SOURCE:

Faculty: Biosences
Department: Applied Microbiology And Brewing

CONTRIBUTORS:

Chizoba, M.D;
Chukwura, E.I;

ABSTRACT:

Crude oil has remained one of the major pollutants in Nigeria. The use of biosurfactant producing bacteria Isolatesto remove this pollutant was assessed. The physicochemical properties and microbiological analysis of the polluted soil collected from Ibeno polluted site and unpolluted soils collected from Ibeno and Otuocha agricultural soils were carried out. Bacteria were isolated from the polluted soil while the unpolluted agricultural soils were artificially polluted with crude oil. The isolated organisms were characterized while bacterial metagenomics analysis and fungi characterization was done on the artificially polluted soil. The isolated bacterial were screened for their ability to degrade crude oil and produce biosurfactant. Parameters like pH and optical density were used in determining the growth profile. Residual crude oil was analysed using gravimetric and gas chromatography method. Bioremediation exercise was then done on the artificially polluted agricultural soil. pH and total viable count was used in determining the progress of remediation in the soil. The success of the remediation was determined using gas chromatography profile, the soils physicochemical properties were also carried out. Bean seed was also planted to determine the ability of the remediated soil to support seed germination.The physicochemical properties of the polluted soil used for microbial isolation was 71.5 for electrical conductivity, 0.1987ppt for salinity, 24.4803cmol/kg for cation exchange capacity, 2.016% for nitrogen content, 2.55% for total organic carbon and 5.98% for phosphorus. The soil contained more of sand than clay and silt and other heavy metals were also determined.The physicochemical properties of the soil before crude oil pollution showed that Ibeno soil contained more sand and silt while Otuocha contained more clay. Some other physicochemical properties of Ibeno and Otuocha soil samples were pH 5.9 and 6.1, mercury 0.450 and 0.00, arsenic 0.184 and 0.083, nitrogen 0.336 and 0.672, carbon 0.0510 and 0.1275, phosphorus 7.82 and 8.79 respectively. The physicochemical properties of the soil after crude oil pollution for Ibeno and Otuocha soil samples were pH 6.19 and 5.97, mercury 1.039 and 0.216, arsenic 2.281 and 1.518, nitrogen 0.112 and 0.336, carbon 1.0772 and 0.3294, phosphorus 32.59 and 38.52 respectively.The microbial enumeration showed a decreased after crude oilpollution. The isolated organisms were identified asTsukamurellainochensis and Gordoniaalkanivorans. The metagenomic analysis of the bacteria in the soil showed that some of the genera present in the soil after pollution were Massilia, Phenylobacterium, Gordonia, Roseomonas, Microbacterium, Bacillus, Pseudomonas, Planococcus, Parviterribacter, Cellulomonas, Mycobacterium, Nocardioides, Tumebacillusetc. The fungi isolates characterized were AspergillusLentulus and Cylindrocarpon.The mean percentage degradation of 100ul, 500ul 1000ul and 2000ul concentrations of crude oil by the isolate using gravimetric methods were 33.33%, 26.92%, 21.28% and 15.73% for Gordoniaalkanivorans and 50.00%, 42.31%, 25.53% and 17.98% for Tsukamurellainochensis. The pH of 28 days’ degradation tends towards acidity for the medium containing the test isolates but no detectable change was noticed for that of control. The optical density increased gradually but started decreasing from the 21st day.The polycyclic aromatic hydrocarbon (PAH) content after 28 days of biodegradation were5510.4443 for the control, 869.8653 forGordonia, 476.5867 for Tsukamurella and252.4649 for mixed culture while the total petroleum hydrocarbon (TPH) content were 10541.4180 for control, 1463.7610 for Gordonia, 619.0704 for Tsukamurellaand269.8244 for mixed culture. The mean pH value of remediation exercise was between 5.61-6.87 before tending towards alkaline at the end of the remediation exercise. The total viable count increased gradually from the 4th week before decreasing on the 20th week. The PAH of Ibeno soil before remediation was 1191.1993 but treatment with Gordonia reduced it to 8.53390, 3.22127 byTsukamurella, 1.04768 bytheir mixed cultureand the control was 11.00143. Otuocha soil PAH before remediation was 1879.1443but treatment with Gordonia reduced it to 516.9339, 539.6178 by Tsukamurella,340.6747 by their mixed culture and control value was 550.2319. TPH ofIbeno soil before remediation was 1975.2632 but treatment with Gordoniareduced it to 563.41279, 510.29552 byTsukamurella,585.09108by their mixed culture while control value was 778.76791. Otuocha soil before remediation was 3244.9021 but treatment with Gordonia reduced it to 559.55518, 526.17757 byTsukamurella, 985.96555by their mixed culture while control value was 1326.70729. A significant difference (p<0.05) was observed for both TPH and PAH of the tested isolates and their control.The physicochemical parametresanalysedafter remediation showed that no crude oil was detected in the soil containing the tested isolates but was detected in the control; the water permeability of the control was negative while positive in the test samples. The nitrogen content, total organic carbon and phosphorus all decreased after remediation. The bean seed planted after remediation showed that the test samples and their positive control have a better plant growth than thenegative control. This research work showed that biosurfactantproducing bacterial isolates like Tsukamurellainochensis and Gordoniaalkanivorans can actually be used in cleaning up crude oil pollution from the environment.