Optimization of pH for L-Dopa production in bench-top scale stirred-tank bioreactor using a Paraboeremia strain

Abstract

Biosimilars contain active molecules from a biological source, have the same biological function but come from a manufacturing process which differs from the traditional chemical production synthesis of the original drug, their active principles are usually more complex than those of the chemically synthesized counterparts, and only living organisms can reproduce this complexity. Parkinson is a disease associated with dopamine deficiency and levodopa has been the elected drug to treat it for decades. In recent years, various advances have allowed understanding the mechanisms of action. With chemically synthesized levodopa, patients develop motor complications manifested by the decrease in duration effect, which could be avoided with the use of microbiologically synthesized L-Dopa. The objective of this work was to study the influence of initial pH in the L-Dopa microbiological production process, by means of the operation of a bench-top bioreactor, using the selected fungus Paraboeremia LY 38.7, isolated from Las Yungas Tucumanas. For the production of L-Dopa at bioreactor scale and to study the effect of initial pH, previously optimized conditions at smaller scale were used as starting point. Accordingly, the initial pH was varied between 5.0 and 7.5, keeping constant further operative conditions for 5 days, i.e. aeration (1 vvm), temperature (25 ° C) and stirring rate (200 rpm), and sampling twice a day. Production of L-Dopa and L-Tyrosine consumption were measured by means of the Arnow method, tyrosinase monophenolase and diphenolase activities according to the dopachrome method, biomass by dry weight estimation and pH with a pHmeter. Results showed that volumetric productivity of L-Dopa was higher at pH 7 and 7.5 (4,11 mg?L-1?h-1 and 3,65 mg?L-1?h-1 respectively). These optimal pH values represented favourable conditions from the operational point of view, taking into account that recently prepared culture medium has a pH of 7.5. Additionally, it is also convenient in terms of productivity, since maximal L-Dopa production is achieved one day earlier (48 instead of 72 h) than at pH 5.0, 5.5, 6.0 and 6.5, which implies lower operating costs and adds more economic and industrial attractiveness.