Gas Chromatographic evaluation of hydrocarbon degradation capabilities of Phyllosphere-derived Bacteria in simulated bioremediation of contaminated soil

Monitoring hydrocarbon degradation is critical to assessing environmental pollution and the effectiveness of bioremediation strategies. Phyllosphere bacteria residing on plant surfaces have been shown to play a vital role in breaking down hydrocarbons; however, there is limited understanding of the compound-specific degradation patterns within the complex microbial communities present in the phyllosphere. This study evaluated the hydrocarbon-degrading capacities of four phyllosphere-derived isolates (Kocuria kristinae EN3, Pseudomonas oleovorans EP3, Pseudomonas aeruginosa EP4, and EP7) and a mixed-species consortium in comparison to natural attenuation in simulated bioremediation of contaminated soil (soil micrococosm) using Gas chromatography-flame ionization (GC-FID) analysis. Soil microcosms were amended with 5 g kg⁻¹ spent engine oil and inoculated with either individual isolates (~10⁸ CFU g⁻¹), the consortium (equal proportions of all four strains), or left uninoculated (natural attenuation). Incubation proceeded for 60 days at 28 °C under aerobic conditions. GC-FID analyzed hydrocarbon profiles at day 0 and day 60 to quantify relative peak areas and identify emergent byproducts. Results revealed that the consortium achieved a 2-fold increase in 1-Docosene (from 14.3% to 29.5% area) and produced shorter alkanes (Hexadecane, 0.20%; 1-Hexane, 0.99%). Individual strains displayed divergent patterns: EP3 eliminated mid-chain alkanes and generated halogenated byproducts (e.g., trichloromethane, 0.52%), EN3 uniquely accumulated a fluorinated ester (Octacosyl heptafluorobutyrate, 13.7%), and EP7 selectively enriched 1-Docosene (22.4%). Natural attenuation mirrored many effects of the consortium, with cyclic hydrocarbons (Cyclohexane) increasing from 0.71% to 15.2%, indicating substantial indigenous activity. In conclusion, this study highlights the efficacy of GC-FID in tracking hydrocarbon degradation and the potential of phyllosphere bacteria in bioremediation. Future research should focus on optimizing bacterial consortia for field-scale applications.