NOVELTY - A protein (P1) having ( greater than or equal to 70% identity, preferably greater than or equal to 80% identity, especially greater than or equal to 90% identity, particularly greater than or equal to 95% identity) to specific peptide sequence and having xylose-isomerase activity in a eukaryotic cell; is new.    USE - As protein having xylose-isomerase activity, and eukaryotic cell (preferably genetically modified yeast cell) expressing the protein having xylose-isomerase activity, which are useful for fermentation of biomass from xylose-carbon source containing media; as biocatalyst in situ or in purified form for production of isomerized sugar products or intermediates (preferably isomerized sugar products); for producing ethanol from xylose or glucose-xylose mixture; and for producing fermentation product selected from lactic acid, acetic acid, succinic acid, amino acids, 1,3-propane-diol, ethylene, glycerol, beta -lactam antibiotics, cephalosporins, biofuels, butanol, ethanol, lactic acid, and itaconic acid (preferably butanol, or ethanol, especially ethanol) (all claimed).    ADVANTAGE - The protein and DNA sequences of xylose isomerase genes can be functionally expressed in lower eukaryotic cells (especially yeasts), such that protein having xylose isomerase activity suitable for genetic construction of eukaryotic cells with enhanced xylose metabolism or consumption, which then results in improved biomass formation in presence of xylose and/or provides improved formation of metabolites; which is difficult to realize in satisfactory manner with means known to the art. Thus is suitable for forming industrial production strains, especially production strains of genus Saccharomyces. The eukaryotic cells (C1) and (C2) and the genetically modified yeast cells (C3) achieve increased rate of xylose consumption.    DETAILED DESCRIPTION - A protein (P1) having ( greater than or equal to 70% identity, preferably greater than or equal to 80% identity, especially greater than or equal to 90% identity, particularly greater than or equal to 95% identity) to defined peptide sequence containing 457 amino acids (SEQ ID NO. 2) as given in the specification and having xylose-isomerase activity in a eukaryotic cell; is new. INDEPENDENT CLAIMS are included for the following: (1) a DNA molecule (N1) encoding a protein of ( greater than or equal to 70% identity, preferably greater than or equal to 80% identity, especially greater than or equal to 90% identity, particularly greater than or equal to 95% identity) to the (SEQ ID NO. 2), where the protein has xylose-isomerase activity in the eukaryotic cell; (2) a eukaryotic cell (C1) comprising the DNA molecule (N1); (3) a eukaryotic cell (C2) expressing the protein (P1); (4) a genetically modified yeast cell (C3) comprising an exogenous xylose isomerase gene functional in the yeast cell, where preferably the exogenous xylose isomerase gene is operatively linked to promoter and terminator sequences that are functional in the yeast cell; (5) use of the DNA molecule (N1) for transformation of a eukaryotic cell; (6) process for producing ethanol from xylose or a glucose-xylose mixture involving: using a yeast (preferably Saccharomyces cerevisiae), which expresses the protein (P1); and (7) process for producing a fermentation product selected from lactic acid, acetic acid, succinic acid, amino acids, 1,3-propane-diol, ethylene, glycerol, beta -lactam antibiotics, cephalosporins, biofuels, butanol, ethanol, lactic acid, and itaconic acid (preferably butanol, or ethanol, especially ethanol) involving: (a) fermenting a medium containing a source of xylose with the cell (C1), (C2) or (C3), and optionally, (b) recovering the fermentation product.