A high-efficiency phenanthrene-degrading Diaphorobacter sp. isolated from PAH-contaminated river sediment

Polycyclic aromatic hydrocarbons (PAHs) are typical persistent organic pollutants that accumulate in the environment, mainly from anthropogenic activities. Microbial degradation is the main pathway of PAHs degradation in the natural environment. Therefore, the widen of the available bank of microbial resources and exploration of the molecular degradation mechanisms of PAHs are crucial to the proper management of PAHs-polluted sites. In this work, a bacterial strain, YM-6, which has a high ability to utilize phenanthrene (PHE) as its sole source of carbon and energy, was isolated from sediment contaminated with PAHs. The strain YM-6 was found to degrade 96.3% of 100 mg/L of PHE in liquid cultures within 52 h. The strain was identified as Diaphorobacter sp. by 16S rDNA sequencing. The optimum growth conditions of the YM-6 strain were studied, and the results indicated that the optimum growth temperature of the strain was 30 °C, and the optimum growth pH was 7. The stain is well-suited for high-temperature stress (40 °C), and it could withstand 400 mg/L of PHE. The strain's PHE metabolism was assayed using GC-MS analyses. The results revealed that the YM-6 strain metabolized PHE via the phthalic acid pathway because the intermediates, such as phthalic acid, diethyl ester and phthalaldehydic acid, methyl ester, were detected. The use of this strain may be an attractive alternative for the bioremediation of polycyclic aromatic hydrocarbons in an aquatic environment.