title: Metabolic engineering of Clostridium acetobutylicum M5 for highly selective butanol production.
abstract: To improve butanol selectivity, Clostridium acetobutylicum M5(pIMP1E1AB) was constructed by adhE1-ctfAB complementation of C. acetobutylicum M5, a derivative strain of C. acetobutylicum ATCC 824, which does not produce solvents due to the lack of megaplasmid pSOL1. The gene products of adhE1-ctfAB catalyze the formation of acetoacetate and ethanol/butanol with acid re-assimilation in solventogenesis. Effects of the adhE1-ctfAB complementation of M5 were studied by batch fermentations under various pH and glucose concentrations, and by flux balance analysis using a genome-scale metabolic model for this organism. The metabolically engineered M5(pIMP1E1AB) strain was able to produce 154 mM butanol with 9.9 mM acetone at pH 5.5, resulting in a butanol selectivity (a molar ratio of butanol to total solvents) of 0.84, which is much higher than that (0.57 at pH 5.0 or 0.61 at pH 5.5) of the wild-type strain ATCC 824. Unlike for C. acetobutylicum ATCC 824, a higher level of acetate accumulation was observed during fermentation of the M5 strain complemented with adhE1 and/or ctfAB. A plausible reason for this phenomenon is that the cellular metabolism was shifted towards acetate production to compensate reduced ATP production during the largely growth-associated butanol formation by the M5(pIMP1E1AB) strain.
authors.affiliation: Metabolic and Biomolecular Engineering National Research Laboratory, Department of Chemical and Biomolecular Engineering (BK21 Program), BioProcess Engineering Research Center, Center for Systems and Synthetic Biotechnology, Institute for the BioCentury, KAIST, Daejeon 305-701, Republic of Korea.
authors.forename: Jin Young
authors.initials: JY
authors.lastname: Lee
authors.forename: Yu-Sin
authors.initials: YS
authors.lastname: Jang
authors.forename: Joungmin
authors.initials: J
authors.lastname: Lee
authors.forename: Eleftherios Terry
authors.initials: ET
authors.lastname: Papoutsakis
authors.forename: Sang Yup
authors.initials: SY
authors.lastname: Lee
mesh_terms: D000096:Acetone / Q000378:metabolism; D000426:Alcohol Dehydrogenase / Q000235:genetics / Q000378:metabolism; D001709:Biotechnology / Q000379:methods*; D000440:Butanols / Q000378:metabolism*; D046969:Clostridium acetobutylicum / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D015256:Coenzyme A-Transferases / Q000235:genetics / Q000378:metabolism; D006863:Hydrogen-Ion Concentration
chemical_list: D000440:Butanols; D000096:Acetone; D000426:Alcohol Dehydrogenase; D015256:Coenzyme A-Transferases