Potential of Fungi Isolated from Diesel Contaminated Soil to Degrade Diesel

Diesel is a complex mixture and a common pollutant, consisting mainly of aliphatic hydrocarbons ranging from C9 to C23 and a number of aromatic compounds. The main purpose of this study was to isolate fungi from diesel contaminated soil for biodegradation of diesel contaminated soil. Two fungal species (Aspergillus flavus and Saccharomyces cerevisiae) were isolated from a diesel contaminated site using cultural and biochemical characterisation. The isolates were screened for their ability to utilize diesel as carbon source. The biodegradation rate of the fungi isolated was measured by determining the optical density using spectrophotometry. The fungal isolates were further tested for utilisation of hydrocarbons using mineral salt medium (MSM) supplemented with diesel in varying concentrations (1%, 2%, 5% and 10%). The optimum pH for biodegradation (4, 6 and 8) was determined. Both isolates degraded best at 5% diesel concentration with optical densities of 1.751 and 1.546 for A. flavus and S. cerevisiae, respectively. The optimum pH for A. flavus was pH 8 (optical density 1.390), while the optimum pH for S. cerevisiae was pH 6 (optical density 1.234). The results of this study showed that the isolates were able to degrade 5% diesel concentration at optimum pH of 8, and can be developed to remediate diesel contaminated environment. Keywords: Diesel; biodegradation; Aspergillus flavus; Saccharomyces cerevisia