Abstract: Expansin can weaken the hydrogen bond between cell wall polysaccharides and enhance the efficiency of polysaccharide degradation by polysaccharide degrading enzyme. It has a wide range of application value in the field of food, bioenergy and biopharmaceutical.In the natural state, the expression of expansin protein in plants, fungi, bacteria and other organisms is less. At present, the research on the recombinant expression of expansin in Bacillus subtilis has been widely concerned. In this project, the expression project strain (newexpansin/ pelA-pET-28a(+) / BL21(DE3)) was constructed with the pectate lyase A (pelA gene from Aspergillus nidulans) as the fusion tag. At OD600 =0. 4, 0. 01 mmol/ L IPTG, 15 ℃ and 150 r/ min for 24 h, the fusion protein production was about 3. 0 mg/ mL. A one-step his-tag affinity purification process was established for the fusion protein and the concentration of imidazole in the sample loading, cleaning and elution buffer were 30, 60 and 500 mmol/ L, the purity of the target protein was about 95%, and the yield was about 75%. The degradation efficiencies of the fusion protein with cellulase, pectinase and xylanase were 300%,150% and 125%, respectively. This project laid the foundation for the application of expansin in the fields of food, energy, medicine and agriculture.

Key words: expansin, pectate lyase A, fusion expression, isolation and purification, activity analysis