Biodegradation of Phenanthrene and Heavy Metal Removal by Acid-Tolerant Burkholderia fungorum FM-2

Abstract

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.

Keywords: Burkholderia fungorum; acid-tolerant bacteria; bioremediation; heavy metal resistance; phenanthrene biodegradation.

Figure 1

Effect of initial concentration of PHE (300–600 mg L⁻¹) on a degradation rate and OD₆₀₀ by strain FM-2.

Figure 2

Effect of incubation time on PHE degradation at 25°C under shaking conditions (200 rpm) within 72 h.

Figure 3

Growth of bacteria and degradation rate at different temperature.

Figure 4

The ability of strain FM-2 to tolerate various salinities.

Figure 5

Effect of different pH at 25°C under shaking conditions of 200 rpm.

Figure 6

Effect of heavy metals on PHE degradation within 7 d (A), Zn (II) and Cd (II); (B), Pb (II).

Figure 7

Accumulation of heavy metals in FM-2 (A, cell wall; B, intracellular space).

Figure 8

PHE residual rate (%) in co-contaminated soil (all soils had a concentration of PHE 150 mg kg⁻¹ dry soil on day zero) (Treatment 1, sterilized soil + PHE; Treatment 2, sterilized soil + PHE + FM-2; Treatment 3, sterilized soil + PHE + Cd (II) + FM-2; Treatment 4, sterilized soil + PHE + Zn (II) + FM-2).