Demethylation and delignification of kraft pulp by Trametes versicolor laccase in the presence of 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate)

Bleaching of hardwood kraft pulp by Trametes versicolor was accompanied by release and accumulation of methanol, which was produced by demethylation of the pulp. A partial demethylation of the pulp was observed with isolated laccase I from T. versicolor . The extent of demethylation by laccase was increased to the level released by the fungus by addition of 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulponate) (ABTS). Methanol release by the laccase/ABTS combination was followed by slower kappa reduction. Both methanol release and kappa reduction were dependent on laccase and ABTS concentrations. The fungus did not produce a stable equivalent of ABTS during bleaching, because extracellular culture fluid from bleaching cultures gave only the same methanol release from pulp as laccase I.