NOVELTY - Preparing butanol in a fermentation broth in a fermentor comprises: (a) providing a liquid fermentation broth comprising a carbohydrate substrate, nutrients, and water in which an alcohol is produced by the growth of Lactobacillus or a recombinant Lactobacillus; (b) contacting an ionic liquid with the fermentation broth, or its portion, to form an ionic liquid phase and an aqueous phase, where the butanol, or its portion, is more soluble in the ionic liquid phase than the aqueous phase; and (c) separating the butanol-rich ionic liquid phase from the aqueous phase.    USE - The process is useful for preparing butanol in a fermentation broth in a fermentor (claimed) to be used as fuels or fuel additives.    ADVANTAGE - The process allows for the product to be recovered using in-situ product removal (ISPR) techniques. It uses an ionic liquid to serve as a solvent to separate an alcohol product from a fermentation broth. Ionic liquids will generally have no measurable vapor pressure, and because of the availability of ionic liquids that have high solubility for the alcohol product, are immiscible with the aqueous fermentation broth, and have little to no toxicity to the microorganism.    DETAILED DESCRIPTION - Preparing butanol in a fermentation broth in a fermentor comprises: (a) providing a liquid fermentation broth comprising a carbohydrate substrate, nutrients, and water in which an alcohol is produced by the growth of Lactobacillus or a recombinant Lactobacillus; (b) contacting an ionic liquid with the fermentation broth, or its portion, to form from the resulting mixture an ionic liquid phase and an aqueous phase, where the butanol, or its portion, is more soluble in the ionic liquid phase than the aqueous phase; and (c) separating the butanol-rich ionic liquid phase from the aqueous phase; and optionally, recovering the butanol from the ionic liquid phase; where the ionic liquid comprises (i) a cation selected from pyridinium, imidazolium, or phosphonium, and (ii) an anion selected from tetrafluoroborate, hexafluorophosphate, 1,1,2,3,3,3-hexafluoropropanesulfonate, tris(pentafluoroethyl)trifluorophosphate, 1,1,2-trifluoro-2-(perfluoroethoxy)ethanesulfonate, 1,1,2-trifluoro-2-(perfluoromethoxy)ethanesulfonate, 2-(1,2,2,2-tetrafluoroethoxy)-1,1,2,2-tetrafluoroethanesulfonate, bis(pentafluoroethylsulfonyl)imide, or bis(trifluoromethylsulfonyl)imide.