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(-1) Tapis 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 x 10(-10) mg kg(-1) cell(-1) day(-1) Tapis 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 x 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 (C-12-C-34) total aliphatic hydrocarbons (TAHs) and 74.1% of the 16 USEPA prioritized polycyclic aromatic hydrocarbons. (C) 2008 Elsevier Ltd. All rights reserved.