Production of three phenylethanoids, tyrosol, hydroxytyrosol, and salidroside, using plant genes expressing in Escherichia coli

Polyphenols, which include phenolic acids, flavonoids, stilbenes, and phenylethanoids, are generally known as useful antioxidants. Tyrosol, hydroxytyrosol, and salidroside are typical phenylethanoids. Phenylethanoids are found in plants such as olive, green tea, and Rhodiola and have various biological activities, including the prevention of cardiovascular diseases, cancer, and brain damage. We used Escherichia coli to synthesize three phenylethanoids, tyrosol, hydroxytyrosol, and salidroside. To synthesize tyrosol, the aromatic aldehyde synthase (AAS) was expressed in E. coli. Hydroxytyrosol was synthesized using E. coli harboring AAS and HpaBC, which encodes hydroxylase. In order to synthesize salidroside, 12 uridine diphosphate-dependent glycosyltransferases (UGTs) were screened and UGT85A1 was found to convert tyrosol to salidroside. Using E. coli harboring AAS and UGT85A1, salidroside was synthesized. Through the optimization of these three E. coli strains, we were able to synthesize 531 mg/L tyrosol, 208 mg/L hydroxytyrosol, and 288 mg/L salidroside, respectively.