Abstract
This study assayed oil-degrading potential of fungi isolated from cow dung-contaminated soils. The samples were collected aseptically from four different cow dung dumping sites with no history of crude-oil pollution in Akure metropolis. These samples were analyzed for fungal loads and oil-degrading fungi using potato dextrose agar and mineral salt medium respectively. The biodegradation of crude oil was observed spectrophotometrically using the broth culture of the fungal isolates for a period of 15 days on mineral salt medium. The fungi were identified based on the microscopic and macroscopic features of the hyphal mass, nature of the fruiting bodies and the morphology of cells and spores. The sixteen (16) fungi identified from the contaminated soils include; Bdellospora helicoides, Aspergillus fumigatus, Gonadobotricum apiculata, Aspergillus niger, Trichoderma viridae, Pleurothecium recurvatum, Streptothrix atra, Thysarophora longispora, Candida albicans, Aspergillus flavus, Helminthosporium velutinum, Botrytis cinerea, Zoophage nitospora, Varicosporium elodeae, Articulospora inflata and Neurospora crassa . All fungi showed degradation of the crude oil, with Trichoderma viridae, Aspergillus flavus and Varicosporium elodeae demonstrating best degradation ability. Trichoderma viridae exhibited highest degradation (66.2%) while Varicosporium elodeae exhibited least degradation (40%). The measurement of the rate of biodegradation of crude oil by the three fungi was further confirmed using Gas Chromatography and Mass Spectrophotometer (GC-MS). The GC-MS analysis showed that the fungi degraded the hydrocarbon compounds when compared to that of the control. The result obtained revealed that oil-degrading fungi can be isolated from cow dung dumping sites and they are competent mycoflora for the biodegradation of crude oil polluted soils. They can be used as a better approach to restoring oil contaminated environments through bioremediation process. Keywords : Biodegradation, Mycoflora, Crude-oil, Gas chromatography and Mass spectrophotometer (GCMS).
Highlights
The common problems associated with petroleum industry are accidental and deliberate discharge of oil spills
Trichoderma viridae, Aspergillus flavus and Varicosporium elodeae had the best growth in the mineral salt broth after 15 days of incubation
It was observed that after 4, 8 and 12 days of incubation the organisms did not show any significant degradation but after the 16th day of incubation, it was observed that Trichoderma viridae degraded the crude oil best while Varicosporium eloedea was the least in degrading it
Summary
The common problems associated with petroleum industry are accidental and deliberate discharge of oil spills. Many approaches (physical, chemical and biological methods) have been employed in order to reduce or eliminate the effect of oil spillage on the environment and living organisms. Most of these efforts have limitations in their applications, either as being too expensive or posing threats to the ecosystem. The most promising of many researches carried out to deal with large-scale oil spills is the use of microorganisms to provide an effective alternative (Singh et al, 2001) This approach is referred to as ‘bioremediation’, and it is one of the most rapidly growing areas of environmental microbiology, which has been used for cleaning up pollutants. Microbial degradation represents the major route responsible for the ecological recovery of oil spills (Johnsen, et al, 2005)
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