Alkylphenol oxidation with a laccase from a white-rot fungus: Effects of culture induction and of ABTS used as a mediator

Abstract

We investigated the potential of the laccase from the white-rot fungus Marasmius quercophilus to transform certain alkylphenols (p-nonylphenol, p-octylphenol and p-t-octylphenol). We tested the reactivity of this enzyme under different conditions: in liquid cultures and using the partially purified laccase with and without 2,2'-azino-bis-3-ehtylbenzothiazoline-6-sulfonicacid (ABTS) as a mediator. The percentage of p-t-octylphenol disappearance in liquid cultures was 69.0 ± 1.5% and 81 ± 5% after a 8-d or 15-d incubation, respectively, with p-nonylphenol, these percentages were 62 ± 4% and 91 ± 6% and with p-octylphenol 37 ± 3% and 65 ± 1% after a 15-d and a 21-d incubations, respectively. Induced pre-cultures were also used to inoculate the liquid cultures to enhance p-octylphenol transformation: the percentages of disappearance were 91.0 ± 0.5% and 97 ± 1% after a 8-d and a 15-d incubation, respectively. Mass spectrometry analysis showed that the products of oxidation of p-octylphenol were dimers with a mass of 411 m/z. Furthermore, we identified a purple compound (m/z 476) formed when ABTS was added to the reaction medium with the purified laccase. This result confirms that, in complex environments such as soils or litters where many molecules can interact with the enzyme substrate or the product of oxidation, laccase activities and those of other phenoloxidases should not be measured with ABTS.

Pre-treatment of a sugarcane bagasse-based substrate prior to saccharification: Effect of coffee pulp and urea on laccase and cellulase activities of Pycnoporus sanguineus

“…Collins et al (1996) observed induction of different isoforms of phenoloxidases by lignin-related phenols. Farnet et al (1999Farnet et al ( , 2011 found that different phenolic compounds like ferulic acid, gallic acid, vanillic acid or p-OH benzoic acid increased the number of isoforms produced by the white-rot fungus Marasmius quercophilus compared with control. Laccases from this white-rot fungus were also found to be induced by different aromatic pollutants like anthracene, and this resulted in a better degradation of the toxic compound (Qasemian et al, 2011).…”

Identification of various laccases induced by anthracene and contribution to its degradation in a Mediterranean coastal pine litter

“…They are known to produce phenoloxidases (Baldrian, 2006;Sinsabaugh, 2010): lignin peroxidase (LiP) (Hammel et al, 1986), manganese peroxidase (MnP) (Sack et al, 1997) and laccase (Collins et al, 1996). Previous studies have shown that laccases (benzenediol: oxygen oxidoreductase, EC 1.10.3.2) produced by white-rot fungi isolated from these particular ecosystems (Farnet et al, 2009(Farnet et al, , 2011 were able to transform various aromatic pollutants (Potin et al, 2004;Pozdnyakova et al, 2006;Majeau et al, 2010;Oria-de-Rueda et al, 2010). It therefore seems likely that this enzyme has major potential for anthracene transformation in Mediterranean coastal litters.…”

Enzyme-triggered Radical Reactions: Another Approach For Tin-free Radical Chemistry

“…However the modest yield and the quantity of mediator used in the process, 0.6 equiv., confirmed previous observations that ABTS might give rise to byproducts and therefore it was not the best mediator for a selective reaction. [24] In summary, this preliminary study showed that the couple laccase/mediator, with dioxygen as co-oxidant, is a viable alternative to initiate a radical reaction involving a redox process. This new method of radical generation enables the formation, at 30°C, of C-C bond and subsequent functionalization.…”