Production of p-Aminobenzoic acid by metabolically engineered Escherichia coli

The production of chemical compounds from renewable resources is an important issue in building a sustainable society. In this study, Escherichia coli was metabolically engineered by introducing T7lac promoter-controlled aroF(fbr), pabA, pabB, and pabC genes into the chromosome to overproduce para-aminobenzoic acid (PABA) from glucose. Elevating the copy number of chromosomal P-T7lac-pabA-pabB distinctly increased the PABA titer, indicating that elevation of 4-amino-4-deoxychorismic acid synthesis is a significant factor in PABA production. The introduction of a counterpart derived from Corynebacterium efficiens, pabAB (ce), encoding a fused PabA and PabB protein, resulted in a considerable increase in the PABA titer. The introduction of more than two copies of P-T7lac-pabAB (ce-mod), a codon-optimized pabAB (ce), into the chromosome of a strain that simultaneously overexpressed aroF(fbr) and pabC resulted in 5.1 mM PABA from 55.6 mM glucose (yield 9.2%). The generated strain produced 35 mM (4.8 g L-1) PABA from 167 mM glucose (yield 21.0%) in fed-batch culture.