Enhancement of  l‐phenylalanine production in Escherichia coli by heterologous expression of Vitreoscilla hemoglobin.

Abstract: l‐Phenylalanine is an important amino acid that is widely used in the production of food flavors and pharmaceuticals. Generally, l‐phenylalanine production by engineered Escherichia coli requires a high rate of oxygen supply. However, the coexpression of Vitreoscilla hemoglobin gene (vgb), driven bya tac promoter, with the genes encoding 3‐deoxy‐ d‐arabinoheptulosonate‐7‐phosphate synthetase (aroF) and feedback‐resistant chorismate mutase/prephenate dehydratase (pheA^fbr), led to increased productivity and decreased demand for aeration by E. coli CICC10245. Shake‐flask studies showed that vgb‐expressing strains displayed higher rates of oxygen uptake, and l‐phenylalanine production under standard aeration conditions was increased. In the aerobic fermentation process, cell growth, l‐phenylalanine production, and glucose consumption by the recombinant E. coli strain PAPV, which harbored aroF, pheA^fbr, and tac‐vgb genes, were increased compared to that in the strain harboring only aroF and pheA^fbr (E. coli strain PAP), especially under oxygen‐limited conditions. The vgb‐expressing strain PAPV produced 21.9% more biomass and 16.6% more l‐phenylalanine, while consuming only approximately 5% more glucose after 48 H of fermentation. This study demonstrates a method to enhance the l‐phenylalanine production by E. coli using less intensive and thus more economical aeration conditions. [ABSTRACT FROM AUTHOR]