Assay of Oil-Degrading Potential of Fungi Isolates on Diesel, Kerosene and Petrol Using Enrichment Method.

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A study was carried out to assay for oil-degrading potential of fungi isolates on diesel, kerosene and petrol. Water samples were collected aseptically and analyzed microbiologically using standard techniques. The fungi isolated from the water samples were: Trichoderma viridae, Aspergillus niger, Aspergillus fumigatus and Stochyborys atra. The confirmatory test for oil utilization potential of the isolated fungi was carried out using the enrichment method, minimal salt broth (MSB). There were variations in the growth patterns of each of the fungal species with respect to the different oil (diesel, kerosene, petrol) used. This also signified that fungal species varied in their degradative abilities. The length of incubation for the fungi ranged from the 5th day to the 20th day. The fungi with the highest hydrocarbon utilization potentials were: Aspergillus fumigatus and Aspergillus niger while stachyborys atra had the least hydrocarbon utilization potential. These hydrocarbon degraders are capable of utilizing oil polluted river and could therefore be employed in bioremediation process. *Corresponding Author:

Institute of Microbial Biotechnology and Metagenomics, University of the Western Cape, South Africa

KEYWORDS: oil–degrading potential, microorganism, polluted land, hydrocarbon degraders, enrichment medium

The huge demand for crude oil causes enormous quantities to be moved from production areas to different destinations where the oil will be used. The greatest environmental problem connected with crude oil exploration in Nigeria is oil spill both on-shore and off-shore (Okpokwasili, 1996). Crude oil, because of its characteristics, is one of the most significant pollutants in the environment as it is capable of causing serious damages to humans and the ecosystem, resulting in the contamination of drinking water, killing the fishes and poisoning aquatic life, thereby, placing hardship on those who make their living by fishing. Regardless of the source of contamination, some oil or decomposition products may reach groundwater reserves, lakes and other water bodies, polluting water for domestic and industrial use, thus posing serious threat to public health and causing socio-economic hazards to the populace using the water (Okpokwasili, 2003). When oil enters the ocean, it quickly begins to spread and disperse with the aid of the winds and waves while some will evaporate due to its high volatility, some will form into tar balls and sink to the bottom where they may remain for a long time, slowly releasing hydrocarbons into the water. Though oil is toxic, it becomes less so with time. Winds and waves help spread and disperse the oil. Some oil will evaporate. Microorganisms in the water attack and digest the oil. If people act quickly after the spill, they can scoop up some of the oil and stop it from causing worse damage to the environment (Swannell and Richard, 2003). Many microorganisms are found to posses the ability to actively decompose specified fractions of hydrocarbon (Bartha and Atlas, 1997). Since not all components of petroleum–derived hydrocarbon mixture are decomposed simultaneously, Yuan et al. (2000) suggested the introduction of mixed culture of bacteria and fungi for the degradation of petroleum. However, single cultures of fungi have been found to be better than mixed cultures (Okerentugba and Ezeronye, 2003). The filamentous fungi are known to possess some attributes that enable them as good potential agents of degradation, such as digestion of the hydrocarbons through the secretion of extracellular enzymes and ability to grow under environmental conditions of stress (low pH values, low nutrients and low water activity) (Ojo, 2006). Different techniques have been employed to clean up...
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