚糖酶B（CsXyn11B）的分泌表达及其在面包中的应用

目的:对毛壳霉（Chaetomium sp.）CQ31木聚糖酶B（CsXyn11B）进行分泌表达，以提高产酶水平并探究在面包烘焙中的应用价值。方法:将木聚糖酶基因在毕赤酵母中表达，高密度发酵提高其产酶水平，对酶学性质进行表征并将其应用在面包烘焙中。结果:重组菌经高密度发酵156 h，木聚糖酶酶活力为2788 U/mL。CsXyn11B最适pH为8.0，最适温度为65 ℃。CsXyn11B能够水解多种木聚糖底物，对燕麦木聚糖、小麦阿拉伯木聚糖、榉木木聚糖和桦木木聚糖的比酶活分别为1145.8、1041.7、692.3和653.3 U/mg。该酶水解阿拉伯木聚糖，水解产物以聚合度4~6的低聚木糖为主。在面包制作过程中加入3 mg/kg CsXyn11B使面包比容增加15.9%，面包硬度降低25.3%，4 ℃贮藏2 d后硬度比对照组降低17%。结论:毛壳霉木聚糖酶B的优良酶学特性使其在烘焙食品中具有良好的应用前景。

Secretion Expression of Xylanase B (CsXyn11B) from Chaetomium sp. and Its Application in Bread

Objective: A xylanase B (CsXyn11B) gene from Chaetomium sp. CQ31 was extracellularly expressed to improve the enzyme production and explore its application in bread baking. Methods: The xylanase (CsXyn11B) gene was expressed in Pichia pastoris, and the enzyme production was improved by high-density fermentation. The enzymae was characterized and applied in bread baking. Results: The recombinant strain was fermented at high density for 156 h, and the enzyme activity of xylanase was 2788 U/mL. The optimal pH of CsXyn11B was pH8.0, and the optimal temperature was 65 ℃. CsXyn11B hydrolyzed a variety of xylans, and the specific enzymatic activities of oat xylan, wheat arabinoxylan, beech xylan and birch xylan were 1145.8, 1041.7, 692.3 and 653.3 U/mg, respectively. The enzyme hydrolyzed arabinoxylan, and the hydrolyzed product were mainly xylo-oligosaccharides with a degree of polymerization of 4~6. Addition of CsXyn11B (3 mg/kg) into the bread making remarkably improved the specific volume by 15.9% and decreased the hardness by 25.3%. Compared with the control group, the hardness decreased by 17% after storage at 4 ℃ for 2 d. Conclusion: The excellent properties of xylanase B from Chaetomium sp. made it have a promising application prospect in baked food.