Engineering bacterium E coli for biosynthesis of aromatics 3-hydroxybenzoic acid and L-phenylalanine

Microbial biosynthesis of aromatics has recently received increasing research interest due to its advantage in utilization of renewable feedstocks, mild bioconversion condition and strong potential for scale-up. This study investigated the biosynthesis of two aromatics 3-hydroxybenzoic acid (3HB) and L-phenylalanine (Phe) using metabolically engineered bacterium E. coli as the workhorse. Specifically, for 3-hydroxybenzoic acid, the biosynthesis pathway was designed and established in E. coli through functional expression of the selected pathway enzymes. A series of E. coli mono-cultures and E. coli-E. coli co-cultures were developed for converting renewable carbon substrate glycerol to 3HB. Optimization of the biosynthetic system resulted in the production of 294 mg/L 3HB with a yield of 0.059 g/g glycerol. For L-phenylalanine, the biosynthesis was achieved by over-expression of several key pathway enzymes. Moreover, a rationally designed cell selection system and a Phe exporter protein were adapted to boost the biosynthesis performance, which led to the production of 1060 mg/L Phe using glucose as the carbon substrate with 0.212 g/g yield. The achievements of this study offer important insights for aromatic biosynthesis in engineered microbes.