Effect of laccase enzyme treatment on the strength properties of OCC pulp

Paper made of recycled fibers has less strength compared to virgin fibers due to the multiplicity of recycling. Several solutions have been proposed to solve this problem consist of specialized enzymes application. While the applications of enzymes in the pulp and paper industry is still in the research and development stage, but some of them have pioneered the technology to operate. There are various methods to increase recycled fiber bonding and improves the paper strength. Oxidant enzymes such as cellulase and laccase are one of the methods that could accelerate delignification. Laccase-mediator system has the greatest effect on increasing of paper strength according to previous studies. Common Low molecular weight of mediator such as ABTS or HBT are the best non-phenolic lignin oxidizing that have been used yet. In order to increase the strength of recycled paper the effect of laccase treatment on old corrugated container (OCC) pulp was investigated in this study. OCC pulp was obtained from headbox of recycled paper factory in the north of Iran (Afrang Noor), and then was fractionated by Bauer-McNett classifier. HBT mediator was selected to treatment of OCC pulp by laccase. The pulp was treated by the enzyme in the adjusted conditions including 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. Handsheet making and characteristic measurement carried out by TAPPI test methods and also statistical analysis was conducted using completely randomized design. Fiber classification result showed that fines constitute about 31% of weight of the pulp. There are significant differences at 1% level among the pulp strength properties of OCC which treated with laccase enzyme. Tensile and burst indices significantly were increased compared to the control using 0.005% of laccase. Multiple Duncan test showed that the average of these two indices by using 0.005% and 0.015% laccase (based on O.D. weight of pulp) had no significant difference and placed in the same statistical group. The variation trend of tear index unlike the other indices was observed and concora medium test (CMT) decreased at all levels of the treatments. OCC pulp treated with 0.005% laccase-HBT (based on O.D. weight of pulp) is recommended according to the important role of tensile and burst strength in test liner for packaging industry. Due to decreasing of Concora medium test (CMT) by the enzyme, laccase application is not suitable for making corrugated paper.