Intracellular Lipases for Enzymatic Synthesis of Phenylalanine Butyramide in a Biphasic Reaction System

Phenylalanine butyramide (FBA) is a novel butyric acid derivative with favorable sensory properties, which has broad prospects in medicine and feed processing. However, there is currently limited research on the enzymatic synthesis of FBA. As is well known, lipase plays a crucial role in amide bond synthesis, but it typically requires completely anhydrous conditions. The lipase from Sphingomonas sp. HXN-200 (SpL) is the only intracellular lipase identified to date, capable of catalyzing the ammonolysis of esters or acids in an aqueous phase. In this study, we developed a method for the synthesis of FBA catalyzed by SpL in a biphasic reaction system of water and n-hexane. SpL was successfully expressed in E. coli BL21, and the optimal induction conditions were 0.4 mM IPTG and 18 h. It was ascertained that the n-hexane system containing 2% water was conducive to the reaction. Under optimized reaction conditions, 0.89 mg/mL of FBA was obtained within 15 h at 30 °C. Additionally, we found that SpL also has the ability to hydrolyze amides in the reaction of SpL catalyzing the formation of amides, so we further analyzed its catalytic mechanism.