10th U6+ Consortium of African Universities International Conference

This study investigated the efficacy of indigenous microbial biosurfactants produced by 7 bacteria isolated from automobile workshop soils in Ilorin, Nigeria, for the bioremediation of petroleum-polluted agricultural land. Following molecular identification and screening via emulsification index (E24) and oil displacement assays, crude biosurfactants were extracted from seven isolates and applied at concentrations of 1–5% to sterile soil contaminated separately with gasoline and kerosene. The growth of Vigna unguiculata (cowpea) was monitored over a number of days to assess remediation success. The results indicated that biosurfactant application significantly enhanced plant productivity (p < 0.05) compared to untreated hydrocarbon controls. Integrated analysis of growth parameters showed a strong correlation between nutrient uptake and physical biomass; high nitrogen accumulation (up to 19.2 mg/g) and chlorophyll levels (up to 48.7 SPAD) supported a maximum plant height of 28.0 cm and stem diameter of 4.9 mm in gasoline-treated soils. While kerosene treatments generally exhibited higher rates of growth inhibition, Alcaligenes faecalis-CPO1, Pseudomonas aeruginosa -JFF and Alcaligenes faecalis-CPO6 demonstrated broad-spectrum versatility, effectively bridging the growth gap in both contaminants. Post-harvest soil analysis revealed a slight acidification (averaging 0.38–0.48 units), signaling active microbial metabolism and hydrocarbon degradation without exceeding phytotoxic thresholds. Phytotoxicity assays confirmed a germination index >70\%, indicating low residual toxicity. These findings demonstrate that indigenous biosurfactants, particularly from Alcaligenes faecalis-CPO1, Pseudomonas aeruginosa -JF5, and Alcaligenes faecalis-CPO6, are effective potential agents for restoring hydrocarbon-polluted soils and supporting agricultural productivity essential for Nigerian farmland rehabilitation.