Use of Feruloyl Esterase as Laccase-Mediator System in Paper Bleaching.

In order to bleach the eucalyptus kraft pulp, two enzyme treatments involving feruloyl esterase and laccase were used in the TCF sequence. Hydroxycinnamic acids, which were released from lignin subunits by the activity of feruloyl esterase, were used as a natural mediator of laccase. The use of sequentially feruloyl esterase and laccase has much higher pulp bleaching effects than the individual enzymes. GthFAE, BmegLac and GthFAE+BmegLac treatments (X) reduced the kappa number of eucalyptus kraft pulps by indicating 9%, 18%, and 30% delignification rates, respectively. Just like in delignification rates, the highest brightness improvement was achieved from the GthFAE+BmegLac combination. The results of the present study indicated that the natural mediators, which are presented in the structure of lignin, could be used as laccase-mediators for pulp bleaching more efficiently and cost-effectively.