Microbial studies of biosurfactant producing bacteria from crude oil contaminated soil

K.I Ogru,P.G Olannye

doi:10.4314/jasem.v25i9.27

K.I Ogru, P.G Olannye

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https://doi.org/10.4314/jasem.v25i9.27

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Soils contaminated with crude oil collected from three sites in Delta State were analyzed using serial dilution and pour plate methods. The physicochemical characteristics of the soil were determined using standard methods. The mean heterotrophic bacteria count and the mean hydrocarbon utilizing bacteria count were also determined. Blood haemolysis, foaming activity, oil spreading techniques and emulsification assay was used to screen the microorganisms for biosurfactant production. The biosurfactant producing bacteria were selected and their effect on metal removal and growth kinetics was also determined. The pH of the contaminated soil samples ranged 4.82 to 5.62. The mineral elements such as potassium (k+) and sodium (Na+) ranged from 0.20 to 0.80 Meq/100g and 0.07 to 0.81 Meq/100g respectively. The heavy metal content such as zinc (Zn2+) and lead (Pb2+) ranged from 10.13 to 19.24 mg/kg and 19.24 to 49.63 mg/kg respectively. Organic carbon and THC ranged from 5.44 to 6.87 % and 2720.00 to 3110.00 mg/kg respectively. The mean heterotrophic bacteria and hydrocarbon utilizing bacteria ranges from 1.4 ± 0.4 x 106 to 1.6 ± 0.7 x 106 and 1.0 ± 0.2 x 106 to 1.2 ± 0.4 × 106 respectively in the soil samples. Bacteria isolated and identified from the three sites include Corynebacterium spp., Bacillus subtilis., Pseudomonas aeruginosa, Micrococcus varians, Streptococcus spp., Klebsiella spp. and Enterobacter spp. with Bacillus subtilis and Pseudomonas aeruginosa having the highest prevalence and among these isolates only Corynebacterium spp., Bacillus subtilis., Pseudomonas aeruginosa and Micrococcus varians showed positive result for the production of biosurfactant. Bacillus subtilis had the highest metal removal capacity of 29.44% of 100 ppm of lead. Corynebacterium spp. and Bacillus subtilis had an optimum growth at pH 8 and 7 respectively while Pseudomonas aeruginosa and Micrococcus varians has an optimum growth at pH.

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Biosurfactant are surface active molecule that are mainly synthesized extracullarly and as part of cell membrane by certain microorganisms which are amphyphilic in nature, that is, having hydrophilic and hydrophobic moleties which confers them with the capacity to exist between phases such as water/air or water/oil, helps to minimize the surface and interfacial tension of the surface and interface respectively (Banat 1995; Karanth et al, 1999)
Microbial degradation of soil polluted with crude oil is the major natural means of remediating crude oil contaminated environment (Akpoveta et al, 2011) and more biosurfactant producing microorganisms should be identified, studied and employed in remediation process as diverse groups of bacteria and fungi have been isolated from soils polluted with crude oil and shown to produce biosurfactant and degrade hydrocarbon in the laboratory
The physicochemical result given in (Table 1) shows that the soil samples are acidic with pH ranging from 4.82 to 5.62

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Biosurfactant are surface active molecule that are mainly synthesized extracullarly and as part of cell membrane by certain microorganisms which are amphyphilic in nature, that is, having hydrophilic (water loving) and hydrophobic (exclude water) moleties which confers them with the capacity to exist between phases such as water/air or water/oil, helps to minimize the surface and interfacial tension of the surface and interface respectively (Banat 1995; Karanth et al, 1999). Enumeration and Isolation of Hydrocarbon Utilizing Bacteria:Bacteria with hydrocarbon degrading ability were isolated from the contaminated soil samples using mineral salt agar that is added with15 g of agar and about 1 % crude oil as carbon source (Amund et al, 1987), with a final pH of 7.0. The Effect of Biosurfactant Producing Microorganism on Metal Removal: The isolates was grown in nutrient broth at a neutral pH in the presence of 100 ppm of lead and are incubated for 5 five days (37oC, 120 rpm) to allow the interaction of the organisms with the metal ions.

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