Simultaneous saccharification of inulin and ethanol fermentation by recombinant saccharomyces cerevisiae secreting inulinase

Various Saccharomyces cerevisiae strains were transformed with a 2μ-based multicopy expression plasmid, pYIGP, carrying Kluyveromyces marxianus inulinase gene under the control of GAPDH promoter. Among them two strains, SEY2102 and 2805, showed high levels of cell growth and inulinase expression, and were selected to study their fermentation properties on inulin. Jerusalem artichoke inulin was more effective for cell growth (10-11 g-dry wt./L at 48 hr) and inulinase expression (1.0 units/mL with SEY2102/pYIGP and 2.5 units/mL with 2805/pYIGP) than other inulin sources such as dahlia and chicory. It was also found that maximal ethanol production of 9 g/L was obtained from Jerusalem artichoke inulin at the early stationary phase (around 30 hr), indicating that recombinant S. cerevisiae cells secreting exoinulinase could be used for the simultaneous saccharification of inulin and ethanol fermentation.ope