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Abstract: Streptomyces sp. SK519 was cultivated in the medium containing 0.5% birch wood xylan to produce extracellular xylanase. The xylanase was isolated from the culture supernatant by ammonium sulfate precipitation and partially purified by absorbing on the insoluble xylan. Alkali-extracted kenaf glucuronoylan of which main chain primarily consisting of (1-4)-linked β-D-xylopyranose (Xylp), some of which carry α-(1-2)-linked 4-O-methylglucopyranosyl acid (MeGlcAp) and glucopyranosyluronic acid (GlcAp) as side chain was digested with the xylanase preparation. At the final stage of digestion, main neutral oligosaccharides were xylotriose (Xyl3) and xylobiose (Xyl2) followed by xylotetraose (Xyl4). Xylose was only formed in a trace amount. As acidic oligosaccharides liberated, following seven aldopentao- and aldotetraouronic acids were isolated in a pure state, respectively, by preparative anion-exchange chromatography. Their structures were determined by analysis of constitutional sugar residues and 1H and 13C NMR spectroscopy. Xyl-β-1,4-[MeGlcA-α-1,2-]Xyl-β-1,4-Xyl-β-1,4-Xyl; [MeGlcA-α-1,2-]Xyl-β-1,4-Xyl-β-1,4-Xyl-β-1,4-Xyl; Xyl-β-1,4-[GlcA-α-1,2-]Xyl-β-1,4-Xyl-β-1,4-Xyl [GlcA-α-1,2-]Xyl-β-1,4-Xyl-β-1,4-Xyl-β-1,4-Xyl [MeGlcA-α-1,2-]Xyl-β-1,4-Xyl-β-1,4-D-Xyl [GlcA-α-1,2-]Xyl-β-1,4-Xyl-β-1,4-Xyl Xyl-β-1,4-Xyl-β-1,3-Rha-α-1,2-GalA-α-1,4-Xyl [Copyright &y& Elsevier]

Abstract: Methylation and partial acid hydrolysis of xylans from the bast and core of kenaf (Hibiscus cannabinus) showed that the main chain of these xylans consists of (1→4)-linked β-d-xylopyranosyl (Xylp) residues, some of which carry a α-1,2-linked 4-O-methyl-glucopyranosyluronic acid (Me-GlcAp) and glucopyranosyluronic acid (GlcAp) residues as side chains. Partial hydrolysis of kenaf xylans afforded two series of aldouronic acids from aldobio- to aldotetraouronic acids. The acids of the first series composed of 4-O-Me-d-GlcAp and d-Xylp residues: 4-O-Me-GlcA-Xyl3, 4-O-Me-GlcA-Xyl2 and 4-O-Me-GlcA-Xyl. The second series composed of d-GlcAp and d-Xylp: GlcA-Xyl3, GlcA-Xyl2 and GlcA-Xyl. In addition to these acids, another aldobiouronic acid, 4-O-(α-d-GalAp)-d-Xyl was found to be present in the partial hydrolysate. The molar ratio of GalA, GlcA, 4-O-Me-GlcA, and Xyl residues was calculated to be 1.0:2.0:9.4:119 for the bast xylan and 1.0:1.3:7.9:99.4 for the core xylan. [Copyright &y& Elsevier]