Enhanced Biodegradation of Heavy Hydrocarbons by Aspergillus Pseudodeflectus F13 in the Presence of Rhamnolipid

The aim of this study was to investigate the ability of mold isolates in degradation of petroleum pollutants and also the effect of surface active compounds in enhancing the removal efficiency. In this study, 40 mold isolates were isolated from an aged petroleum contaminated area, and the capability of petroleum biodegradation of these isolates was studied. Identification of selected isolate based on ITS gene sequencing revealed that the F13 isolate had 100% similarity to Aspergillus pseudodeflectus. The results of the crude oil degradation showed that this isolate was able to remove 52.97% crude oil within 21 days. The extents of biodegradation for pyrene as a heavy PAH (at 500 ppm) and tetracosane as a long-chain aliphatic compound (at 10000 ppm) were measured to be 49.06% and 55.73% respectively. These results indicated the recalcitrance of pyrene towards biodegradation in comparison with tetracosane. To investigate the effect of surfactants on the degradation of these compounds, rhamnolipid (0.01% w/w) as a biosurfactant and Tween 80 as a chemical surfactant (0.2% w/w) were used. Rhamnolipid showed a better effect in comparison with Tween 80 and increased the efficiency of crude oil, pyrene and tetracosane biodegradation for about 25, 16 and 30% respectively. These results showed that rhamnolipid had a higher positive effect than tween-80, even in a lower concentration. Also, the surfactants have a more enhancing effect on degradation of aliphatics compared to aromatics. Finally, the results of this study can be promising for the use of fungal isolates in the bioremediation of aged and recalcitrant petroleum pollution.