Construction of an l-phenylalanine-producing tyrosine-prototrophic Escherichia coli strain using tyrA ssrA-like tagged alleles

To construct a Phe-producing Tyr⁺ Escherichia coli strain, TyrA (chorismate mutase/prephenate dehydrogenase) activity was varied by engineering a proteolytically unstable protein. The tyrA in the E. coli BW25113 was altered to include ssrA-like tags. The tagged tyrA genes, which ensured different growth rates in M9 medium, were introduced into a Phe-producing strain to replace ΔtyrA. Strains with unstable TyrA-(A)ANDENYALAA proteins had a lower biomass yield and a higher Phe accumulation than strains generating the more stable TyrA-(A)ANDENYALDD. The Tyr/Phe ratio produced by the TyrA-tag strains was 10-fold less than that produced by the TyrA^wt strain.