Key factors affecting the activity and stability of enzymes in ionic liquids and novel applications in biocatalysis

•Hydrophobic and less viscous ILs can enhance the activity and stability of enzymes.•Kosmotropic anion and chaotropic cation in ILs are beneficial to dissolving enzyme.•The properties of ILs affecting enzymes’ stability and activity have correlations.•New methods like modified enzyme charge are also effective to stabilize enzymes.•ILs can be used as non-solvents in biochemical engineering.

Ionic liquids as eco-friendly solvent media and catalyst play very important roles in many enzymatic reactions such as enzymatic biotransformation and all kinds of biosynthesis due to their unique and tunable physical properties. The changes of the cations or anions types in ionic liquids have important effects on the activity, stability and structures of enzymes. In this critical review, we systematically shed light on the key factors affecting the activity and stability of enzymes in ILs and discussed the relationships among these factors. Moreover, the strategies for improving the enzymes’ utility in ionic liquids are exhibited. Finally, we address some novel industrial applications of ionic liquids in biochemical engineering such as the pretreatment of lingocellulosic biomass, transesterification in biodiesel synthesis and non-solvents in biotransformations. This review will thus be helpful for the researchers of various biocatalytic applications.

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