Abstract:Xylanase plays a key role in the degradation of xylan.Acid xylanase has great application potential in food processing，wine making，juice clarification，and other industrial applications.In this study，the acid xylanase gene，XynA，was heterologously expressed in Escherichia coli by molecular cloning technology to study its enzymatic properties.Moreover，the optimal immobilized enzyme conditions were obtained using a response surface optimization test.The XynA gene was successfully recombined into Escherichia coli BL21（DE3）to study its enzymatic properties.Xylanase was found to have good acid resistance，as its optimal pH value was 5.0，and it remained stable when the pH value increased was from 4.5 to 5.5.The relative enzyme activity was more than 62.37%.The optimum temperature was 55 ℃，and the enzyme was stable at 35 to 45 ℃.Response surface analysis was used to optimize the immobilization conditions of xylanase.When the concentration of chitosan was 2.0%，the cross-linking time was 3 h，the immobilization time was 12 h，and the active recovery of xylanase was 39.45%.