| Crude oil contributes a major percentage to the source of energy used on earth,however,hydrocarbon components have been classified to the family of carcinogens and neurotoxic organic pollutants.The inappropriate drilling,transportation,and usage lead to the increment of soil,air,and water body petroleum hydrocarbon pollution.If this menace is not put in check as a matter of urgency,it can cause an epidemic outbreak in an affected community,shortage in agriculture produces output,threatening of soil useful microbial biome and environmental disaster.Bioremediation as promising modern biotechnology is capable of mineralizing hydrocarbon pollutants into water,carbon dioxide,cell proteins,and an inorganic compound.Indigenous or genetically modified microbes are able to secrete enzymes for the synthesis ofBiosurfactants that break down organic pollutants into a less toxic form.Bioremediation is not only potent in degrading organic pollutants,but it is also environmentally friendly and cheap compared to other non-natural methods.Therefore,this study investigates some highefficiency hydrocarbon-degrading bacteria strains for effective biodegradation of petroleum hydrocarbon polluted environment.Five hydrocarbon degrading bacteria strains(B2,B3,B4,and B5 B9)were identified and adopted from the 10 strains isolated from oil sludge and crude oil-polluted soil.These strains were subjected to the DCPIP decoloration test,emulsification index test,and the growth rate of the strains was also measured in the presence of used engine oil as a carbon source.16 S r RNA gene sequencing identified the strains to be Bacillus aerius B2,Psuedomonas stutzeri B3,Ochrobactrum intermedium B4,Micrococcus lylae B5,and Acinetobacter calcoaceticus B9,respectively.The biodegradation test was conducted in a liquid microcosm for individual strain and mixed strains in a controlled environment for 14 days.Oil removal rates were measured after gravimetric and gas chromatography-mass spectrometry analysis.The mixed Consortium comprising the five selected strains could improve the rate of degradation of car used oil by 88%.This result shows that the adoption of appropriate application measures and procedures,controlled inoculation of the above screened and selected hydrocarbons degrading bacterial strains,can enhance the degradation of straight-chain alkanes,branched alkanes,and aromatic hydrocarbons polluted environment than individual strains.In addition,car used engine oil polluted soil degradation experiment was carried out for30 days to evaluate the potential effect of the Biostimulation,bioaugmentation and the combination of both.The effect of cow dungs on growth kinetics of hydrocarbonoclastic bacteria in the polluted soil was also examined.In this study,cow dung was selected as organic waste biostimulator,and five hydrocarbon degrading bacteria strains previously screened and identified from crude oil polluted soil and sludge were adopted as microbial load augments.The result showed that the designed microcosms comprises of organic waste(cow dung),mixed bacterial consortium,and the combination of both were significantly effective in biodegradation.However,the combination of organic waste(cow dung)and effective strains attained a highest percentage of used oil degradation with 92%.Treatment with cow dung,showed 70% of biodegradation,followed by(bacterial strains)augmentation treatment with degradation rate of49% as compared to autoclave control set-up with a degradation rate of 11%.It was also find out that cow dung improved soil physiochemical properties and favors the proliferation of the recolonizing microbes from the environment.The result shows that crude oil polluted soil bioremediation treatment can be improved when the soil is supplemented with cow dung and inoculated with robust bacteria microcosm with high crude oil degradation efficiency.Lastly,winter wheat(Tritium avestivum)pot growth experiment was carried out for 6weeks on the treated 5% concentration level of used engine oil polluted degraded soil,to evaluate the effect of biodegradation level on wheat growth in general.The pot(Cw)with the combination of cow dung and bacterial strains was found to be the best among the degraded polluted soil samples,the wheat attained the height growth of 26.4cm in 6 weeks.Having 7.4%lower in height compared to an unpolluted soil treatment(CTwn)with recorded height of(28.6Cm)and 47.1% higher than the control treatment(CTw)with same level of engine oil pollution in the soil.24.8Cm and 23.1Cm height were record by cow dung amended soil pot(STw)and bacterial strains augmented soil(Aw)respectively.It could also be seen that car used engine oil have effect on the leaves number,reduced leaf length and leaf width.The average records of shoot fresh and dry weight obtained at the(CTw)treatments was significantly lower than that of ASw,STw and Aw treatments.The control treatments without oil pollution(CTwn)had the highest values of 23 g and 1.4g for shoot fresh and dry weight,1.4g and 0.5g for root fresh and dry weight respectively.During degradation,bacteria explored catalytic enzymes to mineralize the car used engine oil,the reaction was possible through secretion of biosurfactants used for emulsification of the oil,thereafter absorbed the emulsified oil into the cytoplasm through endocytosis,passive or active transport system.In the cytoplasm,the emulsified oil is absorbed by the mitochondria which later degrade the car used engine oil with corresponding enzymes and released energy in the form of adenosine triphosphates(ATP).In conclusion,the results obtained shown scientific and effective techniques for bioremediation of petroleum oil in aqueous solution and soil environment.The coupling of effective bacterial consortium and cow dung have influences on mineralization of petroleum oil in the soil.Mixed effective bacterial consortium coupling cow dung represent a novel natural and cheap methods for the remediation of oil polluted water and soil environment.Therefore,our results can be suggested for the basic technological treatment of petroleum oil polluted soil,for the cultivation of crops... |
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