Abstract
The ability of different local fungal isolates to degrade diesel fuel in liquid medium was studied. The results showed that the percent of diesel degradation varied among the different tested fungi and that 92-100% of diesel was degraded after 7 days in presence of 0.2% (v/v) of tween 80. The degradation process by A. ustus and A. alternata was significantly influenced by the incubation period, and 7 days of incubation was sufficient for complete diesel degradation. As the diesel fuel concentration increased up to 6% (v/v), more than 75% was degraded by the two strains. The degradation process was enhanced using fungal consortium of A. alternata and A. ustus at different inoculum sizes and elevated surfactant (tween 80) levels. Statistical experimental designs were used to optimize the process of diesel degradation by the fungal consortium. Under optimized medium compositions and culture conditions, overwhelming degradation increase (100%) for 4 mL of diesel/25 mL medium (16%, v/v) was recorded. Optimal conditions obtained in this work provided a solid foundation for further use of the fungal consortium (A. alternata and A. ustus) in treatment of diesel polluted soil. The consortium under the optimized conditions efficiently degraded diesel polluted soil, 12.5% (v/w), after 35 days of incubation.