Effect of Lactase Enzyme on Delignification and Physical Properties of OCC Pulp

Old Corrugated Container (OCC) recycled pulp provided by a local paper manufacturing company was treated by lactase enzyme. The pulp was sampled from headbox and treated by enzyme in the conditions of consistency 2%، pH 5، reaction time 2 hours، and reaction temperature 60 °C in dosing levels of 0. 005، 0. 01 and 0. 015 % based on oven-dried weight of pulp. Fiber classification of the control pulp showed 31. 3 % of fines content and 0. 82 mm average fiber length. Results have indicated that lactase treatment decreased kappa number and SR degree to 20% and 14 degrees، respectively which consequently facilitated the drainage of pulp. The extraction of treated samples showed a peak at around 280 nm، confirming the delignification of pulp by enzyme. Microscopic observation of fiber walls of the treated sample indicated a local separation of middle lamella، fiber linting and removal of fines from fiber surface. The highest Water Retention Value (WRV) was measured to be at 0. 015% enzyme addition level. The apparent density of handsheets made from treated samples was lower compared with the handsheets made of control pulp resulting in loss of paper strengths.