Whistler, Xylan

Mary L. Caldwell and Mildred Adams, Action of Certain Alpha Amylases.. 229 Roy L. Whistler, Xylan. 269... 

This result could not have been achieved by acid hydrolysis, which would have attacked the furanosidic residues first. Whistler and Masak studied the action of an enz3une preparation from Aspergillm foetidus on corn-cob xylan and found that the effect depended very largely on the way in which the enzyme had been purified. 

Whistler has reviewed the behavior of xylan on acetylation, and notes that dry xylan is acetylated with difficulty. Under reaction conditions which avoid drying, xylan is acetylated readily, to yield a diacetate which is insoluble in most solvents. Because of its insolubility, xylan diacetate, especially if the D. P. is relatively high, can cause filtration difficulties and haziness in commercial cellulose acetates. 

Alkaline extraction of wood is usually carried out at or below room temperature for limited periods of time and in an atmosphere of nitrogen. Under these conditions, any changes in the xylan brought about by the alkali are kept at a minimum, excepting a complete de-O-acetylation. Whistler and Corbett found that a corncob xylan was stable in N sodium... 

Cellulose microfibrils are usually embedded in a continuous phase of lignin, pectin, and hemicellulose hemicellulose usually predominates (Whistler and Richards, 1970). Most of the hemicellulose is found mixed with cellulose in both the primary and secondary cell walls. Hemicellulose is now known not be a precursor to cellulose. In general, hemicellu-loses are the cell wall polysaccharides other than cellulose and pectin. These polymers are classified on the basis of the type of sugar residues present. For example, o-xylan is made up of D-xylose, D-mannan of D-mannose, and D-galactan of D-galactose units (Whistler and Richards, 1970). In practice, few hemicelluloses contain only one sugar, most contain two to four. Furthermore most hemicelluloses have branched structures. The major types of hemicellulose and their distribution have been reviewed (Whistler and Richards, 1970). Methods for the analysis of mannans have been reviewed (Matheson, 1990). 

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