title: Effect of nitric acid on pretreatment and fermentation for enhancing ethanol production of rice straw.
abstract: In this study, nitric acid (HNO₃) was evaluated as an acid catalyst for rice straw pretreatment, and, after neutralization, as a sole nitrogen source for subsequent fermentation. Response surface methodology was used to obtain optimal pretreatment condition with respect to HNO₃ concentration (0.2-1.0%), temperature (120-160 °C) and reaction time (1-20 min). In a condition of 0.65% HNO₃, 158.8 °C and 5.86 min, a maximum xylose yield of 86.5% and an enzymatic digestibility of 83.0% were achieved. The sugar solution that contained nitrate derived from the acid catalyst supported the enhancement of ethanol yield by Pichia stipitis from 10.92 g/L to 14.50 g/L. The results clearly reveal that nitric acid could be used not only as a pretreatment catalyst, but also as a nitrogen source in the fermentation process for bioethanol production. It is anticipated that the HNO₃-based pretreatment can reduce financial burden on the cellulosic bioethanol industry by simplifying after-pretreatment-steps as well as providing a nitrogen source.
authors.affiliation: Department of Civil and Environmental Engineering, KAIST, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Republic of Korea.
authors.forename: Ilgook
authors.initials: I
authors.lastname: Kim
authors.forename: Bomi
authors.initials: B
authors.lastname: Lee
authors.forename: Ji-Yeon
authors.initials: JY
authors.lastname: Park
authors.forename: Sun-A
authors.initials: SA
authors.lastname: Choi
authors.forename: Jong-In
authors.initials: JI
authors.lastname: Han
mesh_terms: D002384:Catalysis; D000431:Ethanol / Q000378:metabolism*; D005163:Factor Analysis, Statistical; D005285:Fermentation; D006868:Hydrolysis; D008031:Lignin / Q000378:metabolism; D017942:Nitric Acid / Q000737:chemistry* / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D012275:Oryza / Q000737:chemistry*; D010843:Pichia / Q000378:metabolism*; D018547:Plant Stems / Q000737:chemistry*; D014866:Waste Products; D014994:Xylose / Q000096:biosynthesis
chemical_list: D014866:Waste Products; D000431:Ethanol; D017942:Nitric Acid; D008031:Lignin; D014994:Xylose; D009584:Nitrogen
keywords: Enzymatic hydrolysis; Fermentation; HNO(3) pretreatment; RSM; Rice straw