Biosurfactant Production in Soil Amended With Diesel Using Fungi Isolated from a Mechanic Workshop Soil in Dan-Magaji Zaria, Kaduna State

The increasing contamination of soils by petroleum hydrocarbons has intensified the search for environmentally sustainable remediation technologies. Biosurfactants, which are surface-active compounds produced by microorganisms, have gained significant attention due to their biodegradability, low toxicity, and effectiveness under extreme environmental conditions. This study investigated fungal biosurfactant production from hydrocarbon-contaminated soils collected from mechanic workshops in Danmagaji, Zaria, Kaduna State, Nigeria. Physicochemical analysis of the soil revealed slightly acidic conditions, moderate electrical conductivity, and low moisture content, and elevated temperatures typical of hydrocarbon-polluted environments. Fungal isolation yielded four species: Aspergillus flavus, Aspergillus niger, Penicillium notatum, and Fusarium oxysporum. Screening for biosurfactant production using oil spreading, drop collapse, and emulsification index (E24) assays identified Aspergillus flavus and Fusarium oxysporum as positive producers. Biosurfactant production in Mineral Salt Medium (MSM) amended with diesel demonstrated higher yields in A. flavus (0.00152 g/mL) compared to F. oxysporum (0.00136 g/mL). The findings confirm the potential of indigenous fungal isolates to utilize diesel as a carbon source for biosurfactant synthesis and highlight their applicability in the bioremediation of hydrocarbon-contaminated soils.