Production of L-DOPA and dopamine in recombinant bacteria bearing the Vitreoscilla hemoglobin gene

Given the well-established beneficial effects of Vitreoscilla hemoglobin (VHb) on heterologous organisms, the potential of this protein for the production of L -DOPA and dopamine in two bacteria, Citrobacter freundii and Erwinia herbicola, was investigated. The constructed recombinants bearing the VHb gene (vgb⁺) had substantially higher levels of cytoplasmic L -DOPA (112 mg/L for C. freundii and 97 mg/L for E. herbicola) than their respective hosts (30.4 and 33.8 mg/L) and the vgb^– control strains (35.6 and 35.8 mg/L). Further, the vgb⁺ recombinants of C. freundii and E. herbicola had 20-fold and about two orders of magnitude higher dopamine levels than their hosts, repectively. The activity of tyrosine phenol-lyase, the enzyme converting L -tyrosine to L -DOPA, was well-correlated to cytoplasmic L -DOPA levels. As cultures aged, higher tyrosine phenol-lyase activity of the vgb⁺ strains was more apparent.