TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preparation: (I) may be prepared by standard recombinant methodologiesPreferred Sequence: (I) has preferably 90% or more homology with S1. (I) presents an optimum enzymatic activity at a pH between 4.5-7.0, at a temperature between 35-55degreesC. (I) is extra-cellularly or intra-cellularly expressed by (V). (II) has preferably 90% or more homology with S3. (II) comprising S3 or its portion, encodes a polypeptide having xylanolytic activity. (IV) is a plasmid incorporated in Escherichia coli and has the deposit number LMBP-39987.Preferred Host Cell: (V) is selected from bacteria or fungi, including yeast. EXAMPLE - A DNA fragment covering the coding region of xylanolytic enzyme and its terminator region was amplified by polymerase chain reaction (PCR). The first synthetic oligonucleotide GGAATTCCATAATGGTCTCTTTCT was chosen to contain the ATG codon corresponding to the first methionine of the coding region of the polypeptide gene and an EcoRI recognition site. The second oligonucleotide GCTCTAGAGCCACTTGTGACATGCT corresponded to the sequence located 250 bp downstream of the last codon and contained a XbaI restriction site. Both primers (40 pmoles) were used for a PCR reaction with approximately 40 ng of pPGXYNA plasmid DNA as template. The amplified DNA fragment was purified and recovered in a final volume of 50 microl. The extremities of the fragment were removed by EcoRI-XbaI digestion. The fragment was then purified after separation by electrophoresis and recovered in 30 microl water. The PCR DNA fragment was inserted between EcoRI-XbaI restriction sites of the pBluescript II SK (+) vector. The new plasmid was termed pPGXYN1E-X. The primer of glyceraldehyde-3-P dehydrogenase gene from Aspergillus nidulans was cloned in front of the xylanolytic enzyme gene. The promoter was inserted into the pBluescript II SK(+) plasmid between two EcoRI restriction sites to give the pSK-GPDp plasmid using standard procedures. pSK-GPDp and pPGXYN1E-X plasmids were digested by EcoRI restriction enzyme. The DNA fragments of interest were then separated by electrophoresis and purified. The purified promoter DNA fragment was inserted by ligation between EcoRI sites of pPGXYN1E-X, and the ligation mixture was electroporated into competent Escherichia coli DH10b cells. A right clone was selected after analysis of transformants plasmids using standard procedures. The new plasmid was termed pGPDp-PGXYN1, which was cotransformed into A.oryzae MUCL 14492, with the p3SR2 plasmid that contains a selection marker for recovering transformants. 48 transformants were analyzed for the xylanolytic enzyme expression. They were grown in Aspergillus Minimum Liquid Medium supplemented with 3% sucrose as carbon source and 0.5% Bacto yeast extract. After 75 hours at 30degreesC, the supernatant of the cultures was assayed for xylanolytic activity. 10 of the transformants showed a significantly higher xylanolytic activity as compared to a control strain transformed only with the p3SR2 plasmid.