Lid and tunnel dynamics guided the modification of chitosan by ionic liquids for enhancing its immobilization performance of Candida antarctica lipase B

Previous studies demonstrated that the modification of chitosan via ionic liquids (ILs) can significantly enhance the efficiency of immobilized enzymes. However, the huge number and kinds of ILs made it almost impossible to screen the most suitable ILs modifiers via experimental methods. Thus, in the present study, molecular dynamics (MD) simulation was adopted to investigate the binding mechanism of Candida antarctica lipase B (CALB) and ILs functionalized chitosan. The effects of various functional groups of ILs were firstly investigated and found that the hydroxyl group performed best. Moreover, the throughput, stability of tunnel, state of lid, and RMSF of key amino acids were found to be several important parameters during the immobilization, and a novel strategy based on these were successfully proposed with a scoring function to evaluate the activity and stability of immobilized lipase. To further evaluate it, the scoring function was adopted in the design of more suitable ILs modifiers, and the results showed that the CS2H exhibited 1.5 and 5.1 folds of stability and activity higher than free enzyme and may be the most suitable modified carrier. This study proposes a general strategy to screen and design the ILs modifiers during the immobilization of various enzymes.