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

Abstract

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 productionof xylooligosaccharides (XOS) mixtures from soluble hemicelluloses by steam-explosionpretreatment. This fraction was treated by ion-exchange (XOS1) and a combination ofmembrane filtration, enzymatic hydrolysis, and ion-exchange processes (XOS2) to produceprebiotic compounds. The afforded products were then characterized by using analyticaltechniques, including HPAEC-PAD, FTIR, and MALDI-TOF-MS. XOS2 is composed of a back-bone of xylopyranosyl branched, which including acetyl-esterified oligosaccharides andferuloyl substituted arabino-oligosaccharides.Further, the prebiotic potential was evaluated by in vitro fermentation experiments usingas inocula human fecal samples from volunteers in which the short-chain fatty acidsproduction, total bacteria growth, and the bifidobacteria numbers were quantified and com-pared to the results obtained with commercial fructooligosaccharides.The accumulation of short-chain fatty acids was similar for XOS1 and XOS2 (102.7 and117.2 mM). An increase of 1.50 and 1.43 log cell number/mL-fold was observed for mediacontaining XOS1 and XOS2, respectively. Results obtained confirm that the production anduse of XOS derived from steam-exploded barley straw such as functional ingredient is analternative for the valorization of its hemicelluloses fraction into the “biorefinery” context.