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Soil samples were collected from petroleum exploring area of Mesogar Community in Warri South Local Government Area of Delta State to enumerate and identify hydrocarbon degrading fungi in the soil. Total indigenous fungi on potato dextrose agar were enumerated and those that were able to use crude oil as source of carbon and energy were enumerated using Mineral Salt Media supplemented with 1% and 2% crude oil. Fungal isolates were identified using macroscopic and microscopic examination. The fungi isolated from potato dextrose agar include: Saccharomyces cerevisea, Doratomyces stemonitis, Fusarium poae, Paecilomyces variotii, Penicillium ferquentans, Penicillium chrysogenum, Aspergilus niger, Aspergilus flavus, Rhizoqus stotonifer. Hydrocarbon-degraders isolated from mineral salt broth include: Penicillium chrysogenum, Penicillium ferquentans, Aspergilus niger, Aspergilus flavus, Rhizopus stolonifer. The biodegradative activities of hydrocarbon degrading fungi were determined by calculating the amount of CO2 evolved using titrimetric method. The maximum amount of CO2 evolved was observed with Penicillium chrysogenum, (4180mg/L) on 16th day of treatment and Aspergillus flavus (4180mg/L) on the 12th day with 2% crude oil concentration. Aspergilus flavus declined to 3520mg/L on the 16 th day of treatment with 2% crude oil concentration. Increase in the amount of CO2 evolved was observed with Penicillium frequentans, Aspergilus niger, Aspergilus flavus and Rhizopus stolonifer up to the 12th day of treatment, while decrease was observed on the 16th day of treatment with 2% crude oil concentration. The decrease in the amount of CO2 evolved may be due to accumulation of toxic substances by microbes and exhaustion of nutrients to continue the degradation process with the exception of Penicillium chrysogenum in which the amount of CO2 continues to increase throughout the period of treatment.

Keywords: Hydrocarbon-degrading, fungi, Crude oil, Carbon dioxide, incubation period.