Rate of biodegradation of crude oil by microorganisms isolated from oil sludge environment

The rate of biodegradation of crude oil by micro-organisms isolated from crude oil sludge environment in Eket, Akwa Ibom State of Nigeria was studied. Mineral salt medium supplemented with crude oil was used and three most abundant species isolated from a crude oil sludged soil - Micrococcus varians, Bacillus subtilis and Pseudomonas aeruginosa were selected for the degradation test. The microbial counts used as index during the degradation process for each of the organisms ranged from 1.8 to 6.4 x105 cfu/g for P. aeruginosa, 1.5 to 5.2 x 105 cfu/g for M. varians and 1.3 to 4.7 x 105 cfu/g for B. subtilis. P. aeruginosa degraded 97.2% of the oil introduced into the medium followed by M. varians with 85.7% degradation. The least was B. substilis with 72.3% degradation of the oil. P. aeruginosa was found to have the highest rate of degradation.