Xylans composition

C/H, cellulose/hemicellulose composition ratio G/X, glucan/xylan composition ratio AX/AG, xylan/glucan degradation ratio (this ratio was calculated assuming little change in the sum of ash, lignin, and extractives). 

Saxena, A., Elder, T.J., Ragauskas, A.J. Moisture barrier properties of xylan composite films. Carbohydr. Polym. 84, 1371-1377 (2011)... 

The aim of this chapter is to summarize some of the research findings on xylan, a natural polymer extracted from corn cobs, which presents a promising application in the development of colon-specific drug carriers. Physicochemical characterization of the polymer regarding particle size and morphology, composition, rheology, thermal behavior, and crystallinity will be provided. Additionally, research data on its extraction and the development of microparticles based on xylan and prepared by different methods will also be presented and discussed. 

Since the terms xylan, pentosan, hemicellulose and hemicellulose-A often refer to the same substance or to substances which differ only slightly, the literature is sometimes confusing. In this review the term xylan will be used to signify preparations which are believed to be reasonably pure, the term pentosan will be used to designate material the composition of which is based on furfural estimation, and the term hemicellulose will be used to denote polysaccharide preparations of uncertain composition. 

Usually it is considered that xylan has been effectively removed if the extracted residue compares in composition to a-cellulose. Yet, even a-cellulose contains small amounts of xylan as well as other hemicelluloses such as mannan.67 69 Beta and 7-cellulose are mixtures which contain pentosans along with other alkali-soluble extractives.1M0... 

The particular wood species we chose for this study is aspen (Populus tremuloides), which is plentiful in Canada and in the northern U.S.A. The chemical composition we found to be glucan 53.4%, xylan 14.9%, total carbohydrate 79.0%, lignin 17.1% and extractives 3.8%. We would expect total fermentable sugars of about 56% in this sample of aspen in anhydro form (Timell has reported about 60% in another sample (15)) which upon hydrolysis would yield about 1,250 lb wood sugars per ton of wood (dry basis), from the stoichiometry. Theoretical conversion of this sugar to ethanol would yield 640 lb or 81.1 gallons of anhydrous... 

A mixture of three newspapers issued in Korea was used as substrate. Newspaper was cut into approx 0.5 x 0.5 cm pieces. The moisture of the paper was 6.8 wt% with the following composition 56.2 wt% glucan, 13.9 wt% xylan + mannan + galactan (XMG), 15.0 wt% klason lignin, and 7.4 wt% ash. The nonionic surfactants (TCI Tokyo Kasei Kogyo, Tokyo, Japan) used are listed in Table 1. 

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