Laboratory Study of Microbial Cleaning of Oil Spills Under Saudi Environmental Conditions

Abstract

ABSTRACT An active strain of Pseudomonas sp. isolated from oil-contaminated soil at the Arabian Gulf was able to utilize the crude oil at a concentration of 5 mg/ml added to sterile Gulf water. Microbial growth and gas chromatographic analysis of the remaining oil were used as a criteria for oil degradation by this strain. The bacteria at a cell density of 105 CFU/ml was able to degrade the crude oil at concentrations ranged from 2.5 to 15 mg/ml in Gulf water samples. At low concentration (2.5 mg/ml), about 70% of crude oil had disappeared within 7 days. At high concentration (15 mg/ml), the extent of oil degradation decreased, where only 50% of the added oil had disappeared. The rate of degradation by the inoculated bacteria was slightly increased by the addition of inorganic nutrients, mainly P or N to the Gulf water. The degradativ capacity of Pseudomonas sp. was optimum when the bacteria was incubated at 25°C, where 47% of the added oil has disappeared within 5 days of incubation. Low cell density (103 CFU/ml) of the degrading bacteria required a long lag period before initiation of oil degradation, whereas high cell density (106 CFU/ml) rapidly degraded oil with a short lag period under the same conditions. This strain could be useful in decontamination of spilled oil in Gulf water if it acts well under field trial test and survived for a reasonable period sufficient for oil biodegradation.