TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Polypeptide: The polypeptide yields xylose and glucose in a weight ratio of at least 10:1 when subjecting wheat straw to the polypeptide at pH 5 and 45 degrees C. The polypeptide shows optimum xylanase activity in the pH range of 5-6. The polypeptide comprises an amino acid sequence having at least 70%, more preferably at least 75-95% sequence identity to the SEQ ID No: 1. The polypeptide comprises a defined sequence of 307, 330, 331, or 414 amino acids (SEQ ID No: 1-4), given in the specification, or a sequence as defined by SEQ ID No: 1-4 where 1 to 30 amino acid residues are substituted, deleted, or inserted. The polypeptide maintains at least 80%, preferably 90% of its xylanase activity after having been subjected to trypsin at pH 7.8 and 50 degrees C for 1 hour. The xylanase shows an optimum activity for the hydrolysis of xylose from wheat straw in the temperature of 45-80 degrees C, preferably 65-75 degrees C. The polypeptide is expressed and secreted at a level of more than 100 mg/l, more preferably of more than 1 g/l into the supernatant after introduction of a nucleic acid encoding a polypeptide having an amino acid sequence with at least 70% more preferably at least 75-95% sequence identity to the SEQ ID No: 1 into a yeast. Preferred Host Cell: The host cell is derived from Saccharomyces cerevisiae, Schizosaccharomyces pombe, Kluyveromyces lactis, Pichia pastoris, Pichia angusta, Hansenula polymorpha, Aspergillus niger, Trichoderma reesei, Penicillium sp.. The host cell is a methylotrophic yeast, preferably derived from host cells comprising Pichia methanolica, P. pastoris, P. angusta, and H. polymorpha. Preparation (claimed): Producing a xylanase protein comprises obtaining a host cell, which has been transformed with a vector comprising the nucleic acid of (1); cultivating the host cell under conditions under which the xylanase protein is expressed; and recovering the xylanase protein. The host cell is a yeast cell and the xylanase protein has a sequence as defined by SEQ ID No: 3, or a sequence as defined by SEQ ID No: 3 where 1 to 30 amino acid residues are substituted, deleted, or inserted, is expressed. SPECIFIC SEQUENCES - The xylanase protein comprises a defined sequence of 307, 330, 331, or 414 amino acids (SEQ ID No: 1-4), given in the specification.    EXAMPLE - No suitable example given.