Enhanced production of Aspergillus ficuum endoinulinase in Saccharomyces cerevisiae by using the SUC2-deletion mutation

The inuB gene, encoding an Aspergillus ficuum endoinulinase, was expressed by the Kluyveromyces marxianus INU1 promoter in Saccharomyces cerevisiae to produce an enzyme free of an exoinulinase and an extracellular invertase. The recombinant yeast strain produced the enzyme at the concentration of 83.0 U/ml with 2% glucose as a carbon source and 2% fructose as an inducer added after 12 h of initiation of culture. Two Δ suc2 mutants produced higher amounts of the enzyme by 13–49 U/ml than SUC2 wild types. The molecular weight of the secreted enzyme was 67 kDa as measured by SDS-PAGE and Western blot analysis, which was larger by 1–3 kDa than those of the purified enzymes. The purified enzyme has been reported to be a mixture of two polypeptides of 64 kDa and 66 kDa in molecular weight.