The suitability of two different imidazolium-based families of ionic liquids (ILs) involving alkylsulfate and alkylsulfonate anions to act as solvents in an aqueous biphasic system for the extraction of lipase A from Candida antarctica has been investigated. Both high charge-density salts and aminoacids have been studied in order to evaluate both their potential as two-phase forming agents and as stabilizers of the active conformation of the enzyme. Extraction with 1-ethyl-3-methylimidazolium butyl sulfate [C2MIM][C4SO4] with ammonium sulfate affords an enzyme recovery of 99%. The structural conformation of the enzyme was analyzed by Fourier transform infrared data. (c) 2011 Elsevier B.V. All rights reserved.