Bioelectrocatalytic properties of lignin peroxidase from Phanerochaete chrysosporium in reactions with phenols, catechols and lignin-model compounds

Bioelectrocatalytic reduction of H2O2 catalysed by lignin peroxidase from Phanerochaete chrysosporium (LiP) was studied with LiP-modified graphite electrodes to elucidate the ability of UP to electro-enzymatically oxidise phenols, catechols, as well as veratryl alcohol (VA) and some other high-redox-potential lignin model compounds (LMC). Flow-through amperometric experiments performed at +0.1 V vs. Ag vertical bar AgCl demonstrated that UP displayed significant bioelectrocatalytic activity for the reduction of H2O2 both directly (i.e., in direct electron transfer (ET) reaction between LiP and the electrode) and using most of studied compounds acting as redox mediators in the UP bioelectrocatalytic cycle, with a pH optimum of 3.0. The bioelectrocatalytic reduction Of H2O2 mediated by VA and effects of VA on the efficiency of bioelectrocatalytic oxidation of other co-substrates acting as mediators were investigated. The bioelectrocatalytic oxidation of phenol- and catechol derivatives and 2,2'-azino-bis(3-ethyl-benzothiazoline-6-sulphonate) by UP was independent of the presence of VA, whereas the efficiency of the UP bioelectrocatalysis with the majority of other LMC acting as mediators increased upon addition of VA. Special cases were phenol and 4-methoxymandelic acid (4-MMA). Both phenol and 4-MMA suppressed the bioelectrocatalytic activity of UP below the direct ET level, which was, however, restored and increased in the presence of VA mediating the ET between UP and these two compounds. The obtained results suggest different mechanisms for the bioelectrocatalysis of UP depending on the chemical nature of the mediators and are of a special interest both for fundamental science and for application of LiP in biotechnological processes as solid-phase bio(electro)catalyst for decomposition/detection of recalcitrant aromatic compounds. (c) 2006 Elsevier B.V All rights reserved.