One-Pot Efficient Biosynthesis of 4-Hydroxyphenylacetic Acid and Its Analogues from Lignin-Related p-Coumaric and Ferulic Acids

4-Hydroxyphenylacetic, homovanillic, and 3,4-dihydroxyphenylacetic acids are phenolic acids with various attractive bioactivities, such as antioxidative, anti-inflammatory, and antiobesity effects. However, powerful strategies for the efficient and sustainable synthesis of hydroxyphenylacetic acids are lacking. In this work, to promote the synthesis of hydroxyphenylacetic acids, we first engineered an Escherichia coli BL21 (DE3)-reduced aromatic aldehyde reduction strain to accumulate their aromatic aldehyde precursors. Then, we developed a one-pot bioconversion strategy using lignin-related p-coumaric and ferulic acids as starting materials for the abovementioned synthesis. The bioconversions comprise two artificial routes: decarboxylation-epoxidation-isomerization-oxidation for the synthesis of 4-hydroxyphenylacetic and homovanillic acids and decarboxylation-epoxidation-isomerization-oxidation-hydroxylation for the synthesis of 3,4-dihydroxyphenylacetic acid. This enabled efficient biosynthesis of 4-hydroxyphenylacetic acid (13.7 mM, 91.3% yield, 1041 mg/L/h productivity), homovanillic acid (3.8 mM, 76.2% yield, 115.6 mg/L/h productivity), and 3,4-dihydroxyphenylacetic acid (13.5 mM, 90% yield, 907 mg/L/h productivity). Moreover, we made an example to investigate the synthesis of hydroxyphenylacetic acids from the lignocellulosic biomass hydrolysate, in which 5.2 mM 4-hydroxyphenylacetic acid in 57.8% conversion and 2.2 mM 3,4-dihydroxyphenylacetic acid in 55% conversion were produced from 9 and 4 mM p-coumaric acid, respectively. This study provides not only a new strategy to enable the efficient and sustainable synthesis of hydroxyphenylacetic acids but also new insights into the utilization of lignocellulosic biomass in the synthesis of high-value compounds.