Modeling the production of a Rhodococcus erythropolis IGTS8 biocatalyst for DBT biodesulfurization:: Influence of media composition

The production of a biocatalyst of Rhodococcus erythropolis IGTS8 able to desulfurize dibenzothiophene (DBT) has been studied. Biomass growth rate and the development of removing sulfur capability during microorganism growth have been measured and modeled. Different growth media have been employed, different carbon (glucose, glutamic acid and citrate), nitrogen (ammonium and/or glutamic acid) and sulfur (DBT), dimethylsulfoxide (DMSO) and magnesium sulphate-sources have been used, as well as different DMSO concentrations (1300, 500, 250 and 50 mu M), in order to study its influence on growth rate and desulfurizing capability. Experimental results show clear differences both in growth and in the biodesulfurization capability developed by cells depending on the media composition. To quantify the desulfurization capability a parameter has been defined: DBDS, biodesulfurization degree developed during growth, useful not only to compare the results achieved under different media and conditions but also to compare different microorganisms with desulfurization capability. Inside the experimental range studied, the best production media is composed of 20 g L-1 glucose, using 670 ppm. NH4+ and 1300 mu M DMSO as carbon, nitrogen and sulfur sources. A non-structured kinetic model to describe growth and desulfurizing capability development is proposed and applied by non-linear simpleresponse fitting to all the experiments carried out. The model is able to describe all the experimental data with good statistical parameters. (c) 2005 Elsevier Inc. All rights reserved.