Air Force

Rapid detection of bio-contamination in fuel tanks

Accurate and quantitative real-time detection of microbial growth in fuel in the field before high cell density is reached

Energy Sensors

The detection of bio-contamination in a jet fuel sample from a fuel tank. (a) The aqueous phase of a contaminated Jet A fuel sample. After centrifugation, the supernatant was removed and the cell pellet was labeled with 1.5 μM of peptide-QD545-peptide (or QD alone) in PBS. The labeled cell pellet was re-suspended in 0.5 mL of PBS, and the fluorescence was measured (c). The sample was serially diluted and plated to determine CFUs (b).

Bio-contamination can cause a myriad of problems in a fuel system including, hydrocarbon degradation, changes in fuel properties and quality, corrosion, filter clogging, deactivation of fuel-water coalescers, coating degradation, inaccurate fuel level readings, decreased vehicle performance.

Early detection of biofouling enables the use of cost-effective mitigation strategies that may reduce the contamination’s impact on the fuel system. An early warning detection sensor to alert maintenance crew of bio-contamination could save millions of dollars per year in repair costs over the lifetime of the vehicle and fuel system.

To date, there has been no simple and reliable method for detecting microbes and bio-deterioration in fuel. The methods used today are typically performed by highly trained scientists in laboratories equipped with molecular-based instrumentation that are quantitative in nature and do not differentiate between living and non-living microbes. While more straightforward colony counting methods are quantitative and do not require expensive instrumentation this approach is time-consuming and only capable of detecting culturable bacteria, which may represent just 10% of all bacteria present within a fuel system.

Commercially-available detection kits are available, but are also cumbersome, inaccurate, and, at best, semi-quantitative. Some of these kits require long culture growth for visual analysis or quantification of Adenosine Triphosphate (ATP). However, ATP levels are highly dependent on the growth stage of the organism. Other commercially-available kits use antibody-based detection methods which are affected by degradation and are negatively influenced by the presence of fuel.

Air Force scientists are using broad-range peptide biorecognition elements (BREs) that target cell surface determinants produced by hydrocarbon-degrading microorganisms during growth in fuel. The BREs are cross-linked to quantum dots and a reporter molecule that can generate a chemiluminescent, fluorescent, colorimetric or transducing nanomaterial signal. BREs provide several benefits over other molecular probes, such as high chemical diversity, ease of synthesis and conjugation to the surface of a signal transducer, and high stability in harsh environments, such as fuel.

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