Method for producing butanol using extractive fermentation

A method for recovering butanol from a fermentation medium, the method comprising:

• (a) providing a fermentation medium comprising butanol, water, and a recombinant microorganism comprising a butanol biosynthetic pathway, wherein the recombinant microorganism produces butanol;
• (b) contacting the fermentation medium with a water immiscible organic extractant composition comprising a solvent selected from the group consisting of C12 to C22 fatty alcohols, C12 to C22 ethers, esters of C12 to C22 fatty acids, C10 to C22 alkanes, and mixtures thereof, to form a butanol-containing organic phase and an aqueous phase,
• wherein the solvent is biocompatible with the microorganism such that at least about 90% of the microorganisms are viable after exposure to the organic extractant composition, and
• wherein the solvent has a boiling point less than about 300° C, with the proviso that the organic extractant is not oleyl alcohol, 1-dodecanol, behenyl alcohol, cetyl alcohol, myristyl alcohol, or stearyl alcohol;
• and
• (c) recovering the butanol from the butanol-containing organic phase.