Enhanced expression of endoinulinase from Aspergillus niger by codon optimization in Pichia pastoris and its application in inulooligosaccharide production.

In the present study, the endoinulinase gene (EnInu) from Aspergillus niger CICIM F0620 was optimized according to the codon usage of Pichia pastoris and both the native and the optimized gene were expressed in P. pastoris. Use of the optimized gene resulted in the secretion of recombinant endoinulinase activity that reached 1,349 U ml(-1), 4.18 times that observed using the native gene. This is the highest endoinulinase activity reported to date. The recombinant enzyme was optimally active at pH 6.0 and 60 °C. Moreover, inulooligosaccharides production from inulin was studied using the recombinant enzyme produced from the optimized gene. After 8 h under optimal conditions, which included 400 g l(-1) inulin, an enzyme concentration of 40 U g(-1) substrate, 50 °C and pH 6.0, the inulooligosaccharide yield was 91 %. The high substrate concentration and short reaction time described here should reduce production costs distinctly, compared with the conditions used in previous studies. Thus, this study may provide the basis for the industrial use of this recombinant endoinulinase for the production of inulooligosaccharides.