High consistency mechano-enzymatic pretreatment for kraft fibres: effect of treatment consistency on fibre properties

Fibre reactivity is essential for cellulose dissolution and derivatisation and a porous fibre structure is one key determinant for a highly reactive pulp. Mechanical and enzymatic treatments are known to improve fibre reactivity and more recently, the combination of mechano-enzymatic treatment has been shown to synergistically enhance the beneficial effect. The aim of this work was to do a systematic study on the effect of dry matter content during enzymatic modification of fibres and define the conditions that optimally improve fibre porosity. The combined mechano-enzymatic treatments at 15–25 w% consistency had the most pronounced effect on fibre porosity and morphology analysed by solute exclusion technique, nitrogen sorption and scanning electron microscopy. Light microscopy imaging confirmed that the combined mechano-enzymatic treatment at high consistency (> 10 w%) resulted in extensive fibrillation of the treated fibres which was not observed after sole mechanical or enzymatic treatments.