NOVELTY - A method (M1) for extracting at least one organic compound from an aqueous mixture involves contacting the aqueous mixture with an extraction liquid of ether compound to produce a biphasic composition; and separating at least a portion of the extraction liquid phase from the aqueous phase to provide an extract solution comprising the organic compound.    USE - For extracting at least one organic compound from an aqueous mixture; as an in situ extraction method of fermentation broth fermentation; for producing transportation fuel, where the transportation fuel is a bio-fuel derived from biomass (claimed). For in situ extraction of products or by-products from fermentation reaction; for isolating or purifying organic compounds such as lower aliphatic carboxylic acids e.g. acetic acid, lower alcohols such as ethanol and certain substituted aromatic compounds such as phenols, furans and anisoles, and for extraction of useful organic compounds from fermentation e.g. for production of biofuels from lignocellulosic feedstocks.    ADVANTAGE - The method extracts organic compound, which is a fermentation product that inhibits the fermentation reaction, and extraction of such organic compound reduces inhibition by the fermentation product. The method allows removal of compounds such as acetic acid or ethanol from complex aqueous mixtures including fermentation reactions or broths. The method uses non-aqueous solution from which the organic compounds can be easily recovered. The method is simple and inexpensive. The method provides efficient method for extracting small, polar organic molecules from aqueous mixtures; and permits easy recovery of fermentation products from aqueous mixtures. The method is an effective, energy-efficient liquid-liquid extraction method to separate organic compounds such as aromatic compounds, acetic acid and other lower carboxylic acids, lower alcohols, and various small, polar organics from aqueous mixtures. The method shows low solubility of water in the extraction liquid, which simplifies removing virtually all of the water from the organic product. The method uses solvents having high boiling points and high stability, which enables the user to conveniently separate more volatile organic compounds like acetic acid, ethanol, isobutanol or other low-boiling organics from the extraction liquid by distillation. Even organic compounds present at very low concentrations (e.g. less than 1 wt.) can be extracted from aqueous mixtures by these methods, so they provide a viable way to collect organic compounds that are formed or liberated in an aqueous system, such as fermentation products, and to remove organic compounds efficiently for purposes of cleaning the aqueous layer. The methods can be used to collect or remove organic products from fermentation broths in situ i.e. without stopping the fermentation process; it can be used advantageously in combination with fed-batch fermentation methods to increase the efficiency of the fermentation e.g. by removing inhibitory products from the fermentation to allow it to proceed more rapidly and completely. The fed-batch methodology enables the fermentation reactions to operate at higher effective concentrations, increasing the output from a given reactor volume; this extraction methodology used in combination with a fed-batch fermentation can prevent product or by-product build-up in the high-concentration fed batch process from inhibiting the reaction. The extraction method uses a carefully tailored extraction liquid that is not miscible with water but is sufficiently polar to extract even small, polar organic compounds with reasonably good efficiency, though they do not appreciably extract saccharides from water. The method is suitable for extracting organic compounds that have a lower boiling point than the chosen extraction liquid, so the extracted organics can be distilled out of the extraction liquid without having to distill away the relatively larger volume of the extraction liquid. This also permits convenient recycling of the extraction liquid.    DETAILED DESCRIPTION - A method (M1) for extracting at least one organic compound from an aqueous mixture, involves contacting the aqueous mixture with an extraction liquid containing a compound of formula R-O-(CH2)2-3-O-(CH2)2-3-O-R (I), R'-O-(CH2)2-O-(CH2)2-O-(CH2)2-O-R' (II) or R'a-O-CH2-CH(O-R'a)-CH2-O-R'a (III) to produce a biphasic composition; and separating at least a portion of the extraction liquid phase from the aqueous phase to provide an extract solution comprising the organic compound.    R and R'=3-5C alkyl;    R'a=3-5C alkyl or 3-5C acyl.    INDEPENDENT CLAIMS are included for the following:    (1) a method (M2) to remove at least a portion of acetic acid from an aqueous mixture, involving contacting the aqueous mixture with a first portion of an extraction liquid containing compound of formula (I), (II) or (III) to form a biphasic mixture having an aqueous phase and a first extraction liquid phase, so that at least a portion of the acetic acid migrates from the aqueous liquid into the first extraction liquid phase, and separating at least a portion of the first extraction liquid phase from the biphasic mixture;    (2) a continuous process (M3) for extracting an organic compound from an aqueous mixture;    (3) a method (M4) to convert biomass into acetic acid and/or ethanol, involving: a) contacting saccharides derived from biomass with a fermenting microorganism in an aqueous carrier to provide a fermentation mixture; b) maintaining the fermentation mixture under fermentation conditions to permit acetic acid and/or ethanol to form in the fermentation mixture; and c) contacting the fermentation mixture with an extraction liquid to form a biphasic composition having an aqueous carrier phase and an extraction liquid phase, thereby extracting at least a portion of the acetic acid and/or ethanol and/or isobutanol and/or n-butanol from the aqueous carrier phase into the extraction liquid phase; and    (4) a method (M5) to produce transportation fuel involving extracting an organic compound from an aqueous mixture by the method (M1) to (M4).