title: Improved one-step steam pretreatment of SO2-impregnated softwood with time-dependent temperature profile for ethanol production.
abstract: In the production of ethanol from lignocellulosic material, pretreatment of the raw material before enzymatic hydrolysis and fermentation is essential to obtain high overall yields of sugar and ethanol. Two-step steam pretreatment results in higher ethanol yields from softwood than the standard one-step pretreatment process. However, the difficulty with separation and washing of the material at high pressure between the two pretreatment steps is a major drawback. In this study, a new one-step pretreatment procedure was investigated, in which the time-temperature profile was varied during pretreatment. The efficiency of pretreatment was assessed by performing simultaneous saccharification and fermentation on the pretreated slurries. Pretreatment of SO(2)-impregnated softwood performed by varying the temperature (190-226 degrees C), the residence time (5-10 min), and the mode of temperature increase (linear or stepwise), resulted in recovery of about 90% of the mannose and glucose present in the raw material. The highest ethanol yield, 75% of theoretical based on the glucan and mannan content of the raw material, was obtained at pretreatment conditions of 190 degrees C for 12 min. Similar ethanol yields were achieved when running the pretreatment as one-step (190-200 degrees C), two levels of temperature, at shorter residence time (7 min), which results in lower capital costs for the process.
authors: Department of Chemical Engineering, Lund University, Lund, Sweden. sanam.monavari@chemeng.lth.se
authors: Sanam
authors: S
authors: Monavari
authors: Andrea
authors: A
authors: Bennato
authors: Mats
authors: M
authors: Galbe
authors: Guido
authors: G
authors: Zacchi
mesh_terms: D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D008031:Lignin / Q000737:chemistry / Q000378:metabolism; D013227:Steam; D013458:Sulfur Dioxide / Q000737:chemistry*; D013696:Temperature
chemical_list: D013227:Steam; D013458:Sulfur Dioxide; C036909:lignocellulose; D000431:Ethanol; D008031:Lignin