Production of a biocatalyst of Pseudomonas putida CECT5279 for dibenzothiophene (DBT) biodesulfurization for different media compositions

The production of a biocatalyst of a genetically modified microorganism (GMO) (Pseudomonas putida CECT5279) that can desulfurize dibenzothiophene (DBT) has been studied. The biomass growth rate and the development of the sulfur-removal capability during microorganism growth have been measured and modeled. Different growth media and different carbon-glucose, carbon-citrate, and carbon-glutamic acid sources, as well as different nitrogen-ammonium and/or nitrogen-glutamic acid sources, have been used, in addition to different glutamic acid concentrations (5, 10, 20, and 40 g/L), to study their influence on the growth rate and desulfurizing capability. Experimental results show clear differences both in growth and in the biodesulfurization capability developed by the cells, depending on the media composition. To quantify the desulfurization capability, a parameter has been defined: DBDS, which is the degree of biodesulfurization developed during growth. This parameter is useful not only to compare the results achieved under different media and conditions but also to compare different microorganisms, in regard to the desulfurization capability. Inside the experimental range studied, the best production media is composed of 20 g/L of glutamic acid, with 670 ppm of NH4+ as the respective carbon and nitrogen sources. A nonstructured kinetic model that describes the growth and desulfurizing capability development is proposed and applied by nonlinear simple response fitting to all the experiments that have been performed. The model can be used to describe all the experimental data with good statistical parameters.