Xylooligosaccharides from steam-exploded barley straw: Structural features and assessment of bifidogenic properties

The biorefinery concept integrates the production of energy and bioproducts from biomass. In this philosophy, barley straw samples were used as raw material for the production of xylooligosaccharides (XOS) mixtures from soluble hemicelluloses by steam-explosion pretreatment. This fraction was treated by ion-exchange (XOS1) and a combination of membrane filtration, enzymatic hydrolysis, and ion-exchange processes (XOS2) to produce prebiotic compounds. The afforded products were then characterized by using analytical techniques, including HPAEC-PAD, FTIR, and MALDI-TOF-MS. XOS2 is composed of a back-bone of xylopyranosyl branched, which including acetyl-esterified oligosaccharides and feruloyl substituted arabino-oligosaccharides. Further, the prebiotic potential was evaluated by in vitro fermentation experiments using as inocula human fecal samples from volunteers in which the short-chain fatty acids production, total bacteria growth, and the bifidobacteria numbers were quantified and compared to the results obtained with commercial fructooligosaccharides. The accumulation of short-chain fatty acids was similar for XOS1 and XOS2 (102.7 and 117.2 mM). An increase of 1.50 and 1.43 log cell number/mL-fold was observed for media containing XOS1 and XOS2, respectively. Results obtained confirm that the production and use of XOS derived from steam-exploded barley straw such as functional ingredient is an alternative for the valorization of its hemicelluloses fraction into the "biorefinery" context. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.