title: Studies of xylan interactions and cross-linking to synthetic lignins formed by bulk and end-wise polymerization: a model study of lignin carbohydrate complex formation.
abstract: The mechanism of lignin carbohydrate complex formation by addition of polysaccharides on quinone methide (QM) generated during lignin polymerisation was investigated using a model approach. Dehydrogenation polymers (DHPs, lignin model compounds) were synthesized from coniferyl alcohol in the presence of a glucuronoarabinoxylan (GAX) extracted from oat spelts, by Zutropfverfahren (ZT) and Zulaufverfahren (ZL) methods. The methods ZT and ZL differed in their distribution of QM over the reaction period but generated roughly the same QM amount. Steric exclusion chromatography of the ZT and ZL reaction products showed that only the ZT reaction produced high molar mass compounds. Covalent linkages in the ZT reaction involving ether bonds between GAX moiety and alpha carbon of the lignin monomer were confirmed by (13)C NMR and xylanase-based fractionation. The underlying phenomena were further investigated by examining the interactions between GAX and DHP in sorption experiments. GAX and DHPs were shown to interact to form hydrophobic aggregates. In the ZT process, slow addition permitted polymer reorganisation which led to dehydration around the lignin-like growing chains thereby limiting the addition of water on the quinone methide formed during polymerisation and thus favoured lignin-carbohydrate complex (LCC) formation.
authors.affiliation: Unité Mixte de Recherche Fractionnement des AgroRessources et Emballages, Institut National de la Recherche Agronomique, Equipe Parois et Matériaux Fibreux, 51686, Reims Cedex 2, France.
authors.forename: Abdellatif
authors.initials: A
authors.lastname: Barakat
authors.forename: Heiko
authors.initials: H
authors.lastname: Winter
authors.forename: Corinne
authors.initials: C
authors.lastname: Rondeau-Mouro
authors.forename: Bodo
authors.initials: B
authors.lastname: Saake
authors.forename: Brigitte
authors.initials: B
authors.lastname: Chabbert
authors.forename: Bernard
authors.initials: B
authors.lastname: Cathala
mesh_terms: D018554:Avena / Q000378:metabolism*; D002850:Chromatography, Gel; D057927:Hydrophobic and Hydrophilic Interactions; D008031:Lignin / Q000737:chemistry / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D010636:Phenols / Q000737:chemistry / Q000378:metabolism; D014990:Xylans / Q000737:chemistry / Q000378:metabolism*
chemical_list: D010636:Phenols; D014990:Xylans; C114470:glucuronoarabinoxylan; D008031:Lignin; C010559:coniferyl alcohol