NOVELTY - Recovering (I) butanol from a fermentation medium, comprises: (a) providing a fermentation medium comprising butanol, water, at least one osmolyte and a genetically modified microorganism; (b) contacting the fermentation medium with (a1) a first water-immiscible organic extractant and optionally (b1) a second water-immiscible organic extractant to form a two-phase mixture comprising an aqueous phase and a butanol-containing organic phase; and (c) optionally, recovering the butanol from the butanol-containing organic phase to produce recovered butanol.    USE - The methods are useful for recovering butanol from fermentation medium and producing butanol, preferably 1-butanol, 2-butanol or isobutanol (all claimed), which is used as fuel or biofuel additive.    ADVANTAGE - The genetically modified microorganism utilized in the methods: comprises a modification which inactivates a competing pathway for carbon flow; and does not produce acetone. The methods provide butanol: having energy content similar to that of gasoline and can be blended with any fossil fuel; having the potential of impacting hydrogen distribution problems in the emerging fuel cell industry; which can be easily reformed for its hydrogen content, and distributed through existing gas stations in the purity required for either fuel cells or vehicles; which is produced from plant derived carbon sources, thus avoids the negative environmental impact associated with standard petrochemical process; at net effective rate, titer, and with high yield in an economical manner than the threshold levels of butanol obtained by a two phase extractive fermentation process without the addition of osmolyte at a concentration sufficient to increase the butanol partition coefficient relative to that in the presence of the osmolyte concentration of the basal fermentation medium; and which is less corrosive than ethanol. The methods also reduce the net amount of fresh or recycled extractant needed to achieve a desired level of butanol production from a batch fermentation.    DETAILED DESCRIPTION - Recovering (I) butanol from a fermentation medium, comprises: (a) providing a fermentation medium comprising butanol, water, at least one osmolyte at a concentration at least sufficient to increase the butanol partition coefficient relative to that in the presence of the osmolyte concentration of the basal fermentation medium and an optional fermentable carbon source, and a genetically modified microorganism that produces butanol from least one fermentable carbon source; (b) contacting the fermentation medium with (a1) a first water-immiscible organic extractant comprising 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 optionally (b1) a second water-immiscible organic extractant comprising 7-22C fatty alcohols, 7-22C fatty acids or carboxylic acid, esters of 7-22C fatty acids or carboxylic acid, 7-22C fatty aldehydes and/or 7-22C fatty amides to form a two-phase mixture comprising an aqueous phase and a butanol-containing organic phase; and (c) optionally, recovering the butanol from the butanol-containing organic phase to produce recovered butanol. INDEPENDENT CLAIMS are also included for:    (1) producing (II) butanol comprising: (a2) providing a genetically modified microorganism that produces butanol from at least one fermentable carbon source; (b2) growing the microorganism in a biphasic fermentation medium comprising an aqueous phase and (a1) and (b1) as above per se, where the biphasic fermentation medium further comprises osmolyte at a concentration sufficient to increase the butanol partition coefficient relative to that in the presence of the osmolyte concentration of the basal fermentation medium and fermentable carbon source, for a time sufficient to allow extraction of the butanol into the organic extractant to form a butanol-containing organic phase; (c2) separating the butanol-containing organic phase from the aqueous phase; and (d2) optionally, recovering the butanol from the butanol-containing organic phase to produce recovered butanol; and    (2) production (III) of butanol comprising: step (a2) as above per se; (b3) growing the microorganism in a fermentation medium, where the microorganism produces the butanol into the fermentation medium to produce a butanol-containing fermentation medium; (c3) adding osmolyte to the fermentation medium; (d3) contacting at least a portion of the butanol-containing fermentation medium with (a1) and (b1) as above per se, to form a two-phase mixture comprising an aqueous phase and a butanol-containing organic phase; step (c2) as above per se; (e3) optionally, recovering the butanol from the butanol-containing organic phase; and (f3) optionally, returning at least a portion of the aqueous phase to the fermentation medium; and    (3) a composition comprising: a fermentation medium comprises butanol, water, osmolyte, and a genetically modified microorganism; and (a1) and (b1) as above per se, where the composition forms a two-phase mixture comprising an aqueous phase and a butanol-containing organic phase, thus butanol may be separated from the fermentation medium.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of the methods, in which the first extractant and the second extractant are combined in a vessel prior to contacting with the fermentation medium in a fermentation vessel.    Aqueous stream (10)    First extractant (12)    Optional second extractant (14)    Vessel (16)    Stream (18)