Efficient biosynthesis of 3, 4-dihydroxyphenylacetic acid in Escherichia coli

3, 4-Dihydroxyphenylacetic acid (3, 4-DHPA) is a phenolic acid with strong anti-oxidative activity, showing potential applications in food and pharmaceutical industries. In this study, a 3, 4-DHPA biosynthetic pathway was designed by connecting 4-hydroxyphenylacetic acid (4-HPA) biosynthesis with its hydroxylation. The starting strain produced only 46 mg/L of 4-HPA in 48 h. Enhancing the shikimate pathway increased the titer by 19-fold to 923 ± 57 mg/L. Furthermore, pykA and pykF were disrupted to conserve phosphoenolpyruvate for 4-HPA production. With this effort, 4-HPA titer was increased to 1817 ± 55 mg/L. Introducing the hydroxylase HpaBC into the 4-HPA overproducing strain resulted in 3, 4-DHPA production and the best strain produced 1856 ± 67 mg/L of 3, 4-DHPA in shake flask cultures. This work reports de novo biosynthesis of 3, 4-DHPA for the first time and provides a promising alternative for sustainable production of this valuable compound.