Identification of Pseudomonas protegens and Bacillus subtilis Antimicrobials for Mitigation of Fuel Biocontamination

Hydrocarbon fuel biofouling and biocorrosion requires expensive cleanup of aviation infrastructures unless appropriate sustainment measures are applied. Alternative to current chemical biocides used in fuel sustainment, the identification of novel biological control agents offers promising alternatives. In this study, 493 microbial fuel isolates from our in-house repository were screened to identify new endogenously produced antimicrobial compounds. Using agar plug screening, liquid culture growth testing, and Jet A fuel culture assays, the two fuel isolate strains Pseudomonas protegens #133, and Bacillus subtilis # 232 demonstrated promising biocontrol activity against bacteria, yeast and filamentous fungi. Mass spectrometry analysis (LC-MS/MS) of #232 culture filtrate identified several common lipopeptide antimicrobials including gageostatin C, gageopeptin B, and miscellaneous macrolactins. In contrast, LC-MS/MS identified the siderophore pyochelin as one of the predominant compounds in #133 culture filtrate with previously demonstrated antimicrobial effect. Jet fuel microbial consortium culture testing of #133 culture filtrate including flow-cytometry live/dead cell mechanism determination demonstrated antimicrobial action against Gram-positive Gordonia sp. bacteria. The study concludes that antimicrobial compounds secreted by #133 have bactericidal effect against Gordonia sp. and cause cell death through bacterial lysis and membrane damage with potential applications in biocidal treatment of hydrocarbon-based aviation fuels.