|Title||Structural Motifs of Wheat Straw Lignin Differ in Susceptibility to Degradation by the White-Rot Fungus Ceriporiopsis subvermispora|
|Author(s)||Erven, Gijs Van; Wang, Jianli; Sun, Peicheng; Waard, Pieter De; Putten, Jacinta Van Der; Frissen, Guus E.; Gosselink, Richard J.A.; Zinovyev, Grigory; Potthast, Antje; Berkel, Willem J.H. Van; Kabel, Mirjam A.|
|Source||ACS sustainable chemistry & engineering 7 (2019)24. - ISSN 2168-0485 - p. 20032 - 20042.|
BBP Biorefinery & Sustainable Value Chains
BBP Sustainable Chemistry & Technology
|Publication type||Refereed Article in a scientific journal|
|Keyword(s)||biological pretreatment - lignin quantification - ligninolysis - NMR spectroscopy - oxidation - selective delignification - single-electron transfer - stereoselectivity|
The 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.