(309b) Biphasic Biocatalysis with Ionic Liquids: Partitioning and Bacterial Toxicology

Whole-cell biocatalysis is used to produce a large variety of chemical and fuels. Efficient dosing of the substrate and extraction of the product can be a challenge for fermentation microorganisms that suffer from substrate or product inhibition. Biphasic biocatalysis with ionic liquids may overcome some of these issues. For any solvent including ionic liquids, two of the most important properties for biphasic systems are advantageous solute partitioning between the aqueous and solvent phase and low toxicity of the solvent to the microorganism. In the present work, the liquid-liquid equilibrium (partitioning) of solutes such as acetone, butanol, and (+)-cis-(1R,2S)-1,2-napthalene dihydrodiol (NDHD) between water and a model ionic liquid, 1-hexyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)amide ([HMIm][Tf2N]) have been measured. The results indicate that high partition coefficients and large selectivities over water can be achieved. In addition, toxicity of various ionic liquids to the Escherichia coli strain JM109(DE3) pDTG141 has been studied, with the aim to identify biocompatible hydrophobic ionic liquids. Molecular toxicity was measured and expressed as EC₅₀ by observing growth curves with various concentrations to the IL saturation point. The effect of the cation and anion has been investigated for imidazolium ionic liquids such as 1-alkyl-3-methylimidazolium [RMIm] salts, quaternary ammonium, pyridinium and phosphonium ionic liquids. Both the partitioning and toxicity will be compared to better understand the suitability of different classes of ionic liquids for whole-cell biocatalysis.