Gravimetric Profile of Hydrocarbon Degrading Bacterial and Fungal Isolates from Contaminated Soil Samples in Ado-Ekiti, Nigeria

Abstract

One of the biological compounds limiting soil water retention capacity is oil when present due to its hydro-nature. However, somemicroorganisms exhibit the capacity to degrade oil as a source of carbon, whereby the soil quality is retained and enhanced. Hence,the gravimetric profile of hydrocarbon degrading bacteria and fungi isolated from oil contaminated soil samples was investigated.Soil samples were collected from surface and 10m depth from six different mechanic workshops and generator sites. The pourplate technique was used to isolate the microorganisms. All pure isolates were sub-cultured using Bushnell Haas agar and theisolated bacteria were identified by their morphological and biochemical characteristics. The soil samples pH range was 4.3 -6.4. Bacteria isolated included Pseudomonas spp., Staphylococcus spp., Microccocus spp., Acinetobacter spp., and Bacillus spp.The fungi isolated included Aspergillus spp., Rhizopus spp., Candida spp., Trichoderma spp. and Penicillium spp. Degradation ofkerosene, diesel, crude oil, engine oil, and spent engine oil was allowed using Acinetobacter baumanni, P. aeruginosa, B. subtilis,and S. aureus. Gravimetric analyses were used to determine the percentage of petroleum hydrocarbon degraded by bacterialisolates. The highest percentage of degradation was between P. aeruginosa and B. subtilis. Pseudomonas aeruginosa degraded97.4% diesel, 88.2% kerosene, 71.3% crude oil, 80.7% engine oil and 78.2% spent engine oil; while Bacillus subtilis degraded71% diesel, 97% kerosene, 89.6% crude oil, 87% engine oil and 72.6% spent engine oil. This study revealed that bacterial andfungal isolates from oil contaminated soils exhibited the potentials to degrade oil and bioremediation using these microorganismswas possible.