Influence of mediators on laccase catalyzed radical formation in lignin

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Influence of mediators on laccase catalyzed radical formation in lignin. / Munk, Line; Andersen, Mogens Larsen; Meyer, Anne S.

In: Enzyme and Microbial Technology, Vol. 116, 2018, p. 48-56.

Research output: Contribution to journalJournal article – Annual report year: 2018Researchpeer-review

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@article{c1ef18eec842442ba3e1fcd343b715c5,
title = "Influence of mediators on laccase catalyzed radical formation in lignin",
abstract = "Laccases (EC 1.10.3.2) catalyze oxidation of phenolic groups in lignin to phenoxyl radicals during reduction of O2 to H2O. Here, we examine the influence on this radical formation of mediators which are presumed to act by shuttling electrons between the laccase and the subunits in lignin that the enzyme cannot approach directly. Treatments of three different lignins with laccase-mediator-systems (LMS) including laccases derived from Trametes versicolor and Myceliophthora thermophila, respectively, and four individual mediators, 1-hydroxybenzotriazole (HBT), N-hydroxyphthalimide (HPI), 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO), and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) were assessed by real time electron paramagnetic resonance measurements. Radical steady state concentrations and radical formation rates were quantified. LMS treatments with 500 μM N-OH type mediators (HPI or HBT) did not affect the lignin radical formation, but increased doses of those mediators (5 mM) surprisingly led to significantly decreased radical formation rates and lowered steady state radical concentrations. Laccase-TEMPO treatment at a 5 mM mediator dose was the only system that significantly increased steady state radical concentration and rate of radical formation in beech organosolv lignin. The data suggest that electron shuttling by mediators is not a significant general mechanism for enhancing laccase catalyzed oxidation of biorefinery lignin substrates, and the results thus provide a new view on laccase catalyzed lignin modification.",
keywords = "ABTS, Electron paramagnetic resonance (EPR), HBT, HPI, Laccase-mediator systems, Myceliophthora thermophila, TEMPO, Trametes versicolor",
author = "Line Munk and Andersen, {Mogens Larsen} and Meyer, {Anne S.}",
year = "2018",
doi = "10.1016/j.enzmictec.2018.05.009",
language = "English",
volume = "116",
pages = "48--56",
journal = "Enzyme and Microbial Technology",
issn = "0141-0229",
publisher = "Elsevier",

}

RIS

TY - JOUR

T1 - Influence of mediators on laccase catalyzed radical formation in lignin

AU - Munk, Line

AU - Andersen, Mogens Larsen

AU - Meyer, Anne S.

PY - 2018

Y1 - 2018

N2 - Laccases (EC 1.10.3.2) catalyze oxidation of phenolic groups in lignin to phenoxyl radicals during reduction of O2 to H2O. Here, we examine the influence on this radical formation of mediators which are presumed to act by shuttling electrons between the laccase and the subunits in lignin that the enzyme cannot approach directly. Treatments of three different lignins with laccase-mediator-systems (LMS) including laccases derived from Trametes versicolor and Myceliophthora thermophila, respectively, and four individual mediators, 1-hydroxybenzotriazole (HBT), N-hydroxyphthalimide (HPI), 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO), and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) were assessed by real time electron paramagnetic resonance measurements. Radical steady state concentrations and radical formation rates were quantified. LMS treatments with 500 μM N-OH type mediators (HPI or HBT) did not affect the lignin radical formation, but increased doses of those mediators (5 mM) surprisingly led to significantly decreased radical formation rates and lowered steady state radical concentrations. Laccase-TEMPO treatment at a 5 mM mediator dose was the only system that significantly increased steady state radical concentration and rate of radical formation in beech organosolv lignin. The data suggest that electron shuttling by mediators is not a significant general mechanism for enhancing laccase catalyzed oxidation of biorefinery lignin substrates, and the results thus provide a new view on laccase catalyzed lignin modification.

AB - Laccases (EC 1.10.3.2) catalyze oxidation of phenolic groups in lignin to phenoxyl radicals during reduction of O2 to H2O. Here, we examine the influence on this radical formation of mediators which are presumed to act by shuttling electrons between the laccase and the subunits in lignin that the enzyme cannot approach directly. Treatments of three different lignins with laccase-mediator-systems (LMS) including laccases derived from Trametes versicolor and Myceliophthora thermophila, respectively, and four individual mediators, 1-hydroxybenzotriazole (HBT), N-hydroxyphthalimide (HPI), 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO), and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) were assessed by real time electron paramagnetic resonance measurements. Radical steady state concentrations and radical formation rates were quantified. LMS treatments with 500 μM N-OH type mediators (HPI or HBT) did not affect the lignin radical formation, but increased doses of those mediators (5 mM) surprisingly led to significantly decreased radical formation rates and lowered steady state radical concentrations. Laccase-TEMPO treatment at a 5 mM mediator dose was the only system that significantly increased steady state radical concentration and rate of radical formation in beech organosolv lignin. The data suggest that electron shuttling by mediators is not a significant general mechanism for enhancing laccase catalyzed oxidation of biorefinery lignin substrates, and the results thus provide a new view on laccase catalyzed lignin modification.

KW - ABTS

KW - Electron paramagnetic resonance (EPR)

KW - HBT

KW - HPI

KW - Laccase-mediator systems

KW - Myceliophthora thermophila

KW - TEMPO

KW - Trametes versicolor

U2 - 10.1016/j.enzmictec.2018.05.009

DO - 10.1016/j.enzmictec.2018.05.009

M3 - Journal article

VL - 116

SP - 48

EP - 56

JO - Enzyme and Microbial Technology

JF - Enzyme and Microbial Technology

SN - 0141-0229

ER -