Hydrophobic deep eutectic solvents-lipase synergistically catalyze the synthesis of Vitamin E succinate via hydrogen bonds

The low tolerance of lipases in organic solvents limits the industrial applications of enzymatic synthesis of Vitamin E succinate (VES). In this study, the deep eutectic solvents (DESs) were adopted as mediums to achieve the high efficiency and low-cost enzymatic synthesis of VES. Several kinds of commonly used DESs, including hydrophilic and hydrophobic DESs were screened firstly and fortunately found that the decanoic acid: lidocaine (DecA: Lid 2:1) performed best in the enzymatic synthesis of VES with a yield of 98.21 +/- 0.63 % at 50 celcius in only 6 h, which was significantly improved compared to previous studies. Interestingly, a synergistic effect of lipase and DESs was found in the enzymatic synthesis of VES, and the results of molecular simulations and density functional calculation suggested that it can be attributed to that 1) the hydrogen bonds interaction between DecA:Lid (2:1) and succinic anhydride enhances the electrophilicity of succinic anhydride and promotes the esterification reaction, 2) DecA:Lid (2:1) causes conformational changes of CRL via hydrogen bonds, which improves its capacity to capture and locate substrate molecules and thus enhancing its catalytic efficiency.