A Biocatalytic One‐Pot Approach for the Preparation of Lignin Oligomers Using an Oxidase/Peroxidase Cascade Enzyme System

Abstract

Syntheticl ignin wasp reparedb iocatalytically in ao ne-pot, two-stepr eactionu sing an oxidase/peroxidasec ascade enzyme system. Using eugenoli nc ombination with eugenolo xidase and a peroxidase,l ignin-like material was produced. The cascade reactiont akes advantage of the ability of the oxidase to produce coniferyla lcohol and hydrogen peroxide from eugenola nd molecular oxygen. The hydrogenp eroxide is usedb yt he peroxidasef or the formation of crosslinks that typify lignin. As eugenol oxidase has ab road substrate acceptance profile, also 4-allylphenol (chavicol) and 4-allyl-2,6-dimethoxyphenol could be used as precursors of the synthetic lignin. As ar esult, all three naturally occurring monolignols couldb ep repared and incorporated in the synthetic lignin. Ther eaction was optimized in order to achievet he highest possible yield of insoluble lignin oligomers and scaled up to 1g ram.A nalysis of the water-insoluble product by gel permeation chromatography revealed the formation of relatively small lignin oligomers ( % 1000 dalton). By using twodimensional heteronuclear single quantum coherence nuclear magnetic resonance spectroscopy (2D HSQC NMR) analysis it could be demonstratedt hat the material contained a-O-4/b-O-4, b-O-4, b-b, b-5 linkages and dibenzodioxocin units.All these featuresindicate that the biocatalytically produced material closely resembles natural lignin. While 54% of eugenol wasc onverted into water-insoluble oligomers, the remaining substrate was converted into watersoluble dimersa nd tetramers which are important lignin model compounds.T herefore,t he presented method represents av aluable andf acile biocatalytic approachf or the preparation of lignin-like material and potentially valuable chemicals.

An Introduction to Model Compounds of Lignin Linking Motifs; Synthesis and Selection Considerations for Reactivity Studies

“…The most common approacht op repareD HP lignins (or DHPs) involves using HRP and hydrogen peroxide to polymerize mixtures of monolignols in buffered solutions as am imic for the biosynthesis of lignin in nature. [155][156][157][158][159][160] The advantages of this approach are that it generates the desired complex polymeri no ne step, and it should,i nt heory,i ntegrate all the knownl ignin linking motifs. Twom ain methods for the polymerization exists the so-called "zulauf"a nd the "zutropf" methods.…”

A Xylenol Orange-Based Screening Assay for the Substrate Specificity of Flavin-Dependent para-Phenol Oxidases

“…VAO can also be used for the synthesis of chiral secondary alcohols, with the oxidation of short-chain linear 4-alkylphenols yielding the ( R )-enantiomers of the corresponding alcohols in high enantiomeric excess [ 15 ]. The hydroxylation of 4-allylphenols by VAO or EUGO has been employed in multi-enzyme cascades for the synthesis of the plant lignan pinoresinol and model lignin compounds [ 16 , 17 , 18 ]. The hydroxylation of eugenol (4-allyl-2-methoxyphenol) by VAO has also garnered interest as the first step in fermentation processes for the conversion of eugenol to ferulic acid, which can be used as a precursor for vanillin [ 19 , 20 , 21 , 22 , 23 , 24 ].…”

Expression and Characterization of a Dye-Decolorizing Peroxidase from Pseudomonas Fluorescens Pf0-1

“…Considering the radical mechanism of laccases and peroxidases it is certain that the concerted action of several enzymes or trapping of produced radicals is needed to achieve depolymerization. Otherwise, depolymerization and repolymerization will occur, as demonstrated in recent publications of synthesis of lignin oligomers [11,32].…”

“…Several bacterial DyPs were found to be robust enzymes and thus potent biocatalysts [10][11][12]. Since they can degrade a variety of synthetic dyes, DyPs can potentially be used in the bioremediation of dye-contaminated waste water.…”