A diesel spill can remain in soil for years. This study found that the strongest cleanup came not from one microbe, but from a carefully matched team of fungi and bacteria working together. Even a decade after the release of these contaminants, residual concentrations of numerous pollutants remained in the soil, along with significantly elevated levels of other petroleum chemicals.

Some chemicals exceeded recommended soil limits, while reference values for some types of pollutants were not covered by the guidelines. The study aimed to develop microbial consortia with potential for cleaning petroleum hydrocarbons from contaminated environments.

Fungal and bacterial strains were isolated from areas contaminated with diesel and biodiesel, then different combinations were designed using their chemical activity and compatibility. These combinations and individual strains were tested for their ability to break down diesel oil, and the partnerships showed effective targeting and breakdown of complex pollutants.

The selected bacterial and fungal strains were examined together to see how they grew when co-cultivated. The goal was to formulate microbial consortia capable of degrading petroleum hydrocarbons. The central idea is like assembling a repair crew: one worker may handle one part of a damaged house, but several workers with different skills can tackle more of the job together.

Here, microbial consortia degraded diesel pollutants more effectively than isolated strains. The microorganisms were selected from contaminated soil, where native species had already been exposed to diesel and biodiesel. The study identified fungi and bacteria, then looked for chemical activities that could help them act on the pollutants.

The degradation rates differed greatly between treatments after incubation, showing that the choice of strain or consortium mattered. When two bacterial strains were combined, they achieved higher degradation of total pollutants than either strain alone and improved removal of several hydrocarbons.

The best mixed fungal–bacterial consortium degraded every analyzed PAH at rates of at least ninety-one percent, indicating a broad spectrum of degraded compounds. This consortium included a fungus and two bacteria, and it achieved the best results among the tested groups.

The results showed a significant contrast between strains tested separately and their use in consortia, suggesting that cooperation between strains was essential for degrading many hydrocarbon components. The combined action of different microbial species can improve degradation efficiency and expand the range of compounds that microbes can act on.

The best consortium removed ninety-three point six one percent of total PAHs and ninety-three point five two percent of total petroleum hydrocarbons measured in diesel oil. The results indicate that combining microbial species with different ways of acting can greatly improve hydrocarbon degradation compared with isolated strains.

Future research should test and improve these consortia in contaminated soil to understand how well they work in different environments. The best microbial team removed more than ninety percent of the measured pollutants in the laboratory.

That suggests future cleanup could use communities of microbes, rather than relying on a single strain.