Surface Activity of Extracellular Products of Bacteria Isolated from Petroleum Contaminated Soil

Abstract

Soil samples contaminated with petroleum products were obtained from automobile workshops in Nsukka and Coal Camp in Enugu. The waste lubricating oil (carbon source 1), WLO, was similarly obtained alongside the soil. The Waste frying oil was obtained from fried food vendours, all at Enugu State Nigeria. 10 g of the soil sample was measured into 250 ml Erlenmeyer flask containing 40 ml of basal fermentation medium in the different carbon sources. The pH of the medium was adjusted to 7.0 after addition of the carbon sources. A ten-fold serial dilution of the incubated samples was carried out. Basal medium containing the different carbon sources and solidified with agar was plated by titrating 0.1ml of the appropriate dilution of each sample on the plates. The plates were incubated at 30⁰± 2⁰C for 48 h, two representative colonies were picked from different plates based on their colonial characteristics. These isolates were streaked on nutrient agar plates for purification and the isolates characterized presumptively. The purified isolates were transferred to slants and stored for biochemical tests, all the isolated strains were tested for haemolytic activity which is an indication of biosurfactant production and used as a rapid method for bacterial screening. The surface activity parameters investigated were surface tension and emulsification index. The bacterial screening showed only Bacillus and Pseudomonas as having clear zones of haemolysis on solid blood agar medium which was a positive test for biosurfactant production. The obtained bacteria isolates were now used for the surface activity investigation which showed varying degree of surface activities in the different carbon sources used. The result shows that the isolates (Bacillus and Pseudomonas sp) obtained from the soil samples produced biosurfactants using different carbon sources (WLO and WFO), the stability studies shows that the surface activity of the produced biodurfactants were stable over wide range of environmental condition tested, hence their suitability for environmental, pharmaceutical, cosmetics and agricultural application.