3.8. Effect of ionic liquids on the enzyme activity
Ionic liquids (ILs) is with industrially attractive advantages for biocatalysis due to their tunable chemical properties. Several ionic liquids ([EMIM]BF4, [BMIM]Cl, [BMIM]BF4) were selected and added into the reaction system with final concentration as 5 mM (Fig. S4). The activity of DA11 in [BMIM]BF4 ionic liquid was 97.8%, while [EMIM]BF4 and [BMIM]Cl reduced the relative enzyme activity of DA11. It is reported that [BMIM]+ cations can strip off essential water molecules from the enzyme surface, which cause the decreased enzyme activity [33]. Ionic liquids also can affect enzyme activity through direct interaction with the enzyme and by altering the microenvironment of enzyme. Due to the conductivity and hydrophobicity, ILs are widely applied for electrode modification to obtain high heterogeneous electron transfer rates [34]. Therefore, ILs tolerant DA11 is promising for its application in biosensor.