| abstract |
The present invention relates to eukaryotic cells which have the ability to isomerise 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 froma bacterium of the genera Clostridiumand Fusobacteriumor a tunicate form the genus Ciona.The cell preferablyis ayeast or a filamentous fungus, more preferably a yeast is capable of anaerobic alcoholic fermentation. The may further comprise one or more genetic modifications that increase the flux of the pentose phosphate pathway, reduce unspecific aldose reductase activity, confer to the cell the ability to increase the specific xylulose kinase activity, convert L-arabinose into D-xylulose 5-phosphate, increase transport of at least one of xylose and arabinose into the host cell, decrease sensitivity to catabolite repression, increase tolerance to ethanol, osmolarity or organic acids; and/or reduce production of by-products. The cell preferably is a cell that has the ability to produce a fermentation product such as ethanol, lactic acid, 3-hydroxy-propionic acid,acrylic acid, acetic acid, succinic acid, citric acid, amino acids, 1,3-propane-diol, ethylene, glycerol, .beta.--lactam antibiotics and cephalosporins. The invention further relates to processes for producing these fermentation products wherein a cell of the invention is used to ferment xylose into the fermentation products. |