Bioremediation potentials of bacteria isolates from hydrocarbon contaminated soil of Nakasari area of Sokoto Metropolis, Sokoto state, Nigeria

Abstract

Hydrocarbon contamination of soil remains a significant environmental problem in many urban and semi-urban areas due to indiscriminate disposal of petroleum products and continuous mechanical activities. This study investigated the emulsification activity and hydrocarbon utilization potential of bacteria isolated from hydrocarbon-contaminated soil collected from Nakasari, Sokoto metropolis, Sokoto State, Nigeria. Soil samples were collected from mechanic workshop sites and subjected to standard microbiological analyses for isolation, enumeration, and characterization of bacterial species. A total of five bacterial species were identified using morphological and biochemical tests, namely Bacillus subtilis, Bacillus megaterium, Bacillus thuringiensis, Paenibacillus polymyxa, and Bacillus cereus. The emulsification activity (E24) of the isolates was evaluated using used engine oil as the hydrophobic substrate, while hydrocarbon utilization potential was assessed by monitoring changes in optical density (OD600) in mineral salt medium supplemented with petrol as the sole carbon source over a 12-day incubation period. The results showed varying emulsification indices among the isolates, with Bacillus cereus exhibiting the highest emulsification activity (50.0%), while Paenibacillus polymyxa showed the lowest (36.7%). All isolates demonstrated the ability to utilize hydrocarbons, as indicated by progressive increases in optical density, with Bacillus cereus and Bacillus subtilis recording the highest growth rates. The findings indicate that hydrocarbon-contaminated soils in Nakasari harbour diverse bacterial species with significant emulsification and hydrocarbon degradation capabilities. These indigenous bacteria possess strong potential for application in the bioremediation of hydrocarbon-polluted environments.