Research Of Laccase Improve Pulp Properties

The unbleached kraft pulp (KP) and old corrugated containers (OCC) pulp was treated by laccase and different compounds, including phenolic compound, amino acid and industrial lignin, for improving the strength properties of the resulting paper. The optimal enzyme treatment conditions were studied.The KP was treated by laccase and phenolic compounds, and the fiber quality and morphology were analyzed by FQA and SEM, respectively. The results showed that the pulp strengths were improved in different degree after laccase treatment with different compounds. However, the brightness of the resulting paper decreased. The hydroxybenzoic acid was the best compound for improving the dry strength of paper. The optimal reaction conditions were:laccase dosage of4U/g pulp, hydroxybenzoic acid dosage of3%(w/w), temperature of45℃and pH4.5. In addition, the fiber coarseness significantly increased and the fines content also increased. The adhesion of fiber in large areas was observed in the resulting paper.The effect of laccase/industrial lignin/compound treatment on the strengths of OCC pulp was studied. The results showed that the pulp strength was slightly improved after laccase alone treatment. The dry and wet strength were significantly enhanced when further adding the industrial lignin, especially alkali lignin. The laccase/industrial lignin treatment combined with different compounds, especially syringaldehyde and methyl syringate, could enhance the dry/wet strength of pulp. The optimal treatment conditions were:the pulp was treated by laccase and syringaldehyde for an hour and followed by adding industrial lignin to the reaction system for another an hour. The syringaldehyde dosage is0.3%and the dosage of alkaline lignin is0.2%(all relative to dry pulp).The dry tensile index and wet tensile index of KP pulp were also improved after laccase treatment with ferulic acid, tyrosine and chitosan. The dry and wet tensile index increased by4.9%and15.33%when histidine was used. In addition, the effect of the phenolic compound on wheat pulp bleachability was discussed. The results showed that the bleachability of pulp was improved with laccase/phenolic compounds treatment and following alkali treatment, however, the pulp strength decreased. Both the bleachability and the strength of pulp could be improved without alkali treatment.