Biosynthetic Pathway for Ethyl Butyrate Production in .

Ethyl butyrate is one of the most important flavor substances in Chinese Baijiu and is also an ingredient in various daily-use chemical essences and food flavorings. In this study, to produce ethyl butyrate, we first introduced a butyryl-CoA synthesis pathway into . Subsequently, three different alcohol acyltransferases, , , and , were separately introduced into to catalyze the reaction of butyryl-CoA with ethanol to produce ethyl butyrate, and the results showed that strain EBS with produced the most ethyl butyrate (20.06 ± 2.23 mg/L). Furthermore, as the reaction catalyzed by to produce butyryl-CoA from crotonyl-CoA is a rate-limiting step, we replaced with , and the modified strain EST produced 77.33 ± 4.79 mg/L ethyl butyrate. Finally, the copy numbers of and were further increased, and the resulting modified strain EST-dST produced 99.65 ± 7.32 mg/L ethyl butyrate.