Can laccases catalyze bond cleavage in lignin?

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

doi:10.1016/j.biotechadv.2014.12.008

Cited by 318 publications

(234 citation statements)

References 100 publications

Supporting

Mentioning

215

Contrasting

Unclassified

Order By: Relevance

“…[155] In these instances,t he reaction was suggested to involve ao ne-electron transport chain from the active site to the enzyme surface. [155,156] Despite the key roles of peroxidases and laccases in initiating the polymerisation, lignification per se is not an enzyme/ protein-controlled process.Infact, lignification is a"solutionlike" chemical process,a se videnced by the lack of optical activity in native lignins. [155,157] This fact implies that lignification neither occurs in the proximity of an enantioselective enzyme cavity nor is affected by the chiral environment of the surrounding polysaccharides.…”

Section: Structural Features Of Native Ligninsmentioning

confidence: 99%

Paving the Way for Lignin Valorisation: Recent Advances in Bioengineering, Biorefining and Catalysis

et al. 2016

View full text Add to dashboard Cite

Lignin is an abundant biopolymer with a high carbon content and high aromaticity. Despite its potential as a raw material for the fuel and chemical industries, lignin remains the most poorly utilised of the lignocellulosic biopolymers. Effective valorisation of lignin requires careful fine‐tuning of multiple “upstream” (i.e., lignin bioengineering, lignin isolation and “early‐stage catalytic conversion of lignin”) and “downstream” (i.e., lignin depolymerisation and upgrading) process stages, demanding input and understanding from a broad array of scientific disciplines. This review provides a “beginning‐to‐end” analysis of the recent advances reported in lignin valorisation. Particular emphasis is placed on the improved understanding of lignin's biosynthesis and structure, differences in structure and chemical bonding between native and technical lignins, emerging catalytic valorisation strategies, and the relationships between lignin structure and catalyst performance.

show abstract

Section: Structural Features Of Native Ligninsmentioning

confidence: 99%

Paving the Way for Lignin Valorisation: Recent Advances in Bioengineering, Biorefining and Catalysis

et al. 2016

View full text Add to dashboard Cite

show abstract

“…The potential applications of laccases in lignocellulose degradation have been comprehensively reviewed. 14,15 The remaining enzymes that support lignin degradation are known as accessory enzymes. 3 These include enzymes that produce hydrogen peroxide and enzymes that reduce methoxy radicals generated by the peroxidases and laccases.…”

Section: Cmentioning

confidence: 99%

Progress and obstacles in the production and application of recombinant lignin-degrading peroxidases

et al. 2016

View full text Add to dashboard Cite

Lignin is 1 of the 3 major components of lignocellulose. Its polymeric structure includes aromatic subunits that can be converted into high-value-added products, but this potential cannot yet been fully exploited because lignin is highly recalcitrant to degradation. Different approaches for the depolymerization of lignin have been tested, including pyrolysis, chemical oxidation, and hydrolysis under supercritical conditions. An additional strategy is the use of lignin-degrading enzymes, which imitates the natural degradation process. A versatile set of enzymes for lignin degradation has been identified, and research has focused on the production of recombinant enzymes in sufficient amounts to characterize their structure and reaction mechanisms. Enzymes have been analyzed individually and in combinations using artificial substrates, lignin model compounds, lignin and lignocellulose. Here we consider progress in the production of recombinant lignin-degrading peroxidases, the advantages and disadvantages of different expression hosts, and obstacles that must be overcome before such enzymes can be characterized and used for the industrial processing of lignin.

show abstract

“…Laccase catalysed action on lignin leads to phenoxy radicals which in turn induce a variety of non-enzymatic reactions including radical polymerization, bond cleavage, grafting, and modification of functional groups -all reactions which may be harnessed to functionalize lignin [12][13][14][15]. Elegant screening assays for enzymatic lignin oxidation have been reported [16,17], but unfortunately, these assays as well as detailed kinetic studies of laccases employ soluble phenols (monomeric and dimeric lignin model compounds) or are based on substrates such as ABTS (2,2'-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) or syringaldazine (4-hydroxy-3,5-dimethoxy-benzaldehyde azine) which relate poorly to lignin with respect to molecular weight, solubility, and chemical composition.…”

Section: Introductionmentioning

confidence: 99%

Direct rate assessment of laccase catalysed radical formation in lignin by electron paramagnetic resonance spectroscopy

Munk

Andersen

Meyer

2017

Enzyme and Microbial Technology

Self Cite

View full text Add to dashboard Cite

Highlights Time course EPR measurement of direct radical formation by fungal laccases on genuine lignin samples  Assessment of enzyme kinetic rates of radical formation in lignin by two fungal laccases  Identification of different radical formation patterns by a low and high redox potential laccase  Demonstration of different laccase rates on different types of lignin substrates Abstract Laccases (EC 1.10.3.2) catalyse removal of an electron and a proton from phenolic hydroxyl groups, including phenolic hydroxyls in lignins, to form phenoxy radicals during reduction of O2. We employed electron paramagnetic resonance spectroscopy (EPR) for real time measurement of such catalytic radical 2 formation activity on three types of lignin (two types of organosolv lignin, and a lignin rich residue from wheat straw hydrolysis) brought about by two different fungal laccases, derived from Trametes versicolor (Tv) and Myceliophthora thermophila (Mt), respectively. Laccase addition to suspensions of the individual lignin samples produced immediate time and enzyme dose dependent increases in intensity in the EPR signal with g-values in the range 2.0047-2.0050 allowing a direct quantitative monitoring of the radical formation and thus allowed laccase enzyme kinetics assessment on lignin. The experimental data verified that the laccases acted upon the insoluble lignin substrates in the suspensions. When the action on the lignin substrates of the two laccases were compared on equal enzyme dosage levels (by activity units on syringaldazine) the Mt laccase exerted a significantly faster radical formation than the Tv laccase on all three types of lignin substrates. When comparing the equal laccase dose rates on the three lignin substrates the enzymatic radical formation rate on the wheat straw lignin residue was consistently higher than that of the organosolv lignins. The pH-temperature optimum for the radical formation rate in organosolv lignin was determined by response surface methodology to pH 4.8, 33°C and pH 5.8, 33°C for the Tv laccase and the Mt laccase, respectively. The results verify direct radical formation action of fungal laccases on lignin without addition of mediators and the EPR methodology provides a new type of enzyme assay of laccases on lignin.

show abstract

Can laccases catalyze bond cleavage in lignin?

Cited by 318 publications

References 100 publications

Paving the Way for Lignin Valorisation: Recent Advances in Bioengineering, Biorefining and Catalysis

Paving the Way for Lignin Valorisation: Recent Advances in Bioengineering, Biorefining and Catalysis

Progress and obstacles in the production and application of recombinant lignin-degrading peroxidases

Direct rate assessment of laccase catalysed radical formation in lignin by electron paramagnetic resonance spectroscopy

Contact Info

Product

Resources

About