Biodegradation of Phenanthrene Polluted Soil through Native Strains in the Darkhouvin Oil Field

Abstract

As a resistant and toxic polycyclic aromatic hydrocarbon (PAHs), phenanthrene is largely distributed in aquatic and terrestrial environments with adverse biological consequences. Mineralization of this toxic component via bioremediation has been vastly studied in recent years and might lead to new hope in the economic clean-up of this contaminant. The aim of this study was the isolation and identification of phenanthrene degrading bacteria from petroleum polluted environments and the assessment of their growth kinetics. Soil samples were collected from the oil-polluted sites of Darkhouvin oilfield, Iran. Bacterial isolates capable of degrading phenanthrene were characterized genetically and morphologically. Optimal level of environmental parameters including pH, time, temperature, nitrogen and phosphate source, and phenanthrene concentration were determined using Taguchi method. The results showed that different bacterial genera were isolated in which Bacillus mojavensis and Lysinibacillus sphaericus were identified as phenanthrene degrading isolates. Isolated strains showed hemolytic activity and deceased surface tension values. The optimal condition was determined as 45 °C, pH 7, nitrate 1 µg/mL, sodium phosphate 0.3 µg/mL, and on the fifth day of culturing for B. mojavensis, which showed prominent activity in phenanthrene biodegradation. In this study, the ability of native strains on the biodegradation of phenanthrene in soil was investigated. The findings suggest that isolated biosurfactant generating bacteria could biodegrade phenanthrene in optimum conditions.