Characterisation of complex xylo-oligosaccharides from xylan rich by-products
2002
Kabel, M.A.
Hydrolysates obtained by hydrothermal treatment of four xylan rich by-products (wheat bran, brewery's spent grain, corn cobs and Eucalyptus wood) were characterised. Depending on the feedstock material studied, the xylan originally present differed in substitution with arabinose, 4- O -methylglucuronic acid and O -acetyl substituents. Due to a partial release of the various substituents and depolymerisation of the xylan by the hydrothermal treatments performed, a wide variety of differently substituted XOS and xylan-fragments were obtained.High performance anion-exchange chromatography (HPAEC), reversed phase (RP)-high performance liquid chromatography (HPLC), mass spectrometry (MS), NMR spectroscopy, RP-HPLC-MS and RP-HPLC-NMR showed to be very useful for the separation and characterisation of the detailed structures of the substituted XOS.The differently substituted XOS in the hydrolysates of brewery's spent grain and Eucalyptus wood were separated by anion-exchange and size-exclusion chromatography and characterised in more detail. The XOS in the brewery's spent grain hydrolysate included mainly xylan-fragments substituted with arabinoses and XOS containing only few substituents. Furthermore, arabinoxylan-fragments having O -acetyl substitution were present, suggesting the presence of O -acetyl in cereal arabinoxylans. The Eucalyptus wood hydrolysate contained mainly linear XOS, O -acetylated XOS and ( O -acetylated) XOS substituted with one or two 4- O -methylglucuronic acid(s). Additionally, a series of XOS containing both 4- O -methyl-glucuronic acid and a hexose, most likely galactose, was identified.
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