Phenanthrene (PHE) is a common pollutant of acidic and non-acidic environments that is recalcitrant to biodegradation. Herein, Burkholderia fungorum FM-2 (GenBank accession no. KM263605) was isolated from oil-contaminated soil in Xinjiang and characterized morphologically, physiologically, and phylogenetically. Environmental parameters including PHE concentration, pH, temperature, and salinity were optimized, and heavy metal tolerance was investigated. The MIC of strain FM-2 tolerant to Pb(II) and Cd(II) was 50 and 400 mg L⁻¹, respectively, while the MIC of Zn(II) was >1,200 mg L⁻¹. Atypically for a B. fungorum strain, FM-2 utilized PHE (300 mg L⁻¹) as a sole carbon source over a wide pH range (between pH 3 and 9). PHE and heavy metal metabolism were assessed using gas chromatography (GC), inductively coupled plasma optical emission spectroscopy (ICP-OES), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), Fourier-transform infrared (FTIR) spectroscopy and ultraviolet (UV) absorption spectrometry. The effects of heavy metals on the bioremediation of PHE in soil were investigated, and the findings suggest that FM-2 has potential for combined bioremediation of soils co-contaminated with PHE and heavy metals.

In this study, the Pb²⁺ biosorption potential of live and dead biosorbents of the hydrocarbon-degrading strain Rhodococcus sp. HX-2 was analyzed. Optimal biosorption conditions were determined via single factor optimization, which were as follows: temperature, 25°C; pH, 5.0, and biosorbent dose, 0.75 g L⁻¹. A response surface software (Design Expert 10.0) was used to analyze optimal biosorption conditions. The biosorption data for live and dead biosorbents were suitable for the Freundlich model at a Pb²⁺ concentration of 200 mg L⁻¹. At this same concentration, the maximum biosorption capacity was 88.74 mg g⁻¹ (0.428 mmol g⁻¹) for live biosorbents and 125.5 mg g⁻¹ (0.606 mmol g⁻¹) for dead biosorbents. Moreover, in comparison with the pseudo-first-order model, the pseudo-second-order model seemed better to depict the biosorption process. Dead biosorbents seemed to have lower binding strength than live biosorbents, showing a higher desorption capacity at pH 1.0. The order of influence of competitive metal ions on Pb²⁺ adsorption was Cu²⁺ > Cd²⁺ > Ni⁺. Fourier-transform infrared spectroscopy analyses revealed that several functional groups were involved in the biosorption process of dead biosorbents. Scanning electron microscopy showed that Pb²⁺ attached to the surface of dead biosorbents more readily than on the surface of live biosorbents, whereas transmission electron microscopy confirmed the transfer of biosorbed Pb²⁺ into the cells in the case of both live and dead biosorbents. It can thus be concluded that dead biosorbents are better than live biosorbents for Pb²⁺ biosorption, and they can accordingly be used for wastewater treatment.

The demand to repair areas contaminated with hydrocarbon products has led to the development of new technologies for the treatment of contaminants in an unconventional method, that is, no physical or chemical methods are used. Biosurfactants are amphiphilic biomolecules produced by microorganisms that can be used in environments contaminated by petroleum products due to their unexceptionable tensile properties. Petroleum degrading strain Rhodococcus erythropolis HX-2 was found to be an effective producer of biosurfactants. The resulting biosurfactant (named NK) exhibits high physicochemical properties in terms of surface activity. It is capable of reducing surface tension from 54.99 to 28.89 mN/m and critical micelle concentration (CMC) is 100 mg/L. NK was found to be a substitute for chemically synthesized surfactants because of its higher solubilization efficiency for petroleum and polycyclic aromatic hydrocarbons, superior to SDS, Tween 80, Triton X-100 and Rhamnolipid (a wide used biosurfactant). In addition, it exhibits favorable emulsion stability over a wide range of pH (3–10), temperature (20–100 °C) and salinity ranges (5–20 g/L). It was found that the addition of biosurfactant can improve the efficiency of petroleum degradation, therefore it has potential applications in bioremediation.