title: In vitro model assemblies to study the impact of lignin-carbohydrate interactions on the enzymatic conversion of xylan.
abstract: Endo-beta-1,4-xylanases (EC 3.2.1.8) are the main enzymes involved in the hydrolysis of xylans, the most abundant hemicelluloses in plant biomass. However, the development of efficient endoxylanases for use in biorefinery processes is currently hampered by insufficient knowledge regarding the impact of the cell wall network organization on the action of the enzyme at the supramolecular level. The action pattern of a GH11 endoxylanase from Thermobacillus xylanilyticus (Tx-xyl) was investigated by means of in vitro reconstituted model systems which can mimic certain cell wall structures. The action of Tx-xyl was evaluated on polymer assemblies displaying increasing complexity using delignified glucuronoarabinoxylan (GAX), then GAX-DHP model complexes obtained by oxidative polymerization of coniferyl alcohol into dehydrogenation polymers (DHP: lignin model compounds) in the presence of GAX. At a high concentration of GAX, interchain associations are formed leading to high molecular weight aggregates. These structures did not appear to affect the action of endoxylanase, which induces disaggregation of the self-aggregates along with polymer depolymerization. To mimic lignin-carbohydrate interactions, two different GAX-DHP nanocomposites were prepared and incubated with endoxylanase. In both cases, free GAX was hydrolyzed, while the GAX-DHP complexes appeared to be resistant. In the case of the noncovalently linked GAX-DHP(ZL) complexes, enzyme action favored a decrease in particle size, owing to the removal of their relatively exposed carbohydrate chains, whereas the complex supramolecular organization of the covalently linked GAX-DHP(ZT) complexes severely hampers the enzyme's access to carbohydrate. Overall, these results establish the negative impact of DHP on the endoxylanase action and provide new knowledge regarding the limitations of the enzyme action in the lignocellulose bioconversion processes.
authors: INRA, UMR 614, Fractionnement des AgroRessources et Environnement, F-51686 Reims, France.
authors: Imen
authors: I
authors: Boukari
authors: Jean-Luc
authors: JL
authors: Putaux
authors: Bernard
authors: B
authors: Cathala
authors: Abdellatif
authors: A
authors: Barakat
authors: Bodo
authors: B
authors: Saake
authors: Caroline
authors: C
authors: Rémond
authors: Michael
authors: M
authors: O'Donohue
authors: Brigitte
authors: B
authors: Chabbert
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D002236:Carbohydrate Conformation; D002241:Carbohydrates / Q000737:chemistry*; D043364:Endo-1,4-beta Xylanases / Q000378:metabolism*; D008031:Lignin / Q000737:chemistry*; D008958:Models, Molecular; D014990:Xylans / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D002241:Carbohydrates; D014990:Xylans; D008031:Lignin; D043364:Endo-1,4-beta Xylanases