title: Conversion of switchgrass to ethanol using dilute ammonium hydroxide pretreatment: influence of ecotype and harvest maturity.
abstract: Switchgrass (Panicum virgatum L.) is a perennial C4 grass that is being developed as a bioenergy crop because it has high production yields and suitable agronomic traits. Five switchgrass biomass samples from upland and lowland switchgrass ecotypes harvested at different stages or maturity were used in this study. Switchgrass samples contained 317.0-385.0 g glucans/kg switchgrass dry basis (db) and 579.3-660.2 g total structural carbohydrates/kg switchgrass, db. Carbohydrate contents were greater for the upland ecotype versus lowland ecotype and increased with harvest maturity. Pretreatment of switchgrass with dilute ammonium hydroxide (8% w/w ammonium loading) at 170 degrees C for 20 min was determined to be effective for preparing switchgrass for enzymatic conversion to monosaccharides; glucose recoveries were 66.9-90.5% and xylose recoveries 60.1-84.2% of maximum and decreased with increased maturity at harvest. Subsequently, pretreated switchgrass samples were converted to ethanol by simultaneous saccharification and fermentation using engineered xylose-fermenting Saccharomyces cerevisiae strain YRH400. Ethanol yields were 176.2-202.01/Mg of switchgrass (db) and followed a similar trend as observed for enzymatic sugar yields.
authors.affiliation: Bioenergy Research Unit, National Center for Agricultural Utilization Research, USDA, Agricultural Research Service, 1815 N. University Street, Peoria, IL 61604-3902, USA. bruce.dien@ars.usda.gov
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Dien
authors.affiliation: Bioenergy Research Unit, National Center for Agricultural Utilization Research, USDA, Agricultural Research Service, 1815 N. University Street, Peoria, IL 61604-3902, USA.
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: O'Bryan
authors.affiliation: Bioenergy Research Unit, National Center for Agricultural Utilization Research, USDA, Agricultural Research Service, 1815 N. University Street, Peoria, IL 61604-3902, USA.
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Hector
authors.affiliation: Bioenergy Research Unit, National Center for Agricultural Utilization Research, USDA, Agricultural Research Service, 1815 N. University Street, Peoria, IL 61604-3902, USA.
authors.forename: Loren B
authors.initials: LB
authors.lastname: Iten
authors.affiliation: Grain, Forage, and Bioenergy Research Unit, University of Nebraska, 137 Keim Hall, Box 830937, Lincoln, NE 68583-0937, USA.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Mitchell
authors.affiliation: Bioenergy Research Unit, National Center for Agricultural Utilization Research, USDA, Agricultural Research Service, 1815 N. University Street, Peoria, IL 61604-3902, USA.
authors.forename: Nasib
authors.initials: N
authors.lastname: Qureshi
authors.affiliation: Grain, Forage, and Bioenergy Research Unit, University of Nebraska, 137 Keim Hall, Box 830937, Lincoln, NE 68583-0937, USA.
authors.forename: Gautum
authors.initials: G
authors.lastname: Sarath
authors.affiliation: Grain, Forage, and Bioenergy Research Unit, University of Nebraska, 137 Keim Hall, Box 830937, Lincoln, NE 68583-0937, USA.
authors.forename: Kenneth P
authors.initials: KP
authors.lastname: Vogel
authors.affiliation: Bioenergy Research Unit, National Center for Agricultural Utilization Research, USDA, Agricultural Research Service, 1815 N. University Street, Peoria, IL 61604-3902, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Cotta
mesh_terms: D064753:Ammonium Hydroxide / Q000737:chemistry*; D056804:Biofuels; D018533:Biomass; D001709:Biotechnology; D000431:Ethanol / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D005285:Fermentation; D005947:Glucose / Q000032:analysis / Q000378:metabolism; D008897:Panicum / Q000737:chemistry* / Q000378:metabolism*; D014994:Xylose / Q000032:analysis / Q000378:metabolism
chemical_list: D056804:Biofuels; D000431:Ethanol; D064753:Ammonium Hydroxide; D014994:Xylose; D005947:Glucose