Production of Isopropanol-Butanol-Ethanol As a Fuel By Metabolic Engineering of Clostridial Species

1-Butanol is an attractive biofuel that can replace gasoline, but its low octane rate might lead to abnormal combustion. In the present study, we developed engineered Clostridium acetobutylicum strains that can produce high amount of isopropanol-butanol-ethanol (IBE) mixture. In addition to introduction of the adhB-593 gene encoding NADPH-dependent primary/secondary alcohol dehydrogenase, co-overexpression of the hydGB-593 gene encoding putative ferredoxin:NADP+ reductase improved IBE titer further. The final strain was employed as a host for a large-scale fermentation to examine its possibility for industrial IBE production. Even though the genomes of many clostridial strains harbor the orthologous genes to hydGB-593, C. acetobutylicum does not harbor this gene. Our results suggest that C. acetobutylicum might have a different mechanism of NADPH regeneration from those in other clostridial species, and the introduction of hydGB-593 might enhance the NADPH regeneration in C. acetobutylicum. [This work was supported by the Technology Development Program to Solve Climate Changes on Systems Metabolic Engineering for Biorefineries from the Ministry of Science, ICT and Future Planning (MSIP) through the National Research Foundation (NRF) of Korea (NRF-2012M1A2A2026556 and NRF-2012M1A2A2026557) and by the C1 Gas Refinery Project funded by the MSIP through the NRF of Korea (2015M3D3A1A01064918).]