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Structural Motifs of Wheat Straw Lignin Differ in Susceptibility to Degradation by the White-Rot Fungus Ceriporiopsis subvermispora
journal contribution
posted on 2019-11-19, 16:44 authored by Gijs van Erven, Jianli Wang, Peicheng Sun, Pieter de Waard, Jacinta van der Putten, Guus E. Frissen, Richard J. A. Gosselink, Grigory Zinovyev, Antje Potthast, Willem J. H. van Berkel, Mirjam A. KabelThe white-rot fungus Ceriporiopsis subvermispora delignifies plant biomass extensively and selectively and, therefore,
has great biotechnological potential. We previously demonstrated that
after 7 weeks of fungal growth on wheat straw 70% w/w of lignin was
removed and established the underlying degradation mechanisms via
selectively extracted diagnostic substructures. In this work, we fractionated
the residual (more intact) lignin and comprehensively characterized
the obtained isolates to determine the susceptibility of wheat straw
lignin’s structural motifs to fungal degradation. Using 13C IS pyrolysis gas chromatography–mass spectrometry
(py-GC-MS), heteronuclear single quantum coherence (HSQC) and 31P NMR spectroscopy, and size-exclusion chromatography (SEC)
analyses, it was shown that β-O-4′ ethers
and the more condensed phenylcoumarans and resinols were equally susceptible
to fungal breakdown. Interestingly, for β-O-4′ ether substructures, marked cleavage preferences could
be observed: β-O-4′-syringyl substructures
were degraded more frequently than their β-O-4′-guaiacyl and β-O-4′-tricin
analogues. Furthermore, diastereochemistry (threo > erythro) and γ-acylation (γ-OH
>
γ-acyl) influenced cleavage susceptibility. These results indicate
that electron density of the 4′-O-coupled
ring and local steric hindrance are important determinants of oxidative
β-O-4′ ether degradation. Our findings
provide novel insight into the delignification mechanisms of C. subvermispora and contribute to improving the
valorization of lignocellulosic biomass.
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Keywords
electron densityStructural Motifs13 Clignocellulosic biomassOHcleavage susceptibilityWheat Straw Ligninβ-HSQCligninquantum coherence7 weeks31 P NMR spectroscopyethercleavage preferencesSECsize-exclusion chromatographydelignification mechanismswhite-rot fungus Ceriporiopsis subvermispora delignifies plant biomassnovel insightdegradation mechanismssteric hindranceγ- acylsubstructureWhite-Rot Fungus Ceriporiopsis subvermispora
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