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Nghiem N.P.,Sustainable Biofuels and Co Products Research Unit | Kim T.H.,Kongju National University | Yoo C.G.,Iowa State University | Hicks K.B.,Sustainable Biofuels and Co Products Research Unit
Applied Biochemistry and Biotechnology

Barley straw was used to demonstrate an integrated process for production of fuel ethanol and astaxanthin as a value-added co-product. Barley straw was pretreated by soaking in aqueous ammonia using the previously determined optimum conditions, which included 77.6 C treatment temperature, 12.1 h treatment time, 15 wt% ammonia concentration, and 1:8 solid-to-liquid ratio. In the newly developed process, the pretreated barley straw was first hydrolyzed with ACCELLERASE® XY (a commercial hemicellulase product) to generate a xylose-rich solution, which contained 3.8 g/l glucose, 22.9 g/l xylose, and 2.4 g/l arabinose, with 96 % of the original glucan being left intact. The xylose-rich solution was used for production of astaxanthin by the yeast Phaffia rhodozyma without further treatment. The resulting cellulose-enriched solid residue was used for ethanol production in a fed-batch simultaneous saccharification and fermentation using ACCELLERASE® 1500 (a commercial cellulase product) and the industrial yeast Saccharomyces cerevisiae. At the end of the fermentation, 70 g/l ethanol was obtained, which was equivalent to 63 % theoretical yield based on the glucan content of the solid substrate. © 2013 Springer Science+Business Media New York (outside the USA). Source

Yadav M.P.,Sustainable Biofuels and Co Products Research Unit | Hicks K.B.,Sustainable Biofuels and Co Products Research Unit
Carbohydrate Polymers

Both barley hulls and straw contain valuable arabinoxylans and other useful carbohydrate and non-carbohydrate components. The functional water soluble non-caloric arabinoxylan (hemicellulose B) fraction was isolated from hot water-extracted and de-starched barley hulls and straws by an alkaline hydrogen peroxide extraction followed by ethanol precipitation. Barley hulls contained comparatively more Hemi. B (20.51%) than barley straws (7.41 to 12.94%). The sugar composition of Hemi. B showed that they were typical arabinoxylans containing (in addition to arabinose and xylose) some galactose, glucose and acidic sugars in the side chains. The hemicellulose B fractions from barley straws were superior oil-in-water emulsifiers than those from barley hulls. These Hemi. B fractions contain protein, which contributes to their emulsions stabilizing property. © Published by Elsevier Ltd. Source

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