Novel Bacterial Strains Pseudomonas sp. and Bacillus sp. Isolated from Petroleum Oil Contaminated Soils for Degradation of Flourene and Phenanthrene

Abstract

Flourene and phenanthrene are organic compounds with high hydrophobicity and toxicity. Being recalcitrant in nature they are accumulating in the environment at an alarming concentration, posing serious threat to living beings. Thus in the present study, microorganisms were screened for their ability to degrade these contaminants at high concentrations in least period of time. Two out of fifteen isolates screened showed growth in basal medium containing 25 mg/l of fluorene/phenanthrene as the only carbon source. These selected isolates were acclimatised with step wise increased concentrations of flourene/phenanthrene for 165 days in basal medium. The acclimatised strains were identified and characterised on the basis of their morphological and biochemical characteristics and 16S rRNA gene sequence analysis. Results showed close relatedness of the isolates to Pseudomonas aeruginosa sp. and Bacillus safensis sp. Biodegradation studies carried out with these acclimatised strains at optimum conditions (pH 7 and temperature 30°C) showed 62.44% degradation of fluorene and 54.21% of phenanthrene in 10 days by Pseudomonas sp. VB92, whereas, Bacillus sp. JK17 degraded 43.64% of fluorene and 59.91% of phenanthrene in 12 days, at an initial concentration of 200 mg/l, as determined by HPTLC. During fluorene degradation by Pseudomonas sp. VB92, one metabolite was identified as fluorene,1,4-dihydro. An anionic biosurfactant (emulsification index of 80%) produced by strain VB92 during growth with PAHs, improved its degradation rate. This showed strong potential of the acclimatised strains for bioremediation and reclamation of polyaromatic hydrocarbon contaminated sites.