Biodegradation of PAHs by Acinetobacter isolated from karst groundwater in a coal-mining area

A bacterial strain Acinetobacter sp. WSD with phenanthrene-degrading ability was identified based on biochemical tests and 16S rDNA gene sequence analysis. The strain was isolated from polycyclic aromatic hydrocarbons (PAHs)-contaminated groundwater from a coal-mining area of the Guozhuang karst water system in Shanxi province of northern China. Acinetobacter sp. WSD could utilize fluorine (FLO), phenanthrene (PHE) and pyrene (PYR) as its sole carbon source and was able to degrade other PAHs. Approximately 90 % of FLO, 90 % of PHE and 50 % of PYR were degraded after 6 days’ incubation. The logistic model well fitted all the experimental data. The specific degradation rates in glucose were higher than that in HCO₃ ⁻, indicating that organic carbon source promoted the growth of Acinetobacter sp. WSD and the degradation of PAHs. In presence of humic acids (HA), the total degradation rate was accelerated, although there was a delay at the beginning. In the case of high HA concentration, co-metabolism between PAHs and HA occurred. The metabolic pathway for the three compounds of PAHs was discussed using GC–MS data. Phthalic acid was found in their metabolites. Phenol, 2,5-bis(1,1-dimethylethyl), a new type of PAHs metabolites that have been reported before was found after 2 days degradation.