Simultaneous biosynthesis of L-dopa and dopamine using recombinant microorganisms

In the study, gram-negative bacterium as Citrobacter freundii (NRRL B-2643), Erwinia herbicola (NRRL B-3466) and their recombinant culture include (vgb+/vgb-) gene (Citrobacter freundii pMK57, Citrobacter freundii pMK79, Erwinia herbicola pUC8, Erwinia herbicola pUC8:15) were used. The biosynthesis of extracellular and cytoplasmic L-DOPA and Dopamine in synthetic fermentation media by wild and recombinant cultures as comparative studied. The research focused on the improvement of L-DOPA and Dopamine level using both of recombinant DNA technology and metabolic engineering application. Experiments were carried out in 250 ml shake-flask as well as 1.0 L bioreactor. In the study, the effect of carbon source (glucose), organic (peptone, yeast extract, urea) and inorganic ((NH4)2SO4, NaNO3) nitrogen sources and their concentrations, and other medium components (NaCl and CaCl2), inoculum, pH of initial media, temperature and shaking speed on production L-DOPA and Dopamine were investigated in synthetic media for microorganisms. Mass transfer characteristics of fermentation broth in batch bioreactor were investigated. Increases in both the agitation rate and the air feed rate increased volumetric mass transfer coefficients, kLa and oxygen uptake rates, ro values. The fermentation kinetics of L-DOPA by Citrobacter freundii (NRRL B-2643) were studied in a batch system. This study focuses on comparing different kinetic models in literature and the use of artificial neural networks model. Various kinetic parameters were obtained for L-DOPA fermentation optimising with Genetic Algorithm Toolbox. The experimental results of growth, L-DOPA production and glucose consumption are compared model results, and artificial neural networks model appeared to provide a reasonable description. Key Words: L-DOPA, Dopamine, Citrobacter freundii (NRRL B-2643), Citrobacter freundii pMK57, Citrobacter freundii pMK79, Erwinia herbicola (NRRL B-3466), Erwinia herbicola pUC8, Erwinia herbicola pUC8:15, Recombinant DNA technology, Submerged fermentation, Bioprocess conditions, Batch fermentation, Bioreactor operating parameters, Kinetic modeling, Genetic algorithm, Artificial neural network modeling.