Evaluation of Indigenous Biosurfactant-producing Bacteria for De-emulsification of Crude Oil Emulsions

Conventional method of removing water from crude oil using chemicals is unfavourable from both the economic and environmental perspectives; so, this study aims at formulating economical and environmentally-friendly biosurfactant de-emulsifiers. Biosurfactant-producing bacteria isolated from oil-contaminated soil samples from Nigerian National Petroleum Corporation (NNPC) depot Apata, Ibadan, Oyo State of Nigeria were applied on crude oil emulsions for the purpose of separating water-in-crude oil emulsions. Thirty-five of 41 bacterial strains were further screened for ability to degrade (de-emulsify) hydrocarbon, using vapour transfer method. Highest displayed de-emulsification activities at 24 h were Pseudomonas sp. AGO1 (50.0%), Bacillus sp. DPK1A (50.0%), Bacillus subtilis AGO1A (50.0%), Pseudomonas aeruginosa DPK3A (55.7%) and Bacillus subtilis PMS1B2 (66.0%); and at 48 h were, Bacillus subtilis AGO1A (50.0%), Ps. aeruginosa DPK3A (60.0%) and Bacillus subtilis PMS1B2 (66.7%). Higher de-emulsification activities were recorded on supplementation of growth media, with Ps. aeruginosa DPK3A showing the highest de-emulsification activity of 66% when grown on growth media supplemented with glucose and yeast extract, at temperature of 60°C. In comparison with chemical de-emulsifier, microbial de-emulsifier produced 66%, 62% and 60% volume of water, while chemical de-emulsifier produced 63%, 60% and 66.2% volume of water. This study demonstrated that generally regarded as safe (GRAS), hydrocarbon-utilising, biosurfactant-producing bacteria, especially the Bacillus species isolated from crude oil-contaminated soils, when cultured on appropriate medium is effective in diesel degradation and treatment of water-in-crude oil emulsion; thus, reducing cost and environmental pollution.