Complex xylo-oligosaccharides identified from hydrothermally treated Eucalyptus wood and breweryʹs spent grain

Hydrolysates from two hydrothermally treated xylan-rich agrobased materials, Eucalyptus wood and breweryʹs spent grain were fractionated by anion-exchange chromatography and size-exclusion chromatography. Hereby, several pools were obtained and they were characterised by their sugar composition. Additionally, the oligosaccharides in the pools described were further identified by high-performance anion-exchange chromatography and mass spectrometry. The hydrothermally treated breweryʹs spent grain resulted in three pools of which two contained relatively high molecular weight xylan, singly and doubly branched with arabinose [XnAm], separated from a pool of xylo-oligosaccharides less branched with arabinose. The fractionation of the hydrothermally treated Eucalyptus wood resulted in a neutral pool, mainly consisting of a series of (acetylated) xylo-oligosaccharides [XnAcm], and three acidic pools. Two of these acidic pools contained a series of (acetylated) xylo-oligosaccharides including one 4-O-methylglucuronic acid [Xn(GlcAme)1Acm], while the third acidic pool contained (acetylated) xylo-oligosaccharides substituted with two 4-O-methylglucuronic acids [Xn(GlcAme)2Acm]. Additionally, a series of xylo-oligosaccharides containing both 4-O-methylglucuronic acid and a hexose, most likely galactose, was detected in the acidic Eucalyptus pools [Xn(GlcAme)1 or 2AcmH]. Information was obtained about the number of acetyl-groups linked to the (4-O-methylglucurono-) xylo-oligosaccharides. Finally, it is demonstrated with an example that the different substituents to the xylo-oligosaccharides present are of relevance for the fermentability of the xylo-oligosaccharides by human faecal samples.