Screening of Hydrocarbon-degrading Bacteria Isolated from Petroleum-contaminated Soil and their Potential for Bioremediation of Lead (Pb) Contaminated Soil

Abstract

Petroleum-contaminated soil poses significant environmental challenges, necessitating effective bioremediation strategies. This study was aimed at the isolation and screening of hydrocarbon- degrading bacteria from four petroleum-contaminated sites, Including Sokoto Old Garage (SOG), Illela Garage (ILLG), Buzaye (BZY), and Trailers Garage (TG) and study their potential to remediate Lead-contaminated soil. Mineral salt media was used for screening of hydrocarbon- degrading bacteria after isolation with Nutrient agar. The physicochemical analysis of the petroleum-contaminated soil was done according to standard methods. The lead bioremediation potential of the bacterial isolate was determined using Atomic absorption spectroscopy (AAS). The physicochemical analysis of the soil revealed pH for Illela garage (ILLG) 6.57±0.466b while Sokoto Old Garage (SOG) had 7.085±0.021a. Electrical conductivity for Trailers Garage (TG) 149.35±1.626c while Illela garage (ILLG) had 938.5±192a. Cation exchange capacity for Trailers garage (TG), was 5.715±0.049d while Sokoto old garage (SOG) had 16.625±0.304a. all were indicating site-specific contamination profiles. Bacterial colony counts for Illela garage (ILLG) was 2.00×106±0.028c CFU/g) while Sokoto Old Garage (SOG) had 51.59×106±0.113a CFU/g. In this study eight (8) Bacterial species were identified, namely Pseudomonas putida, Bacillus alvei, Proteus vulgaris, Klebsiella pneumonia, Staphylococcus aureus, Actinomyces viscosus, Bacillus licheniformis, Bacillus subtilis. Pseudomonas putida that exhibited the highest potential in hydrocarbon degradation was identified using molecular techniques. Spectrophotometric analysis at 600 nm showed that Pseudomonas putida and Bacillus subtilis demonstrated the highest hydrocarbon degradation rates over a three-day period, with Pseudomonas putida achieved 2.194±0.257 absorbance and Bacillus subtilis achieved 1.887±0.090. Lead bioremediation potential was assessed using Atomic Absorption Spectrophotometry. Pseudomonas putida reduced lead concentrations from 300 mg/L to 185±1.41mg/L over 72 hours, while Bacillus subtilis achieved a reduction to 227.5±0.70 mg/L. This study demonstrated that Pseudomonas putida isolated from petroleum-contaminated soil had the highest potential for lead bioremediation which can be used to remediate lead contaminated sites.