Study on the construction and expression of the engineered strain of Pichia pastoris for xylanase production
A gene encoding xylanase Xyn43A from Aspergillus niger XZ-3S was cloned into the Pichia pastoris expression vector,pPIC9K.The recombinant plasmid was linearized with Sal Ⅰ and then transformed into Pichia pastoris GS115 and KM71 by electroporation,respectively.After screening by MD medium,G418 concentration plate and shake bottle selection,two recombinant strains GS115/Xyn43A and KM71/Xyn43A were obtained.The best optimization schemes were obtained by single factor experiment and L9 (34) experiment.The optimal expression conditions of GS115/Xyn43A were methanol concentration of 2.0％,inoculation time of 24 h,induction time of 108 h,induction temperature of 30 ℃,and initial pH6.3.The optimal expression conditions of KM71/Xyn43A were methanol concentration of 1.75％,inoculation time of of 26 h,induction time of 132 h,induction temperature of 30 ℃,and initial pH6.5.Under the optimum conditions,the xylanase activity of the two recombinant strains were 139.36 U/mg and 143.29 U/mg,respectively.
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