Xylanase pre-treatment of giant reed organosolv pulps: Direct bleaching effect and bleach boosting

The effect of enzymatic pre-treatment with xylanase preparation (endo-1,4-β-xylanase activity; EC 3.2.1.8) on properties and bleachability of organic solvent-based Ethanol-Alkali, Organocell (alkali-anthraquinone-methanol) and ASAM (alkali-sulfite-anthraquinone-methanol) pulps produced from agro-fibre crop giant reed (Arundo donax L.) has been examined and compared with traditional kraft pulp. The enzyme-assisted removal of xylan-associated lignin fragments and hexenuronic acids caused direct brightening and delignification during the enzymatic stage, while somewhat affecting the pulp strength properties. The xylanase bleach boosting substantially improved subsequent chemical bleaching of organosolv pulps by hydrogen peroxide. The savings in bleaching chemicals with simultaneous increase in brightness and degree of delignification were observed. The enzymatic pre-treatment improved the intrinsic viscosity of bleached organosolv pulps.