Bioaugmentation of diesel-contaminated soil with Pseudomonas sp. DTF1

To bioaugment contaminated soil, the behavior of inoculated microorganisms in the soil must first be understood. In this study, Pseudomonas sp. DTF1, a diesel-degrading bacterium, was isolated from the rhizosphere of tall fescue (Festuca arundinacea) to investigate its diesel-degrading properties in aqueous and soil environments. In an aqueous environment, Pseudomonas sp. DTF1 degraded diesel at a rate of 7309–7882 mg L⁻¹·d⁻¹ for 10,000–30,000 mg diesel L⁻¹. Pseudomonas sp. DTF1 efficiently degraded high-weight alkanes with 20–26 carbons in diesel, and the DTF1 strain could also utilize lubricant oil and pyrene. More specifically, this bacterium can produce biosurfactants, and its alkB gene was associated with the degradation of diesel. By inoculating Pseudomonas sp. DTF1 into diesel-contaminated soil, the diesel removal efficiency was increased from 15% (without inoculation) to 55% in 14 days. Although there was no significant difference in the 16S rRNA gene copy numbers, which represent bacterial abundance, the relative alkB gene copy numbers of the soil inoculated with the DTF1 strain were 4.7–9.5 times higher than those of the soil without inoculated microorganisms. Additionally, the relative abundance of Pseudomonas was over 60% in the soil inoculated with Pseudomonas sp. DTF1. The results suggest that Pseudomonas sp. DTF1 contributed significantly to diesel degradation during bioaugmentation by increasing the alkB gene abundance of the soil microorganism community.