Biodegradation of Crude-oil by Fungi Isolated from Cow Dungcontaminated soils

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).