The present invention relates to eukaryotic cells which have the ability to isomerize xylose directly into xylulose. The cells have acquired this ability by transformation with nucleotide sequences coding for a xylose isomerase that has one or more specific sequence elements typical for isomerases having the ability of functional expression in yeasts, such as e.g. xylose isomerases obtainable from a bacterium of the genera Clostridium and Fusobacterium or a tunicate form the genus Ciona. The cell preferably is a yeast or a filamentous fungus, more preferably a yeast is capable of anaerobic alcoholic fermentation.