Bacterial sulfate production by biodesulfurization of aromatic hydrocarbons, determined by ion chromatography

The use of bacteria to remove sulfur from crude oil or petroleum distillates is a novel concept that presents an alternative biotechnology to the current technology of hydrodesulfurization (HDS). Sulfur must be removed from crude oils prior use. The burning of fossil fuels containing sulfur releases sulfur dioxide into the atmosphere causing acid rain. The aim of this work is to determine the sulfate concentration by ion chromatography (IC), and calculate the percentage of transformation of organic bound sulfur, that is converted to sulfate, and estimate the efficiency of bacteria in desulfurization. IC is a suitable method for sulfate concentration determination. However, when chloride concentrations are significantly high, interference of the sulfate signal does occur. In this case, it could be avoided by diluting samples. A Dionex Model 2000i/SP IC system, with an anionic pre-column (Dionex AG4A), an anion separator column (Dionex AS4A), a suppressor column (Dionex AMMS-II), and a conductivity detector was used. The eluent (21 mM NaOH) and regenerant (electrolyzed 18 M omega/cm water) flow-rates were 1.0 and 2.0 ml/min, respectively. The sample loop volume was 10 microliters and the conductivity sensitivity was 30 muS. The diluted samples were filtered through a 0.45-micron filter before injection. The highest sulfate concentration detected was 24.10 mg/l, corresponding to a maximal conversion rate of 10% in a month. Sulfate ions were not detected in control samples. The correlation coefficient for a linear least squares fit was 0.99 (p < 0.001). The minimal concentration that we can read was 0.02 mg/l and this concentration corresponded to the limit of detection obtained under the conditions employed in this study. IC is an economical, sensitive and accurate way to estimate the sulfate concentrations in microbiological samples.