Xylans from Oat Spelts and Birch Kraft Pulp

Abstract

Two different approaches for the isolation of xylan from hemicelluloserich sources have been investigated: Alkaline extraction from roller-mill pretreated oat spelts and Nitren extraction of birch kraft pulp. For xylan recovery from oat spelts the experiments included extraction with 5% NaOH at 90 8C, followed by precipitation in methanol or 2-propanol without neutralisation in order to facilitate NaOH recovery. A subsequent peroxide bleaching yielded a product of approximately 90% ISO brightness. The work on Nitren extraction of birch kraft pulp included the optimisation of the extraction process with regard to the Nitren charge. Nitren was much more specific in xylan extraction compared to Cuen, and up to 90% of the xylan content of the birch kraft pulp could be removed. It turned out that dried pulps were superior for this process compared to never-dried pulps, since substantial cellulose proportions in never-dried pulps were also mobilised by Nitren treatment. The properties of the recovered xylans from both processes were compared with regard to molar mass and substitution. It could be demonstrated that more or less intact arabinoxylans with molar masses of 30,000 g/mol could be obtained from oat spelts. The arabinoxylans contained 8-10 mol-% arabinofuranose and 2 mol-% 4-O-methylglucuronic acid substituents. Nitren extraction of a birch kraft pulp yielded xylans of 9,400 and 11,200 g/mol. Only traces of 4-O-methyl-glucuronic-and hexenuronic acid substituents could be found.

The effect of barley husk arabinoxylan adsorption on the properties of cellulose fibres

“…However, residues from agriculture represent a low cost source of xylan containing material that could be turned into an industrial opportunity if it is processed into value adding products (cf. van Wyk 2001;Puls et al 2006), where barley husks have been shown great potential (Glasser et al 2000;Höije et al 2005). The structure of barley husk xylan was early identified (Aspinall and Ferrier 1957) and is now fully characterized by means of NMR (Höije et al 2006).…”

Xyn10A, a Thermostable Endoxylanase from Acidothermus cellulolyticus 11B

“…The differences in the pattern of degradation products from the two xylans likely reflect the known differences in the structures of these xylans (13,17). Oat spelt xylan consists of arabinoxylan with trace glucose substituents, while birchwood xylan is primarily an unsubstituted xylose polymer with traces of uronic acids as side groups (17,22,30).…”

Carboxymethyl Xylan ‐ Control of Properties by Synthesis

“…[1][2][3][4] To get information about the reactivity of different xylans, the carboxymethylation under comparable conditions was investigated. Table 1 shows the results of the heterogeneous reaction and the carboxymethylation starting with the dissolved polymer of xylans from different sources.…”

“…Mostly the completely heterogeneous conversion yields higher DS values. Figure 6 shows 1 H NMR spectra of CMX of different xylans after chain degradation with 25% D 2 SO 4 . The signals for the protons of the CM substituents in position 2 and 3 can be identified.…”

“…[1,2] A new extraction method to isolate xylan from paper pulp uses the complex compound [Ni(tris(2-aminoethyl)amine)(OH) 2 ] (Nitren) in aqueous solution. [3,4] Carboxymethylation of polysaccharides is one of the most versatile functionalization procedures as it provides access to biobased materials with valuable properties like metal ion induced gel forming well studied for cellulose and starch. [5,6] Up to now, only a few papers describe carboxymethyl xylan (CMX) using AGX from corn cob, AX from oats and rice, and GX from beech wood with a degree of substitution (DS) lower than 1.…”