Xylans, acetates hydrolysis

Kong, F., Engler, C. R., and Soltes, E. J., Effects of cell-wall acetate, xylan backbone, and lignin on enzymatic hydrolysis of aspen wood. Appl Biochem Biotechnol 1993, 34/35, 23-35. 

It is apparent from the foregoing that a more specific method for the determination of xylan would be desirable. To this end, the determination of xylose, after acid hydrolysis of the polysaccharide material, has been attempted. Xylose may be oxidized to xylonic acid which can be precipitated with cadmium bromide as the double salt, but the precipitation is not quantitative. Xylose forms an insoluble, crystalline di-O-benzylidene dimethyl acetal which permits identification in the presence of other sugars, but the necessity for anhydrous reaction conditions precludes the adaptation of this method to ordinary analysis. AVise and Ratliff prepared this derivative of both d- and L-xylose, as well as analogous derivatives from other aromatic aldehydes, and concluded that, with either the di-O-benzylidene or the di-O-(p-isopropylbenzylidene) dimethyl acetal, an excellent, highly specific, qualitative test was available for d- or n-xylose. 

Quantitative acid hydrolysis with 72% (w/w) H2SO4 [19] was used to characterize the BSG feedstock. The monosaccharides and acetic acid were determined by HPLC to estimate (after corrections for stoichiometry and sugar decomposition) the contents of glucan (cellulose) and hemicelluloses (xylan, arabinan, and acetyl groups) in the sample. The acid-insoluble residue after hydrolysis was recovered by filtration and considered as Klason lignin after correction for the acid-insoluble ash. Protein was determined by the KJeldahl method [20] using the Ax 6.25 conversion factor. 

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