Redox self-sufficient production of hydroxytyrosol from dopamine by enzymatic cascade catalysis

Abstract

Due to its powerful antioxidant capacity, hydroxytyrosol (HT) has a long history of application in the cosmetics and food industries. Owing to the fact that current isolation procedures for HT, both natural and synthetic, are not optimal, the efficient acceleration of HT synthesis is a critical problem in biocatalysis and metabolic engineering. The purpose of this study is to establish an Escherichia coli (E. coli) whole cell system capable of synthesizing HT from dopamine by using chosen enzymes to construct a custom biosynthetic pathway. The modified strain E. coli HT3 generated 4.43 g/L of HT under ideal conditions, with a yield and productivity of 0.44 g/L/h in shaking tube. Using alanine dehydrogenase (AlaDH), a “bridge” between the amine and its equivalent alcohol was created in the system. Specifically, ω-transaminase (ω-TA) were identified as the rate-limiting enzymes in the formation of HT using fast investigations employing cell-free systems. Subsequently, overexpression of ω-TA, AlaDH, and weakly overexpressed alcohol dehydrogenase (ADH), efficiently boosted HT synthesis based on a whole-cell biocatalyst system. Furthermore, this establishes a biocatalytic pathway for the synthesis of new building blocks for industrially high-performance HT.