title: Enzymatic fractionation of SAA-pretreated barley straw for production of fuel ethanol and astaxanthin as a value-added co-product.
abstract: 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.
authors.affiliation: Sustainable Biofuels and Co-Products Research Unit, Eastern Regional Research Center, Agricultural Research Service, USDA, Wyndmoor, PA 19038, USA. John.nghiem@ars.usda.gov
authors.forename: Nhuan P
authors.initials: NP
authors.lastname: Nghiem
authors.forename: Tae Hyun
authors.initials: TH
authors.lastname: Kim
authors.forename: Chang Geun
authors.initials: CG
authors.lastname: Yoo
authors.forename: Kevin B
authors.initials: KB
authors.lastname: Hicks
mesh_terms: D000641:Ammonia / Q000737:chemistry*; D001487:Basidiomycota / Q000378:metabolism; D056804:Biofuels; D002482:Cellulose / Q000378:metabolism; D000431:Ethanol / Q000737:chemistry*; D005285:Fermentation; D006026:Glycoside Hydrolases / Q000378:metabolism*; D001467:Hordeum / Q000737:chemistry*; D006868:Hydrolysis; D007101:Immersion; D008031:Lignin / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D014867:Water / Q000737:chemistry; D024341:Xanthophylls / Q000096:biosynthesis / Q000737:chemistry; D014994:Xylose / Q000737:chemistry
chemical_list: D056804:Biofuels; D024341:Xanthophylls; D014867:Water; C036909:lignocellulose; D000431:Ethanol; D000641:Ammonia; C005948:astaxanthine; D002482:Cellulose; D008031:Lignin; D014994:Xylose; D006026:Glycoside Hydrolases; C023305:hemicellulase