Patent ID: 8283505

Claim:
A method for producing isobutanol comprising: (a) culturing a microorganism capable of producing isobutanol in a fermentor, thereby forming a fermentation broth comprising microorganisms and isobutanol; (b) removing a portion of the fermentation broth from the fermentor; (c) distilling the portion, thereby forming an isobutanol-depleted liquid phase and an isobutanol-enriched vapor phase comprising water and isobutanol; (d) condensing the isobutanol-enriched vapor phase formed in step (c), thereby forming an isobutanol-rich liquid phase and a water-rich liquid phase; and (e) separating the isobutanol-rich phase liquid from the water-rich liquid phase using a liquid-liquid separator; wherein: (1) said steps (b)-(e) are conducted simultaneously with step (a); (2) the isobutanol-depleted liquid phase comprises viable microorganisms; and (3) the isobutanol-depleted liquid phase is returned to the fermentor.