Aromatics have many important applications in modern society but are traditionally produced in non-sustainable processes from fossil resources. Whole-cell biocatalysis bears great potential to provide a variety of aromatics from renewable carbon sources, thereby offering a more sustainable alternative. In this context, chorismate, the end product of the shikimate pathway, is an important biosynthetic hub compound that serves as precursor of a multitude of industrially relevant aromatics. Here, we screened several pathways for chorismate-derived bioproduction of five different mono- and dihydroxybenzoates in tyrosine-overproducing Pseudomonas taiwanensis GRC3Δ5-TYR1. Subsequently, twelve different modifications targeting the bifunctional chorismate mutase/prephenate dehydratase PheA were screened to reduce flux from chorismate to phenylalanine and tyrosine, thereby further enhancing the production of 2-hydroxy- and 2,3-dihydroxybenzoate without causing an auxotrophy. An auxotrophic ΔpheA strain served as benchmark control. Most promising modifications were subsequently also evaluated for 3-hydroxy-, 4-hydroxy- and 2,5-dihydroxybenzoate production demonstrating increased yields. Replacing the native pheA gene with the unmodified homolog from Escherichia coli was the most beneficial, enabling an increased production of up to 38.2% when combined with attTn7::P 14g -SmCH-IV. With this modification, the highest production was achieved for 4-hydroxybenzoate resulting in titers of 3.59 mM and a yield of 20.9% (Cmol/Cmol) from glucose. However, the impact of the respective pheA modification varies with the applied production module, further emphasizing the strong interplay with the production host's metabolism.
Kofler et al. (Tue,) studied this question.