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.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.