In organic reactions chemical catalysts as well as catalytic proteins are used. Biocatalysts have become a useful tool for organic chemists, allowing selective, one-step syntheses. Lipases, hydrolytic enzymes, have gained a considerable attention . Lipase-catalyzed reaction proceeds according to the "bi-bi ping-pong" (Scheme 1) . Catalytic potential of lipases allows to obtain a wide range of organic compoundsby formation of C-C, C-N, and C-S bonds [6–8]. Enzyme-catalyzed reactions depend on change of basic-acidic properties or redox potential and an applicationof appropriate solvent can increase the control over chemical balance. The solvent used as the reaction medium should allow enzyme stability, increase its activity and selectivity. In organic hydrophobic solvents, enzyme is more stable and selective, its activity, however, is reduced in comparison to polar solvents [6–8]. During a search for optimal solvent special attention was paid to a typical organic solvents – ionic liquids. Ionic liquids are organic salts (Scheme 2) [9–13]. They do not mix with hydrophobic solvents such as hexane (Tab. 2) [9, 12, 13, 23] and their polarity is similar to low molecular weight alcohols (Tab. 3) [9, 12, 13, 22, 23, 32]. Because of their specific physical properties, ionic liquids may be optimal microenvironment for enzymes, influencing their activity and stability. CALB is widely used in organic syntheses because of its adaptive capability (Tab. 1) as well as regio- and enantioselective properties [18–21]. Due to its exceptional conformation stability in ionic liquids, CALB can be successfully applied both in heterogeneous (Tab. 4) [22, 36] and homogeneous catalysis (Scheme 4, Tab. 5) . The activity of CALB after incubation in ionic liquids is comparable or greater than in conventional organic solvents (Tab. 6, Fig. 1) [9, 13, 23, 38]. A solvent used as a reaction medium should help to maintain enzyme stabilizing its active conformation and protecting it from deactivating factors such as temperature and scCO2 (Tab. 7) [38–43]. Some ionic liquids constitute a bridge between conventional organic solvents and physiological enzyme environment. They provide exceptional activity of catalytic proteins, which allows efficient and selective reaction catalysis (Tab. 8) [6,38–40, 43–61].