Microbial synthesis of 4-hydroxybenzoic acid from renewable feedstocks

4-Hydroxybenzoic acid (4HBA) and its esterified forms can be used as preservatives in the pharmaceutical and food industries. Here, we reported the establishment of a coenzyme-A (CoA) free multi-enzyme cascade in Escherichia coli to utilize biobased _L-tyrosine for efficient synthesis of 4HBA. The multi-enzyme cascade contains _L-amino acid deaminase from Proteus mirabilis, hydroxymandelate synthase from Amycolatopsis orientalis, (S)-mandelate dehydrogenase and benzoylformate decarboxylase from Pseudomonas putida, and aldehyde dehydrogenase from Saccharomyces cerevisiae. The whole-cell biocatalysis afforded the synthesis of 128 ± 1 mM of 4HBA (17.7 ± 0.1 g/L) from 150 mM _L-tyrosine with > 85% conversion within 96 h. In addition, the artificial enzymatic cascade also allowed the synthesis of benzoic acid from 100 mM _L-phenylalanine with a conversion ∼ 90%. In summary, our research offers a sustainable alternative for synthesizing 4HBA and benzoic acid from renewable feedstocks.