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New xylanases to obtain modified eucalypt fibres with high-cellulose content

Valls, Cristina, Gallardo, Oscar, Vidal, Teresa, Pastor, Francisco Ignacio Javier, Díaz, Pilar, Roncero, M. Blanca
Bioresource technology 2010 v.101 no.19 pp. 7439-7445
Eucalyptus, absorbance, acids, chemical oxygen demand, chlorine, color, delignification, effluents, paper, paper pulp, xylanases, xylooligosaccharides
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.