Biodegradation of phenol in hypersaline conditions by Halomonas sp. strain PH2-2 isolated from saline soil

Phenolic compounds are hazardous pollutants known to be toxic at low concentration. Removal of phenols from industrial wastewater streams before their discharge into receiving water bodies is thus obligatory. Numerous phenol-degrading non-halophilic bacterial isolates have been described, but detailed information regarding phenol degradation by halophiles is rather sparse. Here we report a new phenol-degrading halophilic bacterium isolated from a hypersaline soil. The bacterium was identified as Halomonas sp. strain PH2-2 using 16S rDNA sequence analysis (GenBank accession number HM543189). Strain PH2-2 was isolated by a multistep enrichment and screening techniques on mineral medium containing 100 mg l−1 of phenol as sole source of carbon. The strain was able to utilize phenol and p-cresol as sole source of carbon and energy but not nitrophenols and chlorophenols. The bacterium was able to degrade up to 1100 mg l−1 of phenol but cell growth was inhibited at higher phenol concentrations. The strain was able to remove phenol in media containing 18% NaCl but the removal efficiency decreased from 95% to 64% in comparison to media containing 7% NaCl. The results indicated the potential application of the strain PH2-2 for treatment of hypersaline phenol-containing industrial wastewaters.