Cloning of Vitreoscilla hemoglobine in Erwinia herbicola and its effect on L-DOPA production

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 Erwinia herbicola, was investigated. The constructed recombinant bearing the VHb gene (vgb+) had substantially higher levels of cytoplasmic L-DOPA ( 97 mg L-1 for E. herbicola) than its respective host (33.8 mg L-1) and the vgb- control strain ( 35.8 mg L-1). Further, the vgb+ recombinants E. herbicola had about two orders of magnitude higher dopamine level than its host. The highest L-DOPA and dopamine levels were observed in post-stationary growth phase (24 h) of cultivation in nutrient rich medium supplemented with L-tyrosine. Similarly, TPL activity was also highest in the same cultures. 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.