title: Isolation and characterization of unhydrolyzed oligosaccharides from switchgrass (Panicum virgatum, L.) xylan after exhaustive enzymatic treatment with commercial enzyme preparations.
abstract: Switchgrass (Panicum virgatum, L.) is a potential renewable source of carbohydrates for use in microbial conversion to biofuels. Xylan comprises approximately 30% of the switchgrass cell wall. To understand the limitations of commercial enzyme mixtures, alkali-extracted, isolated switchgrass xylan was hydrolyzed by the action of two commercial enzyme cocktails, in the presence and absence of an additional α-arabinofuranosidase enzyme. The two most abundant enzymatic digestion products from each commercial enzyme treatment were separated and characterized by LC-MS(n), linkage analysis, and NMR. The most abundant oligosaccharide from each commercial cocktail was susceptible to hydrolysis when supplemented with a GH62 α-arabinofuranosidase enzyme; further characterization confirmed the presence of (1→3)-α-arabinose linkages. These results demonstrate the lack of the required selectivity for arabinose-containing substrates in the commercial enzyme preparations tested. One product from each condition remained intact and was found to contain (1→2)-β-xylose-(1→3)-α-arabinose side chains; this linkage acts as a source of oligosaccharide recalcitrance.
authors.affiliation: USDA, Agricultural Research Service, National Center for Agricultural Utilization Research, Bioenergy Research Unit, 1815 N. University Street, Peoria, IL 61604, USA(†). Electronic address: michael.bowman@ars.usda.gov.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Bowman
authors.affiliation: USDA, Agricultural Research Service, National Center for Agricultural Utilization Research, Bioenergy Research Unit, 1815 N. University Street, Peoria, IL 61604, USA(†).
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Dien
authors.affiliation: USDA, Agricultural Research Service, National Center for Agricultural Utilization Research, Functional Foods Research Unit, 1815 N. University Street, Peoria, IL 61604, USA(†).
authors.forename: Karl E
authors.initials: KE
authors.lastname: Vermillion
authors.affiliation: USDA, Agricultural Research Service, National Center for Agricultural Utilization Research, Bioenergy Research Unit, 1815 N. University Street, Peoria, IL 61604, USA(†).
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Mertens
mesh_terms: D001089:Arabinose / Q000737:chemistry; D002236:Carbohydrate Conformation; D006026:Glycoside Hydrolases / Q000378:metabolism*; D006868:Hydrolysis; D009844:Oligosaccharides / Q000737:chemistry* / Q000378:metabolism; D008897:Panicum / Q000737:chemistry* / Q000378:metabolism; D014990:Xylans / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D009844:Oligosaccharides; D014990:Xylans; D001089:Arabinose; D006026:Glycoside Hydrolases; C019713:alpha-N-arabinofuranosidase
keywords: LC-MS(n); Switchgrass; Xylan; Xylooligosaccharide; α-Arabinofuranosidase