Modified fibres with high-cellulose content were obtained with two new bacterial xylanases from families 11 and 5. These xylanases were applied separately or simultaneously in a complete ECF (Elemental Chlorine Free) bleaching sequence. Both xylanases improved delignification and bleaching during the sequence and a synergistic effect of the enzymes was observed on several pulp and paper properties. The xylanases boosted the release of xylooligosaccharides branched with hexenuronic acids (HexA), giving rise to fibres with a reduced HexA and xylose content. However, these effects depended on the xylanase used, being the family 11 enzyme more efficient than the family 5 xylanase. Effluent properties such as absorbance spectra UV/Vis, COD and colour were affected by the enzymatic sequences as a consequence of the dissolution of lignin and xylooligosaccharides. Some changes in the fibre morphology were also produced without affecting the final paper strength properties. (C) 2010 Elsevier Ltd. All rights reserved.