title: Metabolic engineering of Clostridium acetobutylicum for the enhanced production of isopropanol-butanol-ethanol fuel mixture.
abstract: Butanol is considered as a superior biofuel, which is conventionally produced by clostridial acetone-butanol-ethanol (ABE) fermentation. Among ABE, only butanol and ethanol can be used as fuel alternatives. Coproduction of acetone thus causes lower yield of fuel alcohols. Thus, this study aimed at developing an improved Clostridium acetobutylicum strain possessing enhanced fuel alcohol production capability. For this, we previously developed a hyper ABE producing BKM19 strain was further engineered to convert acetone into isopropanol. The BKM19 strain was transformed with the plasmid pIPA100 containing the sadh (primary/secondary alcohol dehydrogenase) and hydG (putative electron transfer protein) genes from the Clostridium beijerinckii NRRL B593 cloned under the control of the thiolase promoter. The resulting BKM19 (pIPA100) strain produced 27.9 g/l isopropanol-butanol-ethanol (IBE) as a fuel alcohols with negligible amount of acetone (0.4 g/l) from 97.8 g/l glucose in lab-scale (2 l) batch fermentation. Thus, this metabolically engineered strain was able to produce 99% of total solvent produced as fuel alcohols. The scalability and stability of BKM19 (pIPA100) were evaluated at 200 l pilot-scale fermentation, which showed that the fuel alcohol yield could be improved to 0.37 g/g as compared to 0.29 g/g obtained at lab-scale fermentation, while attaining a similar titer. To the best of our knowledge, this is the highest titer of IBE achieved and the first report on the large scale fermentation of C. acetobutylicum for IBE production.
authors.affiliation: Dept. of Chemical and Biomolecular Engineering (BK21 Program), Metabolic and Biomolecular Engineering National Research Laboratory, BioProcess Engineering Research Center, KAIST, Daejeon, 305-701, Republic of Korea.
authors.forename: Yu-Sin
authors.initials: YS
authors.lastname: Jang
authors.forename: Alok
authors.initials: A
authors.lastname: Malaviya
authors.forename: Joungmin
authors.initials: J
authors.lastname: Lee
authors.forename: Jung Ae
authors.initials: JA
authors.lastname: Im
authors.forename: Sang Yup
authors.initials: SY
authors.lastname: Lee
authors.forename: Julia
authors.initials: J
authors.lastname: Lee
authors.forename: Moon-Ho
authors.initials: MH
authors.lastname: Eom
authors.forename: Jung-Hee
authors.initials: JH
authors.lastname: Cho
authors.forename: Do Young
authors.initials: do Y
authors.lastname: Seung
mesh_terms: D019840:2-Propanol / Q000378:metabolism*; D056804:Biofuels; D000440:Butanols / Q000378:metabolism*; D046969:Clostridium acetobutylicum / Q000378:metabolism*; D000431:Ethanol / Q000378:metabolism*; D060847:Metabolic Engineering
chemical_list: D056804:Biofuels; D000440:Butanols; D000431:Ethanol; D019840:2-Propanol
keywords: Clostridium acetobutylicum; IBE; butanol; isopropanol; pilot-scale