The isobutanol productivity was approximately twofold and the titer was 9% higher than n-butanol produced by Clostridium in a similar integrated system.Keywords: Biofuels, Isobutanol, E. coli, Gas stripping, BioreactorIntroductionThe growing need for alternative energy calls for new strategies to produce liquid fuels such as alcohols, alkanes, and fatty acid esters (or biodiesel) from renewable so