Abstract:Both endoglucanase and xylanase are additives in feed for mono-gastric animal. Co-expression of endoglucanase and xylanase in P. pastoris is a useful way to reduce the production cost in feedstuff industry. An endoglucanase-encoding gene(Aucel12A) from Aspergillus usamii was expressed in P. pastoris,and the engineering strain with the highest endoglucanase activity was labeled GSC7. Then,a recombinant vector,pPICZαA-Aoxyn11A,was constructed and linearized by Sac I,followed by transforming it into GSC7. Ultimately,the endoglucanase and xylanase genes were successfully co-expressed in P. pastoris. One strain harbored genes Aoxyn11A and Aucel12A,with the highest xylanase and endoglucanase activities,was labeled GSCX8. The enzymatic properties of the recombinant AuCel12A and AoXyn11A,expressed in GSCX8,were characterized. Meanwhile,to analyze the genetic stability of GSCX8,the xylanase and endoglucanase activities of different strains after passing 10 generations were also measured. After strain GSCX8 was induced for 96 h,the activities of recombinant AuCel12A and AoXyn11A in the cultured supernatant were 47.77 IU/mL and 192.71 IU/mL,respectively,which were about 85% and 80% of that of enzymes expressed by the single gene engineering strains GSCZ and GSX5. The recombinant AuCel12A displayed the optimal activity at pH 4.0 and 50 ℃,and was stable over a pH range of 3.0~8.5 and at 60 ℃ or below. Besides,the recombinant AoXyn11A displayed the optimal activity at pH 5.5 and 55 ℃,and was stable over a pH range of 3.0~10.0 and at 50 ℃ or below. Additionally,the activities of the two enzymes were well maintained after the GSCX8 passing 10 generations.
