IMPROVING THE PROPERTIES OF KRAFT PULP WITH LACCASE/p-COUMARIC ACID

Mediators enhance the oxidative capabilities of laccase allowing the oxidation of high-redox potential aromatic compounds. But the major limited factors for application of laccase in paper making are synthetic mediators' high price and toxic properties. The advantages of using natural mediators reside in their low cost, lack of toxicity and they are obtained from natural, renewable sources. In this paper, p-coumaric acid was used to explore the role of natural mediator in the laccase/p-coumaric acid system. The treated kraft pulps were analyzed for many characteristics, such as kappa numbers, the surface feature of fibers, morphological properties of fibers and physical properties of handsheets. The results showed that the kappa number of pulp treated with laccase/p-coumaric acid increased by 10.76% compared with that of control sample. However, there were little difference between the kappa numbers of pulps treated with laccase and the control sample. Meanwhile, the coarseness of fibers treated with laccase/p-coumaric acid increased by 10.58%. But the coarseness of fibers treated with laccase was decreased by 21.81%. The SEM results of sample treated with laccase showed that the structures of handsheets were compact, adhesion phenomenon occurred among fibers, and the surface of fibers turned rough. The SEM image treated with laccase/p-coumaric acid showedthat more adhesion phenomenon occurred among fibers, and the surface of fibers became smooth. Wet tensile strength and wet ring crush strength of handsheets treated with laccase/p-coumaric acid increased by 9.52% and 20.95% respectively, compared with those of control sample.