iarjalsIARJALSIARJALS2708-5104https://doi.org/10.47310/iarjals.2021.v02i02.005Biosurfactant Activity of Candida tropicalis and Aspergillus clavatus Isolated from Oil-Polluted SoilMbachuA.E.MbachuN.AChukwuraE.IDepartment of Applied Microbiology & Brewing, Faculty of Biosciences, Nnamdi Azikiwe University, Awka, NigeriaDepartment of Human Biochemistry, Faculty of Basic Medical Sciences, Nnamdi Azikiwe University, Nnewi Campus, NigeriaBiosurfactants are surface-active molecules synthesized by microorganisms which have both hydrophobic and hydrophilic domains and are capable of lowering the surface tension and the interfacial tension of the growth medium. They are more active and less toxic than the chemical surfactants which are more difficult to degrade from the environment. The aim of this study was to determine the biosurfactant activity of fungi: Candida tropicalis and Aspergillus clavatus isolated from oil polluted soil. C. tropicalis and A. clavatus were isolated from soil samples obtained from three automobile workshops at Old Motor Spare Parts, Nkpor, Nigeria, using the spread plate technique. They were identified using the standard methods and confirmed using 18S rRNA gene sequence. Biosurfactant activities of the isolates were determined using the emulsification index (E24), oil spreading technique and microbial cell surface hydrophobicity in three different oils: used engine oil (UEO), diesel and petrol. Data were analyzed using analysis of variance (ANOVA) at p = 0.05. The biosurfactant activity of the isolates showed high emulsification index (>50%), oil displacement area (ODA) (>4.5 cm2) and cell surface hydrophobicity (>50%) in UEO, diesel and petrol. However, the E24 of the isolates were significantly higher in petrol (p< 0.05) compared with UEO and diesel. The broth culture containing A. clavatus showed significantly higher ODA in petrol (p< 0.05) when compared with UEO and diesel. The isolates C. tropicalis and A. clavatus showed biosurfactant activity in UEO, diesel and petrol, thus have promising potential against different hydrocarbon pollution.