Abstract

Soil and water contamination with crude oil is a major global problem that can be addressed by using phytoremediation. The technology makes use of the synergy between the plant and its microbial population to achieve complete mineralization of contaminants. This research focuses on the role the fungal rhizosphere community can play in this relatively new technology. The aim of this study is to investigate the possibility of Aspergillus niger isolated from the rhizosphere of Helianthus annuus a known phytoremediant to convert petroleum hydrocarbons to its own mycelia biomass. A. niger isolated from the rhizosphere of H. annuus was cultured in crude oil contaminated minimal salt broth and control broth without crude oil and biomass production monitored for a period of 30 days. Two methods were used for biomass estimation; the dry weight method and also the spectrophotometric method at 540nm. The concentration of residual petroleum hydrocarbons in the treated and control broths were got using GC-FID. The growth indices got indicate that the fungus A. niger used crude oil as its sole carbon source converting it to its own biomass. There was gradual increase in biomass production until the 30^th day, where senescence set in. There was a concomitant reduction in the concentration of total petroleum hydrocarbons from 3867mg/l in the control to 504.99mg/l in the A. niger treated medium. There was no significant difference between the dry weight and spectrophotometric methods. The spectrophotometric method is preferred to the dry weight as it is faster and easier to complete. Aspergillus niger in the root zone of Helianthus annuus has the potential to degrade up to 70% of petroleum hydrocarbons and can therefore be used for bio-augmentation during phytoremediation of crude oil polluted sites with the plant Helianthus annuus.