Enhanced l-phenylalanine biosynthesis by co-expression of pheAfbr and aroFwt

A β-2-thienylalanine-resistant E. coli K12 mutant carrying a Thr326Pro mutation in the regulation (R) domain of pheA (pheAfbr) was obtained by N-methyl-N′-nitro-N-nitrosoguanidine (NTG) mutagenesis. In the presence of 200 mM l-phenylalanine (l-Phe), a recombinant E. coli WSH-Z06 (pAP-B03) carrying pheAfbr as well as wild-type aroF (aroFwt) exhibited more than 70% of the chorismate mutase-prephenate dehydratase (CM–PDT) activity as observed in the absence of this amino acid. The l-Phe titer of WSH-Z06 (pAP-B03) reached 35.38 g/L in a 3-L fermentor, which was 2.81-fold higher than that of the original strain E. coli WSH-Z06. Furthermore, the l-Phe yield on glucose of WSH-Z06 (pAP-B03) (0.26 mol/mol) was twice that of E. coli WSH-Z06. This recombinant E. coli WSH-Z06 (pAP-B03) is a potential strain for over-production of l-Phe.