Microbial synthesis of hydroxytyrosol and hydroxysalidroside

Plant-derived phenolic compounds, such as hydroxytyrosol and hydroxysalidroside, have a beneficial impact on human health owing to their antioxidant activity. In this study, we used Escherichia coli to synthesize hydroxytyrosol. Tyrosine decarboxylase from Papaver somniferum, tyrosine oxidase from Micrococcus luteus, and 4-hydroxyphenylacetate 3-monooxygenase from E. coli were transformed into the bacterial cell. The resulting transformant successfully synthesized hydroxytyrosol. Furthermore, we used the engineered E. coli strains to synthesize ~ 268.3 mg/L hydroxytyrosol. Three uridine diphosphate-dependent glycosyltransferases (UGTs), which were previously shown to convert tyrosol into salidroside, were tested to synthesize hydroxysalidroside, and one of UGTs was used to synthesize hydroxysalidroside from hydroxytyrosol. Finally, E. coli harboring this UGT converted approximately 50% of hydroxytyrosol into hydroxysalidroside.