Butyrate-based n-butanol production from an engineered Shewanella oneidensis MR-1

n-Butanol is considered as the next-generation biofuel, because its physiochemical properties are very similar to fossil fuels and it could be produced by Clostridia under anaerobic culture. Due to the difficulties of strict anaerobic culture, a host which can be used with facultative environment was being searched for n-butanol production. As an alternative, Shewanella oneidensis MR-1, which is known as facultative bacteria, was selected as a host and studied. A plasmid containing adhE2 encoding alcohol dehydrogenase, various CoA transferases (ctfAB, atoAD, pct, and ACT), and acs encoding acetyl-CoA synthetase were introduced and examined to S. oneidensis MR-1 to produce n-butanol. As a result, ctfAB, acs, and adhE2 overexpression in S. oneidensis-pJM102 showed the highest n-butanol production in the presence of 2% of N-acetylglucosamine (NAG), 0.3% of butyrate, and 0.1 mM of IPTG for 96 h under microaerobic condition. When more NAG and butyrate were fed, n-butanol production was enhanced, producing up to 160 mg/L of n-butanol. When metal ions or extra electrons were added to S. oneidensis-pJM102 for n-butanol production, metal ion as electron acceptor or supply of extra electron showed no significant effect on n-butanol production. Overall, we made a newly engineered S. oneidensis that could utilize NAG and butyrate to produce n-butanol. It could be used in further microaerobic condition and electricity supply studies.