Biodegradation of phenanthrene as a model hydrocarbon: Power display of a super-hydrophobic halotolerant enriched culture derived from a saline-sodic soil

In this study, after evaluating the degradation activity of enriched cultures from four crude oil-contaminated soils in mineral salt medium, the most efficient ones were selected for further studies. The chemical analysis of cell-free extract containing phenanthrene by HPLC suggested the superior enriched culture was able to degrade 87.66% of phenanthrene at the concentration of 40 mg L-1 within 10 days. This experiment was done under optimal conditions (37 °C, 10% salinity, and pH around 7 to 7.5). The 16S rRNA sequencing of isolates from this superior enriched culture indicated the highest similarity to Acidovorax delafieldii (Q-SH3), Bacillus hwajinpoensis (Q-SH12), and Bacillus rhizosphaerae (Q-SH14). After biodegradation of phenanthrene in liquid medium, the extracts were analyzed to measure barley and alfalfa germination. Results showed a lower level of toxicity to the seeds, hence this enriched culture could be used for bioremediation of saline environments contaminated by phenanthrene and other similar compounds.