Production of a biocatalyst of Pseudomonas putida CECT5279 for DBT biodesulfurization:: Influence of the operational conditions

The influence of working conditions on the growth batch of Pseudomonas putida CECT5279 has been studied, in regard to both the growth rate and the desulfurization capability accumulated in the cells. These operational conditions include pH conditions (buffered and nonbuffered media, using different carbon sources (glucose, citrate, and glutamic acid)), operating temperatures (26 - 32 degrees C), and different dissolved oxygen concentrations, due to different aeration conditions (different air flows, using enriched air, etc.). Pseudomonas putida CECT5979, which is a genetically modified microorganism (GMO), has the ability to convert dibenzothiophene (DBT) to 2-hydroxybiphenyl (HBP), desulfurizing the organic molecule. To get the best conditions to obtain desulfurizing cells, a parameter (D-BDS) that incorporates both biomass concentration and time to reach a particular percentage of desulfurizing capability (X-BDS) has been used. The optimum value of D-BDS has been obtained under the following working conditions: temperature, 30 degrees C; nonbuffered medium with glutamic acid as the carbon source; and, in relation to the dissolved oxygen concentration, the best conditions for growth are not the same as those required to get the highest desulfurizing activity. A kinetic: model based on a logistic equation has been applied to describe biomass concentration during P. putida CECT5979 growth. Kinetic model parameters (mu and C-X(max)) were obtained under several operating conditions. A model proposed in a previous work [Martin et al., Energy Fuels 2004, 18, 851-857] was applied to describe biodesulfurization capability evolution during growth. Predicted values of biomass concentration and biodesulfurizing capability percentage achieved by the cells can be obtained during bacteria growth, with values very similar to those found experimentally, in a wide interval of operating conditions.