Modification of pine kraft pulp using hydrolytic and oxidizing enzymes

Oxygen delignified pine kraft pulps were treated with lignin modifying enzymes: laccase (EC 1.10.3.2), Mn-dependent peroxidase (EC 1.11.1.x), lignin peroxidase (EC 1.11.1.y), and a xylanase (EC 3.2.1.8) in order to increase their bleachability. Pulps were treated either with a purified single enzyme or the enzymes were successively added in different combinations. The residual pulps were delignified with alkaline peroxide and analysed for kappa number and ISO-brightness. Xylanase treatment improved the reference brightness by 1 - 2.5 units and combination with lignin modifying enzymes improved the value by a further one unit. Lignin modifying enzymes when acting alone gave equal or even poorer pulp values than the reference.