Expression of Acid Xylanase in Escherichia coli Induced by Lactose

[Objective]Cells of E.coli BL21 bearing the acid xylanase from Aspergillus usamii under the control of the lacDE3 promoter were induced with lactose.[Method] With the specific activity of recombinant xylanase as the evaluation index,the effects of culture conditions such as concentration of the inducer,the time of culture before induction,the time and the temperature of induction culture on the expression of the recombinant protein of E.coli BL21(DE3) were investigated by using single factor experiment and L9(34) orthogonal experiment.[Result]The influencing degree of each factor was as follows: induction time the temperature of induction culture culture time inducer concentration.The optimum combination was obtained as: inducer concentration of 5 g/L,induction time of 0.5 h,culture time of 4.5 h and induction temperature of 32 ℃.Under these conditions.the specific activity of recombinant xylanase reached 49.69 U/mg.[Conclusion] Lactose could be used as an inducer in the expression of xylanase in E.coli.