Preparation method of high-temperature xylanase

The invention relates to the field of biotechnology. A preparation method of high-temperature xylanase comprises the following steps: (1) preparation of crude enzyme: inoculating Thermobifida halotolerans YIM 90462 into liquid seed culture medium with inoculum size by 5 to 10 percent of volume, shaking culturing, transferring the Thermobifida halotolerans YIM 90462 into liquid fermentation medium by 5 to 10 percent of volume and obtaining crude enzyme; (2) concentrating the volume of the crude enzyme to 1/6 of original volume thereof by an ultra-filtration membrane package with molecular weight cut-off of 10 KDa; (3) adding ammonium sulfate into the concentrated enzyme to lead the saturation thereof to be 50 percent, obtaining precipitates by centrifugation and dissolving the precipitates in buffer solution; (4) taking supernatant fluid from the obtained liquid by centrifugation, adding the supernatant fluid into a Butyl-Sepharose chromatography column which is balanced by Tris-HCl buffer solution containing 0.3M of ammonium sulfate and having pH of 8.0; (5) taking supernatant fluid from the obtained liquid by centrifugation, adding the supernatant fluid into a Phenyl-Sepharose chromatography column which is balanced by Tris-HCl buffer solution containing 0.3M of ammonium sulfate and having pH of 8.0 and eluting the supernatant fluid with Tris-HCl buffer solution which does not contain ammonium sulfate and has pH of 8.0; (6) adding the supernatant fluid into Q-Sepharose chromatography column which is balanced by Tris-HCl buffer solution having pH of 8.0, collecting eluting peaks successively according to retention time, and remaining active components of the xylanase; and finally obtaining the xylanase with the activation of 573U/ml and purification yield of 9 percent.