Fuel is a harsh environment for microbial growth. However, some bacteria can grow well due to their adaptive mechanisms. Our goal was to characterize the adaptations required for Pseudomonas aeruginosa proliferation in fuel. We have used DNA-microarrays and RT-PCR to characterize the transcriptional response of P. aeruginosa to fuel. Transcriptomics revealed that genes essential for medium- and long-chain n-alkane degradation including alkB1 and alkB2 were transcriptionally induced. Gas chromatography confirmed that P. aeruginosa possesses pathways to degrade different length n-alkanes, favoring the use of n-C11-18. Furthermore, a gamut of synergistic metabolic pathways, including porins, efflux pumps, biofilm formation, and iron transport, were transcriptionally regulated. Bioassays confirmed that efflux pumps and biofilm formation were required for growth in jet fuel. Furthermore, cell homeostasis appeared to be carefully maintained by the regulation of porins and efflux pumps. The Mex RND efflux pumps were required for fuel tolerance; blockage of these pumps precluded growth in fuel. This study provides a global understanding of the multiple metabolic adaptations required by bacteria for survival and proliferation in fuel-containing environments. This information can be applied to improve the fuel bioremediation properties of bacteria.

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While undesirable in aviation fuel systems, water is both ubiquitous and tenacious; thus, interactions between water and aviation turbine fuel occur regularly. From a fuel user perspective, it is important to know, understand, and be able to predict such fuel–water interactions, e.g., water solubility, water settling rate, and interfacial tension, for proper mitigation. We explore these interactions as well as surface tension of both petroleum-derived and alternative jet fuels to compare potential differences between product compositions on these physical interactions. Observations indicate a positive, nonlinear correlation between water solubility and both aromatic content and temperature (from 0 to 50 °C). Water settling rates appear to follow a Stokes’ law model; therefore, bulk chemical composition indirectly influences settling rates via density and viscosity. Finally, surface tension appears positively correlated to sample density, while interfacial tension is correlated to both surface tension and fuel aromatic content.

Oxygen consumption and deposition measurements of model fuel mixtures and real fuels are used to explore the roles that heteroatomic fuel species and their interactions play during fuel autoxidation. A range of temperatures, oxygen consumption regimes, and flow environments are employed to provide results applicable over a wide range of fuel autoxidative conditions. The quartz crystal microbalance (QCM) provides a low temperature (140 °C) batch reactor environment for long reaction times (minutes to hours) with oxygen consumption and sensitive, in situ deposition measurements. The JFTOT system provides a flowing environment at higher temperatures (260 to 300 °C) and short residence times (seconds) which is modified with both an outlet oxygen sensor and with quantitative deposition measurements via ellipsometry. These techniques are used to study model systems (Exxsol D80 with added heteroatom species) and real jet fuels to determine the role of heteroatomic species in jet fuel autoxidation and deposition. The QCM results demonstrate that nitrogen and sulfur species (e.g., indoles/anilines and sulfides) interact during jet fuel autoxidation to encourage deposit formation. The further addition of phenol species, which occur naturally in most petroleum-derived jet fuels, facilitates even greater deposit production. This behavior is confirmed in the JFTOT via addition of nitrogen and sulfur-containing species to medium and low sulfur jet fuels. These results, along with gas chromatographic (GC) analysis of samples collected during autoxidation in the QCM, show rapid sulfur autoxidation followed by a slower reaction of the nitrogen species to form deposit precursors, implying a stepwise reaction of sulfur oxidation products with nitrogen species to form deposit precursors. These results have important implications for fuel production strategies and mitigation of thermal stability degradation during fuel pipeline transport, storage, and use.

Understanding the effect of conventional and alternative fuels on the marine bacterial community is crucial, as it pertains to the impact, biodegradation, and final fate of these fuels in the environment. Metagenomics analysis demonstrated that conventional and alternative fuels promoted the growth of Proteobacteria. Marinobacter and Desulfovibrio were predominant in seawater exposed to conventional jet propellant-5 (JP-5), while Hyphomonas and Rhodovulum were most abundant in seawater with hydroprocessed renewable jet fuel (HRJ) and conventional F-76 diesel, respectively. The phyla Bacteroidetes, Firmicutes, and Lentisphaerae were underrepresented in samples with fuel, and these phyla were largely comprised of unclassified bacteria. Culture-dependent tests isolated several of the same genera detected in high abundance by metagenomics DNA sequencing, including Marinobacter, Rhodovulum, and Halobacillus. Growth studies in fuel and gas chromatography analysis demonstrated that isolates grew in fuel and metabolized hydrocarbons efficiently. The hydrocarbon degradation profile of each bacterium was conserved from conventional to alternative fuels. The study indicated that bacteria must out-compete others to get established and proliferate. Competition between hydrocarbon degraders was an important factor affecting the bioremediation process. This study provides insights into the growth characteristics of hydrocarbon-degrading bacteria and the effects of fuel on marine bacterial communities.

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Pseudomonas frederiksbergensis strain SI8 is a psychrotrophic bacterium capable of efficient aerobic degradation of aromatic hydrocarbons. The draft genome of P. frederiksbergensis SI8 is 6.57 Mb in size, with 5,904 coding sequences and 60.5% G+C content. The isopropylbenzene (cumene) degradation pathway is predicted to be present in P. frederiksbergensis SI8.