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, some microorganisms 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 pour plate technique was used to isolate the microorganisms. All pure isolates were sub-cultured using Bushnell Haas agar and the isolated 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 of kerosene, 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 bacterial isolates. The highest percentage of degradation was between P. aeruginosa and B. subtilis. Pseudomonas aeruginosa degraded 97.4% diesel, 88.2% kerosene, 71.3% crude oil, 80.7% engine oil and 78.2% spent engine oil; while Bacillus subtilis degraded 71% diesel, 97% kerosene, 89.6% crude oil, 87% engine oil and 72.6% spent engine oil. This study revealed that bacterial and fungal isolates from oil contaminated soils exhibited the potentials to degrade oil and bioremediation using these microorganisms was possible.