Relation between bacterial strain resistance to solvents and biodesulfurization activity in organic medium.

Microorganisms used in biodesulfurization of petroleum products have to withstand high concentrations of hydrocarbons. The capacities of seven desulfurizing strains of Rhodococcus to be active in the presence of solvents were evaluated. Octanol and toluene (log P=2.9) were selected as toxic solvents. The effect of the solvents was determined by measuring either inhibition of growth or the decrease in respiratory activity of the cells. Differences among strains in their resistance to solvent responses were observed, but these variations were dependent on the test used. Resistance to solvents was then compared to the capacity of the different strains to retain biodesulfurization activity in the presence of hexadecane. Inhibition of desulfurization by high concentrations of hexadecane was found to be well correlated to the sensitivity of the strains to respiration inhibition by toluene, but not to growth inhibition. This result also showed that the respirometric test was a rapid and reliable test to select solvent-resistant strains for use as resting cells in biocatalysis processes, such as biodesulfurization, in organic media.