TECHNOLOGY FOCUS - BIOLOGY - Preferred Method: The released sugars, preferably 5C-sugars are transferred using an oxidoreductase in a lactone, especially a gamma -lactone, and hydrolyzed to the corresponding carboxylic acid, by enzymatic and/or non-enzymatic spontaneous hydrolysis. The obtained carboxylic acid is dehydrated, using a keto-acid dehydratase. The keto-acid is dehydrated to a ketocarboxylic acid semialdehyde using a dehydratase. The keto-acid semialdehyde is oxidized to a dicarboxylic acid using an oxidoreductase. The reduction of at least one oxidoreductase redox cofactor NADH and/or NADPH is/are converted to the oxidized state of NAD+ and/or NADP+ in the same reaction batch using at least one further oxidoreductase, preferably a xylose reductase, a lactate dehydrogenase, an oxidase or at least one redox enzyme, which is coupled to an electrode. The resulting compounds having an ionic bond are separated from the reaction mixture using ion exchange chromatography and/or electrodialysis. The hemicellulose-containing material is obtained from lignocellulosic material, by treating lignocellulosic material with an alkaline, aqueous alcohol solution, at 50-100 degrees C. The lignocellulose-containing material is derived from lignocellulosic biomass comprising straw, bagasse (both preferred), annual plants, energy grass, sisal, or atypical lignocellulosic substrates, such as husks. Preferred Components: The sugars are arabinose and/or xylose, preferably L-arabinose and/or D-xylose. The sugar is arabinose. The lactone is arabino- gamma -lactone. The carboxylic acid is arabonic acid. The keto-acid is 2-keto-3-deoxyarabonic acid. The ketocarboxylic acid semialdehyde is alpha -ketoglutaric acid semialdehyde. The dicarboxylic acid is alpha -ketoglutaric acid. EXAMPLE - 8 wt/vol.% Xylan was suspended in acetate buffer with pH 4.3 and mixed with Accellerase TRIO Genencor (RTM: Commercial enzyme containing multiple glycolytic activities including exo-1,4- beta -glucanase, endo-1,4- beta -glucanase, hemicellulase and beta -glucosidase) at 1 g/1 g of xylan. The mixture was stirred for 24 hours at 50 degrees C. The pH was checked and adjusted in case of discrepancy over 4.5 or below 4.1. The mixture was filtered through a Buchner funnel, and the filtrate (the hydrolyzate) was analyzed for its composition of monomers, and its concentration. The filtrate contained a concentration of 6% xylose, 0.43% arabinose and 0.27% glucose. About 85% of xylose in xylan was thus obtained in monomeric form.