Jerusalem artichoke mashed tubers were fermented using single yeasts and a bacterium as well as mixed culture of microorganisms. Kluyveromyces fragilis, a yeast with an active inulinase, was used together with either a commercial distillery yeast, Saccharomyces cerevisiae, or the bacterium Zymomonas mobilis. After batch fermentation the best ethanol concentration of 0.48 g g(-1) for the mixed population and 0.46 g g(-1) for the single population can be obtained. The theoretical yield of the mixed cultures was 2-12% higher than for the single microorganism.