title: Metabolic process engineering of Clostridium tyrobutyricum Δack-adhE2 for enhanced n-butanol production from glucose: effects of methyl viologen on NADH availability, flux distribution, and fermentation kinetics.
abstract: Butanol biosynthesis through aldehyde/alcohol dehydrogenase (adhE2) is usually limited by NADH availability, resulting in low butanol titer, yield, and productivity. To alleviate this limitation and improve n-butanol production by Clostridium tyrobutyricum Δack-adhE2 overexpressing adhE2, the NADH availability was increased by using methyl viologen (MV) as an artificial electron carrier to divert electrons from ferredoxin normally used for H2 production. In the batch fermentation with the addition of 500 μM MV, H2 , acetate, and butyrate production was reduced by more than 80-90%, while butanol production increased more than 40% to 14.5 g/L. Metabolic flux analysis revealed that butanol production increased in the fermentation with MV because of increased NADH availability as a result of reduced H2 production. Furthermore, continuous butanol production of ∼55 g/L with a high yield of ∼0.33 g/g glucose and extremely low ethanol, acetate, and butyrate production was obtained in fed-batch fermentation with gas stripping for in situ butanol recovery. This study demonstrated a stable and reliable process for high-yield and high-titer n-butanol production by metabolically engineered C. tyrobutyricum by applying MV as an electron carrier to increase butanol biosynthesis.
authors.affiliation: William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, 140 West 19th Avenue, Columbus, Ohio, 43210.
authors.forename: Yinming
authors.initials: Y
authors.lastname: Du
authors.forename: Wenyan
authors.initials: W
authors.lastname: Jiang
authors.forename: Mingrui
authors.initials: M
authors.lastname: Yu
authors.forename: I-Ching
authors.initials: IC
authors.lastname: Tang
authors.forename: Shang-Tian
authors.initials: ST
authors.lastname: Yang
mesh_terms: D020001:1-Butanol / Q000378:metabolism*; D000085:Acetates / Q000378:metabolism; D001709:Biotechnology / Q000379:methods; D002087:Butyrates / Q000378:metabolism; D048014:Clostridium tyrobutyricum / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D005285:Fermentation; D015870:Gene Expression; D005947:Glucose / Q000378:metabolism*; D006859:Hydrogen / Q000378:metabolism; D060847:Metabolic Engineering; D064688:Metabolic Flux Analysis; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D009243:NAD / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D010269:Paraquat / Q000378:metabolism
chemical_list: D000085:Acetates; D002087:Butyrates; D009243:NAD; D006859:Hydrogen; D020001:1-Butanol; D010088:Oxidoreductases; D005947:Glucose; D010269:Paraquat
keywords: Clostridium tyrobutyricum; artificial electron carrier; metabolic flux analysis; methyl viologen; n-butanol