Developing energy efficient lignin biomass processing – towards understanding mediator behaviour in ionic liquids

Eshtaya, Majd; Ejigu, Andinet; Stephens, Gill; Walsh, Darren A.; Croft, Anna K.

doi:10.1039/c5fd00226e

Cited by 13 publications

(12 citation statements)

References 56 publications

(115 reference statements)

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“…Liu et al [ 12 ] found that the stability of the ABTS + was higher in the presence of [Emim]EtSO 4 than [Emim]MeSO 4 , [Emim]Ac, or [Emim]DMP at pH 4.5, which was in accordance with our results. Eshtaya et al [ 34 ] also reported the compatibility of [Emim]EtSO 4 with ABTS + and used them in combination for electrochemical oxidation of lignin. In this work, the contribution of ABTS + scavenging was found to not be a critical factor in LS-induced inhibition; however, it should be taken into consideration when using the laccase/ABTS system for longstanding reactions.…”

Section: Discussionmentioning

confidence: 99%

Molecular Mechanisms Underlying Inhibitory Binding of Alkylimidazolium Ionic Liquids to Laccase

et al. 2017

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Water-miscible alkylimidazolium ionic liquids (ILs) are “green” co-solvents for laccase catalysis, but generally inhibit enzyme activity. Here, we present novel insights into inhibition mechanisms by a combination of enzyme kinetics analysis and molecular simulation. Alkylimidazolium cations competitively bound to the TI Cu active pocket in the laccase through hydrophobic interactions. Cations with shorter alkyl chains (C2~C6) entered the channel inside the pocket, exhibiting a high compatibility with laccase (competitive inhibition constant Kic = 3.36~3.83 mM). Under the same conditions, [Omim]Cl (Kic = 2.15 mM) and [Dmim]Cl (Kic = 0.18 mM) with longer alkyl chains bound with Leu296 or Leu297 near the pocket edge and Leu429 around TI Cu, which resulted in stronger inhibition. Complexation with alkylimidazolium cations shifted the pH optima of laccase to the right by 0.5 unit, and might, thereby, lead to invalidation of the Hofmeister series of anions. EtSO4− showed higher biocompatibility than did Ac− or Cl−, probably due to its binding near the TI Cu and its hindering the entry of alkylimidazolium cations. In addition, all tested ILs accelerated the scavenging of 2, 2′-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radicals, which, however, did not play a determining role in the inhibition of laccase.

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Section: Discussionmentioning

confidence: 99%

Molecular Mechanisms Underlying Inhibitory Binding of Alkylimidazolium Ionic Liquids to Laccase

et al. 2017

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“…ILs have excellent capability of solubilizing lignin during biomass pretreatment. 45 We expect that laccases and ILs might open the door of sustainable biomass engineering.…”

Section: ■ Conclusion and Future Perspectivesmentioning

confidence: 99%

“…44 Croft and co-workers investigated the mediator behavior in ionic liquids for developing lignin degradation during biomass processing. 45 As already mentioned, laccase-mediated reactions are basically the single-electron oxidation of phenols or amines using molecular oxygen. Since oxygen dissolves well in many ILs, it is expected that ILs are suitable solvents for laccase-catalyzed reactions.…”

Section: ■ Introductionmentioning

confidence: 99%

Laccase-Catalyzed Reactions in Ionic Liquids for Green Sustainable Chemistry

Itoh

Takagi

2020

ACS Sustainable Chem. Eng.

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Biocatalysis is an important and enabling tool in organic synthesis, degradation of chemical compounds, and biosensors. Laccases are copper ions containing oxidase and catalyze the conversion of polyphenol or amine derivatives using molecular oxygen. Recently, significant interests have gained attention for the development of a biochemical degradation method of lignocellulosic materials from the standpoint of green sustainable chemistry. Since these compounds are highly oxidized compounds, it is difficult to convert them stereo-or chemo-selectively to high-value small molecules. Chemical oxidations generally require hazardous reagents and harsh reaction conditions; hence, the resulting produced compounds are generally low-value molecules or complicated mixtures. On the contrary, laccases allow hazardous-reagent-free highly selective oxidative chemical conversions. The reactivity of the enzymes is influenced by a set of reaction conditions, in particular, the solvent system. Ionic liquids (ILs) have now been acknowledged as useful reaction media for biotransformations. Laccase-mediated reactions in ILs have been reviewed and focused on four topics: the first is "laccase-catalyzed reactions in ILs". The second is "biosensor system using laccase-mediated reaction in ILs". The third is "improved stability of laccase by immobilization or IL type additives", and the last chapter is "improved activity of laccase in ILs by protein engineering". Our opinion toward future perspectives of laccase-mediated reactions has also been discussed in "conclusions and future perspectives".

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“…RTIL have been used for catalytic lignin depolymerisation 30 – 32 . In addition, the RTIL’s ability to dissolve significant amounts of raw lignin material 33 – 35 , its thermal stability 36 , promoting free radical reactions 37 and its energy efficiency for biomass processing 38 have promoted RTIL as promising electrolytes for lignin decomposition. Electrochemical decomposition using triethylammonium methanesulfonate as RTIL resulted in conversion rates of 3–6% (w/w) for low cell voltages (1–1.5 V) 39 , but increased to 20% (w/w) near the upper limit of the ionic liquid (1.7 V) 40 .…”

Section: Introductionmentioning

confidence: 99%

Sustainable Electrochemical Depolymerization of Lignin in Reusable Ionic Liquids

Dier

Rauber

Durneata

et al. 2017

Sci Rep

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Lignin’s aromatic building blocks provide a chemical resource that is, in theory, ideal for substitution of aromatic petrochemicals. Moreover, degradation and valorization of lignin has the potential to generate many high-value chemicals for technical applications. In this study, electrochemical degradation of alkali and Organosolv lignin was performed using the ionic liquids 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and triethylammonium methanesulfonate. The extensive degradation of the investigated lignins with simultaneous almost full recovery of the electrolyte materials provided a sustainable alternative to more common lignin degradation processes. We demonstrate here that both the presence (and the absence) of water during electrolysis and proton transport reactions had significant impact on the degradation efficiency. Hydrogen peroxide radical formation promoted certain electrochemical mechanisms in electrolyte systems “contaminated” with water and increased yields of low molecular weight products significantly. The proposed mechanisms were tentatively confirmed by determining product distributions using a combination of liquid chromatography-mass spectrometry and gas-chromatography-mass spectrometry, allowing measurement of both polar versus non-polar as well as volatile versus non-volatile components in the mixtures.

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Developing energy efficient lignin biomass processing – towards understanding mediator behaviour in ionic liquids

Cited by 13 publications

References 56 publications

Molecular Mechanisms Underlying Inhibitory Binding of Alkylimidazolium Ionic Liquids to Laccase

Molecular Mechanisms Underlying Inhibitory Binding of Alkylimidazolium Ionic Liquids to Laccase

Laccase-Catalyzed Reactions in Ionic Liquids for Green Sustainable Chemistry

Sustainable Electrochemical Depolymerization of Lignin in Reusable Ionic Liquids

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