title: Aqueous ammonia soaking of switchgrass followed by simultaneous saccharification and fermentation.
abstract: Simultaneous saccharification and fermentation (SSF) of switchgrass was performed following aqueous ammonia pretreatment. Switchgrass was soaked in aqueous ammonium hydroxide (30%) with different liquid-solid ratios (5 and 10 ml/g) for either 5 or 10 days. The pretreatment was carried out at atmospheric conditions without agitation. A 40-50% delignification (Klason lignin basis) was achieved, whereas cellulose content remained unchanged and hemicellulose content decreased by approximately 50%. The Sacccharomyces cerevisiae (D5A)-mediated SSF of ammonia-treated switchgrass was investigated at two glucan loadings (3 and 6%) and three enzyme loadings (26, 38.5, and 77 FPU/g cellulose), using Spezyme CP. The percentage of maximum theoretical ethanol yield achieved was 72. Liquid-solid ratio and steeping time affected lignin removal slightly, but did not cause a significant change in overall ethanol conversion yields at sufficiently high enzyme loadings. These results suggest that ammonia steeping may be an effective method of pretreatment for lignocellulosic feedstocks.
authors.affiliation: Department of Agricultural and Biosystems Engineering, Iowa State University, Ames, IA 50011, USA. isci@iastate.edu
authors.forename: Asli
authors.initials: A
authors.lastname: Isci
authors.forename: Jennifer N
authors.initials: JN
authors.lastname: Himmelsbach
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Pometto
authors.forename: D Raj
authors.initials: DR
authors.lastname: Raman
authors.forename: Robert P
authors.initials: RP
authors.lastname: Anex
mesh_terms: D064753:Ammonium Hydroxide; D000821:Animal Feed / Q000032:analysis; D019149:Bioreactors; D001709:Biotechnology; D002482:Cellulose / Q000378:metabolism; D000431:Ethanol / Q000378:metabolism; D005285:Fermentation; D006878:Hydroxides; D008031:Lignin / Q000378:metabolism; D008897:Panicum / Q000737:chemistry* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D014867:Water
chemical_list: D006878:Hydroxides; D014867:Water; C036909:lignocellulose; D000431:Ethanol; D064753:Ammonium Hydroxide; D002482:Cellulose; D008031:Lignin