Laccase-Catalyzed Reactions in Ionic Liquids for Green Sustainable Chemistry

Biocatalysis is an important and enabling tool in organic synthesis, degradation of chemical compounds, and biosensors. Laccases are copper ions containing oxidase and catalyze the conversion of polyphenol or amine derivatives using molecular oxygen. Recently, significant interests have gained attention for the development of a biochemical degradation method of lignocellulosic materials from the standpoint of green sustainable chemistry. Since these compounds are highly oxidized compounds, it is difficult to convert them stereo- or chemo-selectively to high-value small molecules. Chemical oxidations generally require hazardous reagents and harsh reaction conditions; hence, the resulting produced compounds are generally low-value molecules or complicated mixtures. On the contrary, laccases allow hazardous-reagent-free highly selective oxidative chemical conversions. The reactivity of the enzymes is influenced by a set of reaction conditions, in particular, the solvent system. Ionic liquids (ILs) have now been acknowledged as useful reaction media for biotransformations. Laccase-mediated reactions in ILs have been reviewed and focused on four topics: the first is "laccase-catalyzed reactions in ILs". The second is "biosensor system using laccase-mediated reaction in ILs". The third is "improved stability of laccase by immobilization or IL type additives", and the last chapter is "improved activity of laccase in ILs by protein engineering". Our opinion toward future perspectives of laccase-mediated reactions has also been discussed in "conclusions and future perspectives".