Role of Native Bacteria as a Bioremediating Agent for Naphthalene and Phenanthrene

Abstract

Polycyclic Aromatic Hydrocarbons (PAH) are major contaminants of the environment, associated with common anthropogenic activities such as oil refineries and incomplete combustion of fossil fuel.Naphthalene and phenanthrene are types of simplest PAH. The existence of these pollutants in aquatic environments is toxic and dangerous for human and other organisms. The microbial populations in contaminated sites are able to degrade the stable compounds like PAH. The goal of this study is to evaluate the degradation potential of naphthalene and phenanthreneby native bacteria isolated from oil contaminated coastal water and sediments in Sri Lanka. The isolated strains were identified as Bacillus cereus, Enterobactersp. and Enterobacterludwigiiby 16s RNA.Each bacterial strain was inoculated into LB broth incorporated with PAH (1%v/v) and redox indicator (2% v/v) and incubated at room temperature (28oC) with constant shaking at 180rev/min for 14 days with control without bacterial inoculation. The degradation efficiency of strains was assessed spectrophtometrically by measuring absorbance at 609nm for the residual hydrocarbon. The results showed that the highest degradation achieved by the bacteriumBacillus cereus (73%) whilst;Enterobactersp. and E. ludwigiishowed descending trend of the naphthalene degradation at 63% and 61% respectively after 14 days of incubation. The highest degradation percentage of phenanthrene (87%) was record for E.ludwigiiwhereB.cereusand Enterobactersp.showed 86% and 79% degradation respectively. These PAH degraders identified in the present study could potential remediates for bioremediation of polluted marine environment and in oil contaminated fields in future.