Overexpression of the endo-inulinase gene from Aspergillus niger in Pichia pastoris and its application research

The endo- inulinase gene( 1551 bp) was amplified from the total DNA of A. niger by PCR and subsequently cloned into p PIC9 K. The recombinant plasmid was linearized by Sac I and transformed into P.pastoris GS115 by electroporation,yielding the recombinant strain P. pastoris GS115/p PIC9K-endo I. Then right transformants were isolated and the recombinant enzyme derived from fermentation was characterized.Its optimal p H and optimum temperature of the recombinant enzyme was 5 and 60 ℃,respectively,moreover83.2% of the original enzymatic activity remained after the incubation of recombinant enzyme at 55 ℃ for 9hours. It was shown that Cu²⁺,Ag⁺ strongly inhibited the recombinant enzyme activity. The hydrolytic process analyses showed that the recombinant endo- inulinase could hydrolyze 4 %( w / v) inulin into DP3- 6 of fructooligosaccharides in 8 h. The conversion rate reached 63.5% in 11 h. The research laid a foundation for the produce of fructooligosaccharides.