Can laccases catalyze bond cleavage in lignin?

Line Munk, Anna Katarzyna Sitarz, Dayanand Kalyani, Jørn Dalgaard Mikkelsen, Anne S. Meyer

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Modification of lignin is recognized as an important aspect of the successful refining of lignocellulosic biomass, and enzyme-assisted processing and upcycling of lignin is receiving significant attention in the literature. Laccases (EC 1.103.2) are taking the centerstage of this attention, since these enzymes may help degrading lignin, using oxygen as the oxidant. Laccases can catalyze polymerization of lignin, but the question is whether and how laccases can directly catalyze modification of lignin via catalytic bond cleavage. Via a thorough review of the available literature and detailed illustrations of the putative laccase catalyzed reactions, including the possible reactions of the reactive radical intermediates taking place after the initial oxidation of the phenol-hydroxyl groups, we show that i) Laccase activity is able to catalyze bond cleavage in low molecular weight phenolic lignin model compounds; ii) For laccases to catalyze inter-unit bond cleavage in lignin substrates, the presence of a mediator system is required. Clearly, the higher the redox potential of the laccase enzyme, the broader the range of substrates, including o- and p-diphenols, aminophenols, methoxy-substituted phenols, benzenethiols, polyphenols, and polyamines, which may be oxidized. In addition, the currently available analytical methods that can be used to detect enzyme catalyzed changes in lignin are summarized, and an improved nomenclature for unequivocal interpretation of the action of laccases on lignin is proposed. (C) 2015 Elsevier Inc. All rights reserved.
Original languageEnglish
JournalBiotechnology Advances
Volume33
Issue number1
Pages (from-to)13-24
Number of pages12
ISSN0734-9750
DOIs
Publication statusPublished - 2015

Keywords

  • Biocatalysis
  • Lignocellulose
  • Mediators
  • Oxidation
  • Catalysis
  • Lignin
  • Phenols
  • Reaction intermediates
  • Redox reactions
  • Refining
  • Catalyzed reactions
  • Lignin model compound
  • Lignocellulosic biomass
  • Low molecular weight
  • Phenol hydroxyl group
  • Enzymes
  • catalyzed reaction
  • enzyme activity
  • aminophenol 27598-85-2
  • benzenethiol 108-98-5
  • biofuel production
  • hydroxyl 3352-57-6
  • laccase 80498-15-3 EC 1.10.3.2 catalyst
  • lignin 9005-53-2
  • methoxy-substituted phenol
  • o-diphenol 1806-29-7
  • oxygen 7782-44-7
  • p-diphenol
  • phenol 108-95-2 oxidation
  • polyamine
  • polyphenol 27073-41-2
  • reactive radical intermediate
  • 10060, Biochemistry studies - General
  • 10802, Enzymes - General and comparative studies: coenzymes
  • 39008, Food microbiology - General and miscellaneous
  • Biochemistry and Molecular Biophysics
  • Bioprocess Engineering
  • Enzymology

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