Xylose oligomers from xylan during pretreatment
by Carrier, D.; Lau, C.; Bunnell, K.; Clausen, E.; Lay, J.; Gideon, J.
In addn. to cellulose and lignin, hemicellulose makes up to 30% of biomass. With different compns. in different plant genus, hemicellulose is generally a polymer composed of xylose residues that are linked by ß-(1-4) glycosidic bonds to which other sugars, such as arabinose and glucose, are attached. To release hemicellulose from biomass as sugar for fermn., pretreatment is mandatory. The efficacy of pretreatment is rated according to the prodn. of a reactive hemicellulose fraction that can readily undergo fermn. to produce ethanol. Unfortunately, hemicellulose oligomers do not depolymerize directly into xylose, but form oligomers of various lengths, which can, in turn, form furfural and acetic acid; both are inhibitors of the fermn. process. Understanding hemicellulose depolymn. is important because it impacts, through the formation of fermn. inhibitors, the overall conversion process by lowering the ethanol prodn. yields. The presentation will conc. on birchwood xylan, a type of hemicelluloses that contains 97% of sugars in the polysaccharide form of xylose. The material was hydrolyzed in 1% sulfuric acid at 130C to produce xylose oligomers. The identity of each xylose oligomer fraction was confirmed with the spiking of std. oligomers in HPLC expts. and verified by the mol. wt. via MALDI anal. The presentation will show results of the fractionation by centrifugal partition chromatog. of the individual oligomer fragments, as well as their tracking throughout the depolymn. process.