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Extractive fermentation using aqueous biphasic systems (ABS) is a promising separation process since it provides a nondenaturing environment for biomolecules and improves the stability of cells. Due to environmental concerns and toxicity issues related with common volatile organic solvents, ionic liquids (ILs), a new class of nonvolatile alternative solvents, are being currently investigated for extraction purposes. In this work, a wide range of imidazolium-based ILs was studied aiming at obtaining new insights regarding their ability toward the formation of ABS and their capacity to the extraction of biomolecules. On the basis of the IL cations 1-ethyl-3-methylimidazolium and 1-butyl-3-methylimidazolium, the IL anion influence on ABS formation was assessed through their combination with chloride, bromide, acetate, hydrogensulfate, methanesulfonate, methylsulfate, ethylsulfate, trifluomethanesulfonate, trifluoroacetate, and dicyanamide. Ternary phase diagrams (and respective tie-lines) formed by these hydrophilic ILs, water, and the inorganic salt K(3)PO(4), were measured and are reported. The results indicate that the ability of an IL to induce ABS closely follows the decrease in the hydrogen bond accepting strength or the increase in the hydrogen bond acidity of the IL anion. In addition, the extraction capacity of the studied ABS was evaluated through their application to the extraction of an essential amino acid, L-tryptophan. It is shown that the partition coefficients obtained between the IL and the K(3)PO(4)-aqueous rich phases were substantially larger than those typically obtained with polymers-inorganic salts or polymers-polysaccharides aqueous systems.

In addition to the large range of applications proposed in literature, ionic liquids (ILs) have been recently reported to be able to form aqueous biphasic systems (ABS). They could thus be interesting media in biotechnological applications for the separation and purification of vital biomolecules. Therefore, in this work, a systematic study involving a large number of imidazolium-based ILs was conducted to provide new information related to ILs' ABS-promoting capability and extraction ability. For that purpose, the influence of the number of alkyl groups present at the cation, the cation side alkyl chain length, and the presence of double bonds, aromatic rings, and hydroxyl groups on this alkyl chain were evaluated. Ternary phase diagrams of the ABS formed by these ILs and K(3)PO(4) and the respective tie-lines were measured and presented. The ABS here investigated were further characterized for the first time accordingly to their extractive potential for amino acids, where l-tryptophan was selected as a model biomolecule. The partition coefficients here obtained were shown to be substantially larger than those observed in conventional ABS, demonstrating therefore the fine potential of IL-based ABS for biomolecules separation and purification.