Characterization of the F-76 diesel and Jet-A aviation fuel hydrocarbon degradation profiles of Pseudomonas aeruginosa and Marinobacter hydrocarbonoclasticus

To better understand the process of fuel biodeterioration, Jet-A and F-76 diesel fuel were exposed to Pseudomonas aeruginosa, a common fuel contaminant, and Marinobacter hydrocarbonoclasticus, a marine hydrocarbon degrader, and the extent of hydrocarbon decomposition produced by these bacteria determined. Degradation assays containing fuel-minimal media mixtures and bacteria were analyzed by gas chromatography (GC) to discern the consumption of fuel hydrocarbons. Experiments were conducted in closed systems to prevent evaporation of hydrocarbons and allow accurate quantitation. Results indicated that P. aeruginosa preferred to consume mid-range normal alkanes (C12-C18) followed by higher chain n-alkanes (C19-C23). Cycloparaffins were consumed at much lower rates, while aromatic and isoparaffins were not consumed. However, M. hydrocarbonoclasticus showed a different profile with preferential degradation of shorter n-alkanes (C8-C11) and specific aromatic compounds. Both types of bacteria were incapable of degrading branched alkanes. During larger scale bioreactor tests, bacteria were able to degrade similar hydrocarbons. This study clearly demonstrated that the effects of fuel biodeterioration can go well beyond corrosion and filter fouling, with different bacteria metabolizing different fuel hydrocarbons and presenting the possibility for microbes to directly change fuel composition and properties. Results are discussed in light of the use of newer alternative fuels which can have dramatically different hydrocarbon profiles compared to conventional petroleum fuels.