“…Butanol, the main product of ABE fermentation, shows severe inhibition to the cells, which results in the low butanol yield and productivity [9,10]. More importantly, the recovery of butanol from the low titer fermentation broth has been recognized to be energy intensive [11,12]. Although efforts have been taken to construct metabolic engineering strains, however, there was only $2% of butanol in the broth when such skills were applied in the solventogenic fermentation, which was far behind the bio-ethanol titer (12-15%) [8,13].…”