Effect of a novel enzyme on fibre morphology during ECF bleaching of oxygen delignified Eucalyptus kraft pulps

The use of a novel “xylanase A” enzyme was found beneficial in the elemental chlorine free (ECF) bleaching of oxygen delignified Eucalyptus kraft pulps. The application of the enzyme made possible production of fully bleached pulps with high brightness (89% ISO) and viscosities (above 800 cm3/g), without elemental chlorine (XDnEpD and DnEpD sequences) at low chlorine dioxide consumption. As a result of the enzyme treatment, morphological changes such as cracks, flakes, filaments and peeling of the fibre cell wall were observed by SEM (scanning electron microscopy). These modifications of the fibre surface facilitated the access to the fibre cell wall for the successive bleaching with less chemicals.