Hydrocarbon Degradation Potentials of Fungi Associated with Oil-Contaminated Soil from Selected Mechanic Workshops in Awka, Anambra State, Nigeria

Abstract

Biodegradation potentials of soil mycobiota isolated from five automobile mechanic workshops and a farmland in Awka town on engine oil were investigated using standard methods. The place has variable climatic condition with peak of annual rainfall in August and temperature range of 32 - 42°C. Heterotrophic fungal counts from the soil samples in colony forming unit per gram (cfu/g) ranged from 2.0 x 103 to 3.0 x 103. Hydrocarbon utilizing fungal counts ranged from 0.7 x 103cfu/g to 1.2 x 103cfu/g. The statistical analysis of the mean values using analysis of variance showed that, there was no significant difference at P < 0.05. Fungal isolates identified as engine oil degraders using cultural, morphological and biochemical characteristics include; Aspergillus niger, Aspergillus fumigatus, Penicillium xingjiangense, Mucor racemosus, and Rhodotorula sp. Biodegradation ability of the selected fungi on engine oil was studied in a shake- flask culture and the residual hydrocarbon content was measured. The culture fluid for the biodegradation assay was Bacto Bushnell-Haas broth with 10% (V/v) engine oil and 0.1% (V/v) Tween 80. Incubation was at 25°C for 28 days on an incubator-shaker. The results showed decrease in the pH values and hydrocarbon content. Mixed culture had higher percentage hydrocarbon reduction (83.4%) than the axenic cultures: Aspergillus niger (79.3%); Penicillium xingjiangense (73.7%); Aspergillus fumigatus (71.7%) and Mucor racemosus (69.1%). They were subjected to gas chromatography on specific polycyclic aromatic hydrocarbons biodegradation. It was observed that Aspergillus niger and Penicillium xingjiangense were more effective in PAHs reduction when compared with the control sample. Hence, further studies need to be done to confirm that Aspergillus niger and Penicillium xingjiangense can be used for bioremediation of engine oil contaminated soil.