Toward Green Processes for Fine Chemicals Synthesis: Biocatalysis in Ionic Liquid—Supercritical Carbon Dioxide Biphasic Systems

Enzymatic transformations in ionic liquids (ILs)/supercritical carbon dioxide (scCO 2 ) biphasic systems, whereby enzyme molecules are "immobilized" in the IL phase and substrates/products are transported by the scCO 2 phase, are described as a way for carrying out clean synthetic chemical processes to produce pure products, being. Task-specific ionic liquids (TSILs), based on quaternary ammonium cations, with functional side chains (trimethylydroxylpropyl-, trimethylbutyronitryl-, trimethylhexylonitryl-, trimethylbutyl-and trimethylhexyl-), associated with the same anion (bis(trifluoromethane)sulfonylamide), were assayed for Candida antarctica lipase B (CALB)-catalyzed ester synthesis in IL/scCO 2 biphasic systems. The suitability of these ILs was established from both the activity and stability of the enzyme, including the maintenance of the secondary structure of the protein using circular dichroism spectroscopy. The mass-transfer phenomena between IL/scCO 2 phases were found to be key parameters for the efficient design of synthetic processes in these systems.