Biodegradation of Tapis blended crude oil in marine sediment by a consortium of symbiotic bacteria

Biodegradation rate and the high molecular weight hydrocarbons are among the important concerns for bioremediation of crude oil. Inoculation of a non-oil-degrading bacterium as supplementary bacteria increased oil biodegradation from 57.1% to 63.0% after 10 days of incubation. Both the oil-degrading bacteria and the non-oil-degrading bacteria were isolated from Malaysian marine environment. Based on the 16S rDNA sequences, the oil-degrading bacteria was identified as Pseudomonas pseudoalcaligenes (99% similarity) while the non-oil-degrading bacterium was Erythrobacter citreus (99% similarity). E. citreus does not grow on crude oil enriched medium under present experimental condition but it withstands 5000 mg kg−1Tapis blended crude oil in sediment. Under optimal condition, the oil-degrading bacterium; P. pseudoalcaligenes, alone utilized 583.3 ± 3.8 mg kg−1 (57.1%) at the rate of 3.97 × 10−10 mg kg−1 cell−1 day−1Tapis blended crude oil from 1000 mg kg−1 oil-contaminated sediment. Inoculation of E. citreus as the supplementary bacteria to P. pseudoalcaligenes enhanced biodegradation. The bacterial consortium degraded 675.8 ± 18.5 mg kg−1 (63.0%) Tapis blended crude oil from the 1000 mg kg−1 oil-contaminated sediment. Biodegradation rate of the bacterial consortium increased significantly to 4.59 × 10−10 mg kg−1 cell−1 day−1 (p = 0.02). Improvement of the oil degradation by the bacterial consortium was due to the synergetic reaction among the bacterial inoculants. There are two implications: (1) E. citreus may have a role in removing self-growth-inhibiting compounds of P. pseudoalcaligens. (2) P. pseudoalcaligenes degraded Tapis blended crude oil while E. citreus competes for the partially degraded hydrocarbons by P. pseudoalcaligenes. P. pseudoalcaligenes forced to breakdown more hydrocarbons to sustain its metabolic requirement. The bacterial consortium degraded 78.7% of (C12–C34) total aliphatic hydrocarbons (TAHs) and 74.1% of the 16 USEPA prioritized polycyclic aromatic hydrocarbons.