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

Abstract

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-sulphonate) (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. Pulp viscosity, an indicator of cellulose chain length, was decreased only slightly by laccase. Thus the enzyme in the presence of ABTS, unlike the fungus, specifically attacks lignin.

The early oxidative biodegradation steps of residual kraft lignin models with laccase

“…Such reactivity patterns have already been observed for laccase oxidations of lignins and lignin model compounds. 2,15,19 This behaviour is analogous to the overall reactivity found between hydroxy radicals and lignin model compounds. This analogy is reasonable since the main intermediates involved in such reactions are believed to be phenoxy radicals.…”

“…Laccase alone, however, has little e ect on pulps, but when used in the presence of mediators such as 2,2 H -azinobis-(3-ethyl-benzthiazoline-6-sulfonate) (ABTS) or 1-hydroxybenzotriazole (HBT) laccase has been shown to e ectively demethylate kraft pulps. 2 In order to elucidate the deligni®cation mechanism catalyzed by laccase, several studies have been carried out on both phenolic and non-phenolic monomeric, arylglycerol b-O-4 and b-1 ether lignin model compounds. 3±5 The use of radical mediators has become of interest since the early report that non-phenolic lignin model compounds, unreactive towards laccase alone, could be oxidized in the presence of laccase and ABTS, 3 and that kraft pulp could be deligni®ed.…”

An acid-stable laccase from Sclerotium rolfsii with potential for wool dye decolourization

“…Laccases (benezenediol:oxygen oxidoreductase, EC 1.10.3.2) are multinuclear copper-containing enzymes that catalyse the oxidation of a variety of phenolic and inorganic compounds, with the concomitant reduction of oxygen to water [1]. Although primarily originating from fungi [2,3], laccases are widely distributed in nature and have also been detected in plants [4], insects [5] and bacteria [6].…”

Oxidation of Triacyiglycerol by Laccase-Natural Mediator and Laccase-Mediator Derived from Natural Compound Systems.

“…2,4-Dimethoxyphenol (DMP), syringic alcohol (SAlc), syringaldehyde (SAld), syringic acid (SAcid) and transferulic acid (FAcid) can be obtained from the lignin in wood. ABTS and HBT were used as typical synthetic mediators, because they have been reported as high performance mediators in many papers (2,(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)21,22). The results of the oxidation of LO by various reaction systems are shown in Fig.…”

“…Such processes have potential applications for biobleaching, i.e., degradation of lignin-containing phenol or benzyl alcohol derivatives (7)(8)(9)(10), and for bioremediation, e.g., oxidative degradation of PAHs (5,6,(11)(12)(13), estrogenic compounds (14) and dioxins (15) in the environment. In other words, oxidation reactions of these aromatic compounds by laccase/mediator systems can be solve the problems.…”