Metabolic Engineering of 'Pseudomonas putida' KT2440 for the Production of 'para'-Hydroxy Benzoic Acid

'para'-Hydroxy benzoic acid (PHBA) is the key component for preparing parabens, a common preservatives in food, drugs, and personal care products, as well as high-performance bioplastics such as liquid crystal polymers. 'Pseudomonas putida' KT2440 was engineered to produce PHBA from glucose via the shikimate pathway intermediate chorismate. To obtain the PHBA production strain, chorismate lyase UbiC from 'Escherichia coli' and a feedback resistant 3-deoxy-d-arabino-heptulosonate-7-phosphate synthase encoded by gene 'aroG'D146N were overexpressed individually and simultaneously. In addition, genes related to product degradation (pobA) or competing for the precursor chorismate ('pheA' and 'trpE') were deleted from the genome. To further improve PHBA production, the glucose metabolism repressor 'hexR' was knocked out in order to increase erythrose 4-phosphate and NADPH supply. The best strain achieved a maximum titer of 1.73 g L⁻¹and a carbon yield of 18.1% (C-mol C-mol⁻¹) in a non-optimized fed-batch fermentation. This is to date the highest PHBA concentration produced by 'P. putida' using a chorismate lyase.