Biological removal of crude oil with the use of native bacterial consortia isolated from the shorelines of the Caspian Sea

Abstract

This study was aimed at investigating the possibility of biological removal of crude oil with the use of native bacterial strains, isolated from the shorelines of the Caspian Sea. For this purpose, based on the growth rate, hemolytic and emulsification activity, oil spreading assay and liquid surface tension reduction, 115 bacterial strains were isolated from seven selected stations across the shorelines of the Caspian Sea. Among them, 15 isolates were selected for further analyses. Three isolates (J3, J5 and J12) showed the highest efficiency for crude oil removal. Based on the sequence of 16S rRNA gene, the isolates were identified as Bacillus cereus (J3), Staphylococcus haemolyticus (J5) and Pseudomonas aeruginosa (J12). The results showed that isolate J3 had a better ability to degrade short (C9–C13) and medium length (C13–C25) in comparison with the long length (C32–C35) of n-alkanes in the crude oil residues. The total petroleum hydrocarbon (TPH) reduction by the B. cereus (J3) isolate was about 88.8 (mg g−1). It can be concluded that about 60% of n-alkanes in crude oil residues were removed. Also, the TPH reduction for S. haemolyticus (J5) and P. aeruginosa (J12) isolates were about 123.6 and 113.2 (mg g−1), respectively, so these strains could reduce the TPH about 55% and 50%, respectively. The TPH reduction in consortia containing B. cereus, S. haemolyticus and P. aeruginosa was about 18.3 (mg g −1), 83% of crude oil residues (1%, v/v) in 22 days.