Application of room-temperature ionic liquids in biocatalysis: Opportunities and challenges

Biocatalysis is now a key technology in the synthesis of chiral pharmaceuticals and agrochemicals. In order to deal with the low aqueous solubility of many substrates, biocatalytic processes are frequently performed in organic media to facilitate conversions at higher overall concentrations. This poses problems, however, since organic solvents are known to damage bacterial cell membranes and promote enzyme denaturation. Recent work has established that ionic liquids can successfully replace organic solvents in a range of whole cell and isolated enzyme bioconversions. In most examples studied to date, reaction rates and yields are comparable to, or greater than, those obtained in previously optimised organic systems. Significant enhancements in biocatalyst stability have also been observed. This chapter reviews the opportunities for using ionic liquids in biocatalytic processes and outlines key research themes that remain to be addressed. In particular the potential of ionic liquids as "designer solvents" for bioconversions will be described.