NOVELTY - Recovering (I) butanol from a fermentation medium, comprises: (a) providing a fermentation medium comprising butanol, water, at least one electrolyte 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) 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 electrolyte at a concentration sufficient to increase the butanol partition coefficient relative to that in the presence of the salt 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 electrolyte at a concentration at least sufficient to increase the butanol partition coefficient relative to that in the presence of the salt concentration of the basal fermentation medium, and a genetically modified microorganism that produces butanol from at 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) 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 which comprises an aqueous phase and (a1) and (b1) as above per se, where the biphasic fermentation medium further comprises electrolyte at a concentration sufficient to increase the butanol partition coefficient relative to that in the presence of the salt concentration of the basal fermentation medium, 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) producing (III) 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 electrolyte 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; (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 comprising butanol, water, electrolyte at a concentration at least sufficient to increase the butanol partition coefficient ion medium, 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)