NOVELTY - Recovering (M1) butanol from fermentation medium involves providing fermentation medium comprising butanol, water, fermentable carbon source, and genetically modified microorganism that produces butanol from a fermentation medium; contacting the medium with water-immiscible extractant composition comprising first solvent e.g. 12-22C fatty alcohols, and second solvent e.g. 7-11C alcohols, to form two-phase mixture comprising aqueous phase and butanol-containing organic phase; separating the organic phase from aqueous phase; and recovering butanol from butanol-containing organic phase.    USE - For recovering butanol such as isobutanol from a fermentation medium (claimed). The butanol is used as biofuel or fuel additive.    ADVANTAGE - The method provides butanol having energy content similar to that of gasoline and which is blended with any fossil fuel. The method provides butanol which is favored as a fuel or fuel additive as it yields only carbon dioxide (CO2) and little or no sulfur oxide or nitrogen oxide when burned in the standard internal combustion engine; and which is less corrosive than ethanol, the most preferred fuel additive to date. The methods produce butanol from plant derived carbon sources, thus avoids the negative environmental impact associated with standard petrochemical processes for butanol production; has higher butanol partition coefficient which is obtained by the appropriate combination of first and second solvent, thus provides more effective extraction of butanol from the fermentation medium; has ability to use an extractant comprising a shorter carbon chain solvent which has a desirably higher partition coefficient but undesirably lower biocompatibility and to mitigate the lower biocompatibility by the combination with a longer carbon chain solvent, thus effective extractant is obtained; has improved process operability characteristics of the extractant relative to those characteristics of a longer carbon chain extractant such as oleyl alcohol.    DETAILED DESCRIPTION - Recovering (M1) butanol from a fermentation medium involves providing a fermentation medium comprising butanol, water, at least one fermentable carbon source, and a genetically modified microorganism that produces butanol from a fermentation medium containing at least one fermentable carbon source; contacting the fermentation medium with a water-immiscible extractant composition comprising a first solvent and a second solvent, where the first solvent is selected from 12-22C fatty alcohols, 12-22C fatty acids, esters of 12-22C fatty acids, 12-22C fatty aldehydes, and/or 12-22C fatty amides, and the second solvent is selected from 7-11C alcohols, 7-11C carboxylic acids, esters of 7-11C carboxylic acids, and/or 7-11C aldehydes, to form a two-phase mixture comprising an aqueous phase and a butanol-containing organic phase; separating the butanol-containing organic phase from the aqueous phase; and recovering the butanol from the butanol-containing organic phase to produce recovered butanol. INDEPENDENT CLAIMS are included for the following:    (1) production (M2) of butanol involving either: providing a genetically modified microorganism that produces butanol from a fermentation medium comprising at least one fermentable carbon source, growing the microorganism in a biphasic fermentation medium comprising an aqueous phase and a water-immiscible extractant composition comprising the first solvent and the second solvent, where the biphasic fermentation medium comprises the water-immiscible extractant composition (10-90 vol.%), for a time sufficient to allow extraction of the butanol into the extractant composition to form a butanol-containing organic phase, separating the butanol-containing organic phase from the aqueous phase, and recovering the butanol from the butanol-containing organic phase to produce recovered butanol; or providing a genetically modified microorganism that produces butanol from a fermentation medium comprising at least one fermentable carbon source, growing the microorganism in a fermentation medium where the microorganism produces the butanol into the fermentation medium to produce a butanol-containing fermentation medium, contacting at least a portion of the butanol-containing fermentation medium with a water immiscible extractant composition comprising the first solvent and second solvent, to form a two-phase mixture comprising an aqueous phase and a butanol-containing organic phase, separating the butanol-containing organic phase from the aqueous phase, recovering the butanol from the butanol-containing organic phase, and returning at least a portion of the aqueous phase to the fermentation medium; and    (2) two-phase mixture comprising: fermentation medium containing isobutanol, water, at least one fermentable carbon source, and a genetically modified microorganism that produces isobutanol from a fermentation medium, and water-immiscible organic extractant composition containing the first solvent and the second solvent.