Effect of deep eutectic solvents on activity, stability, and selectivity of enzymes: Novel insights and further prospects

Abstract

Deep eutectic solvents (DESs) have been extensively concerned since 2008 as reaction media in biocatalysis because of their excellent solvent performances. Here, we try to clarify the effects of DESs on the catalytic properties, structure, and conformation of enzymes. Through comprehensive analysis, it is found that the catalytic properties of enzymes can be designed in different DESs through modulating the hydrogen bond acceptors, hydrogen bond donors, and their molar ratio. Structural changes of different enzymes in various DESs are not always consistent, which may be attributed to the original structure of enzymes, DES composition, and the interactions between enzymes and DESs. Moreover, we try to elucidate how DESs interact with varying amounts of water, and furthermore how water in DES affects the catalytic properties of enzymes. The available researches indicate that proper amount of water can integrate into the network of DESs and strengthen the hydrogen-bonding interactions while excessive water will destroy the integrity of DESs. Water affects the performance of enzymes in two possible ways: 1) affecting enzyme affinity and structure directly; 2) influencing the properties of DESs, thus modulating the efficiency of enzymes. This review paves road for researchers to design DESs with desired properties for specific applications.