Xylo-oligosaccharides, from xylans

R 126 M. A. Kabel, H. A. Schols and A.G.J. Voragen, Identification of Structural Features of Various (O-Acetylated) Xylo-Oligosaccharides from Xylan-Rich Agricultural By-Products A Review , p. 108 R 127 P.T. Larsson, Interaction between Cellulose I and Hemicelluloses Studied by Spectral Fitting of CP/MAS C-NMR Spectra , p. 254 Vol. 867, 2004... 

Identification of Structural Features of Various (O-Acetylated) Xylo-Oligosaccharides from Xylan-Rich Agricultural By-Products ... 

In this publication the rese ch performed within the framework of the PhD-research concerning the characterisation of complex xylo-oligosaccharides from xylan rich by-products (2) is reviewed. The separation and structural features of differently substituted xylo-oligosaccharides obtained from hydrothermally treated wheat bran, brewery s spent grain, com cobs and Eucalyptus wood is described. 

Unlike starch or cellulose, BSG hemicellulose has a complex structure, which is still present, in part, on its autohydrolysis products. Oligosaccharides from BSG hydrolysis consist mainly of branched arabino-xylo-glucurono oligosaccharides that are not highly acetylated when compared to other xylans, such as from Eucalyptus wood (31). The action of several enzymatic activities including endo-l,4-P-xylanase P-xylosidase and accessory activities such as acetyl xylanesterase, a-glucuronidase, and a-arabino-furanosidase is therefore required for the complete hydrolysis of OCL to monosaccharides. 

The D-xylanases of rumen microbial origin are all of the endo type, and degrade D-xylan, arabinoxylan, hemicellulose B, and xylo-oligosaccharides of d.p. 2=3, mainly to X2 and D-xylose X2 remains unattacked. The D-xylanases were found38,42 to have a higher affinity for linear D-xylans than for the branched hemicelluloses, namely, arabinoxylan and a branched B fraction from Trifolium pratense (red clover). The presence of L-arabinose, D-galactose, and uronic acid substituents on the D-xylan backbone thus appears to inhibit the action of these D-xylanases. The D-xylan was not effectively hydrolyzed until the side-group substituents had mostly been removed, for example, by arabinofuranosidase action on arabinoxylan.44... 

Several xylo-oligosaccharides of d.p. 2-7 have been isolated from enzymic hydrolyzates of terrestrial-plant D-xylans, arabinoxylans, arabino-4-O-methylglucuronoxylans, and 4-O-methylglucuronoxylans by the action of endo-xylanases,5,6,38-40,42-44,47,181,215-217,222,228 236,247-250, 254,256,258-261 an(j have been shown to constitute a series of /3-D-(l — 4)-linked D-xylo-oligosaccharides. 

Structures of Xylo-oligosaccharides Isolated from Enzymic Hydrolyzates of Rhodymenia palmata D-Xylan... 

The gibberellic acid-induced biosynthesis and release of cell-wall degrading e/jrfo-D-xylanase by isolated aleurone layers of barley have been studied. Studies on the D-xylanase system of Streptomyces species have included a study of the action of the enzyme on various o-xylans and D-xylo-oligosaccharides. The isolation and structural identification of arabino-D-xylo-oligosaccharides arising from action of the enzyme on corn cob arabino-D-xylan were reported. Mutant strains of Trichoderma viride not producing D-xylanase have been induced and isolated with the aid of nystatin selection. ... 

The main products resulting from the depolymerisation of the xylans during hydrothermal treatment are xylose and xylo-oligosaccharides (XOS) (3,4). Depending on the source of the by-product various (amounts of) substituents are linked to the xylans present (5). 

The precise location of the 0-acetyl substituents within the (arabino-)xylo-oligosaccharides has not been established yet. To our knowledge only few publications reported the presence of O-acetyl substituents in xylans from grasses (38,39) and is it for the first time that O-acetyl substituents are presented to occur in xylan-fragments obtained from cereals. A reason to explain the fact that the O-acetyl substituents are overseen in general can be that studies regarding the structural features of xylans normally include alkali-extractions to... 

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