The effects of ionic liquid media on the activity of Candida antarctica lipase B in a simple transesterification reaction were studied. In ionic liquids containing dicyanimide, alkylsulfate, nitrate and lactate anions, which dissolved CaLB, the reaction was at least ten times slower than in [BMIm][BF4]. Only [Et3MeN][MeSO4] was an exception, as dissolved CaLB maintained its activity in this solvent. A cross-linked enzyme aggregate of CaLB was twice as active in [BMIm][dca] as in tert-butyl alcohol, whereas the free enzyme was irreversibly deactivated in this latter ionic liquid.
