Degradation of anthracene by laccase of Trametes versicolor in the presence of different mediator compounds

Abstract

Laccase of Trametes versicolor was generally able to oxidize anthracene in vitro. After 72 h incubation about 35% of the anthracene was transformed stoichiometrically to 9,10-anthraquinone. Transformation of anthracene increased rapidly in the presence of different mediators that readily generate stable radicals: 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) and 1-hydroxybenzotriazole. For the reaction, the presence of both the laccase and the mediator was necessary. In the presence of 0.005 mM 1-hydroxybenzotriazole this conversion had removed 47% of the anthracene after 72 h; 75% of the substrate was oxidized during this period when ABTS (1 mM) was used as mediator. In contrast to reactions without or with only low concentrations of a mediator, there was a discrepancy between the disappearance of anthracene and the formation of 9,10-anthraquinone in mediator-forced reactions. Coupling-products of mediators with anthracene degradation products were found. Anthracene disappeared nearly completely after incubation for 72 h with laccase in a 0.1 mM solution of 1-hydroxybenzotriazole and was transformed to 9,10-anthraquinone in about 80% yield; 90% of the substrate was transformed in the presence of ABTS (2.0 mM) resulting again in 80% quinone. Phenothiazine was not effective in this system.

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.…”

Bioremediation of phenanthrene, chrysene and benzo[a]pyrene by fungi screened from nature

“…Phenanthrene was removed to 89% from the reaction mixture during the 72 h incubation, followed by chrysene and benzo[a]pyrene which were oxidized to 66% and 55%, respectively. The oxidation of chrysene and benzo[a]pyrene was reported to be considerably enhanced by the addition of mediator compounds [12,13]. 1-Hydroxybenzotriazole displayed an especially high increase in the reaction rate.…”

Wood production, wood technology, and biotechnological impacts

“…This circumstance hinders the application of laccase in lignin-biotechnology since in natural lignin most of the phenolic groups are substituted . Luckily, the detection of laccase mediators, small organic molecules with a high redox-potential (Bourbonnais & Paice 1990, Eggert et al 2006, Johannes et al 1996, Majcherczyk et al 1998, opened up chemical solutions to overcome weak properties of laccases (Call & Mücke 1997). Application of mediators enhances laccase reaction speeds and, most importantly, the substrate spectrum of the enzymes broadens dramatically.…”

“…Diverse xenobiotic compounds like chlorophenols (Leontievsky et al 2001), synthetic dyes (Rodriguez et al 1999), herbicides (Mougin et al 2000), non-phenolic aromatic hydrocarbons (Johannes et al 1996) and many other toxic organic pollutants , Nyanhongo et al 2007) were shown to be oxidised by laccases. Furthermore, the use of mediators greatly extends the range of degradable substances .…”