Lipase and Metal Chloride Hydrate-Natural Deep Eutectic Solvents Synergistically Catalyze Amidation Reaction via Multiple Noncovalent Bond Interactions

With their extreme advantages in high surface activity, bacteriostasis, and low toxicity, lipoamino acids (LAA) attracted widespread academic and industrial interests. In this study, natural deep eutectic solvents (NADESs), were adopted as a medium of enzymatic synthesis of lauroyl glycine (LG). The highest yield of 50.49 ± 1.94% was obtained in the C-Gly system. Interestingly, a synergistic effect between CALB and NADESs was found in this section. We proposed that anions play a key role in this process. To explore it, metal chloride hydrates were added into C-Gly. Fortunately, seven kinds of three-constituent NADESs (3c-NADESs) with a low viscosity were successfully formed. All of these new-design solvents were used as a medium of enzymatic of LG, and the highest yield of LG can reach 85.97 ± 1.86% after optimization. To explore the mechanism of the synergistic effect between CALB and 3c-NADESs. The results of molecular dynamics studies (MD) showed that there was no significant change of CALB in this process, which indicated that CALB may play a secondary role in the synergistic effect. In this context, we studied the molecular interaction between Mg-CGly and lauric acid, and the reaction processes were studied in depth via IRC method. The results suggested that a strong H-bond was formed between Cl^– and lauric acid. This interaction may increase the electron-attracting ability of fatty acids and make them more susceptible to be attacked by amino acids and thus to increase the yield of amidation reaction of lauric acid and glycine.