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Xylanase is a novel and safe flour additive that effectively enhances dough properties and baking quality. To explore new sources of xylanase and evaluate its application in bread baking, xylanase from Caldicellulosiruptor owensensis was heterogeneously expressed in Escherichia coli by fusion with Sumo tag. The enzymatic properties of the xylanase SumoXyn and its impact on bread quality were investigated. The xylanase from Caldicellulosiruptor owensensis was efficiently expressed in E.coli and the enzyme was obtained with high purity by simply heating the cell lysate at 75 °C for 30 minutes. Nano DSF analysis showed that the Tm value of this enzyme was 83.5 °C. The optimum pH of the enzyme was 9.0, but it still had more than 60% activity at pH 5-10. Treated in pH 4-10 buffer for 24 h, SumoXyn still had more than 80% residual activity. SumoXyn displayed the highest activity at 80 °C, but it still has 50% of the highest activity at 100 °C, and the residual activity was about 75% after heating at 75 °C for 1 h, indicating that Sumoxyn had good pH stability and thermal stability. Using bagasse xylan as substrate, the Vmax was 2 354.52 μmol/(min·mg), the Kmwas 2.26 mg/mL and the Kcat was 214.68 S-1. Using 200 g high gluten whole wheat flour to make bread, the effects of SumoXyn supplemented with 3 mg, 6 mg, 9 mg, respectively, on the quality of whole wheat bread were investigated. It was found that with the increase of SumoXyn supplemented, the specific volume and elasticity of bread increased, the hardness and chewability decreased, and the quality of whole wheat bread was significantly improved. These findings suggest that SumoXyn has great potential as a flour improver. [ABSTRACT FROM AUTHOR]