Lipase‐Catalyzed Hydrolysis of α‐Phenylethyl Esters in a Hydrophobic Ionic Liquid‐Based Bicontinuous Microemulsion Stabilized by Zwitterionic Surfactant

In the present work, the biocompatible sulfobetaine‐type zwitterionic surfactant (SB‐n) was selected to construct hydrophobic ionic liquid (HIL)‐based bicontinuous microemulsion (BME). It is shown that the [C 8 mim][PF 6 ] (1‐octyl‐3‐methylimidazolium hexafluorophosphate)‐based BME stabilized by mixed SB‐8/SB‐16 is more suitable for the expression of lipase activity than that stabilized by a single SB‐12. It is also demonstrated that the lipase activity in the present BME is higher than in the corresponding droplet‐type microemulsion. The lipase‐catalyzed hydrolysis of racemic α‐phenylethyl esters was used as a model reaction. It is found that the yield and the enantiomeric excess (ee) value of the product α‐phenylethanol depend on the lipase sources. In the SB‐8/SB‐16‐stabilized BME, Candida antarctica lipase (B) has the best hydrolysis activity and stereoselectivity toward α‐phenylethyl esters. It is also found that the surfactant content, buffer pH and substrate chain length affect the yield and the ee value of the product. Under optimized conditions, a yield of 41 % and an ee value of ~100 % were obtained. The present study is helpful for the development of an effective and environmentally benign medium for lipase‐based conversions.