Assessment of diesel degrading potential of fungal and bacterial isolates from Egypt

Abstract

Two naturally occurring fungal and bacterial species, Aspergillus flavus and Bacillus sp. H6 strains, were capable of utilizing diesel oil as a sole source of carbon in synthetic microcosoms. The initial diesel oil contamination of 1666 mg kg dry soil was reduced to 166.667 mg kg after 150 days of incubation in fungal-bacterial consortium microcosm. That is mean 89.9%, of the initial oil concentration was removed. Abiotic process reduced the diesel oil contamination to about 616 mg kgdry soil at the end of the experiment. Seven microcosms were set up to fulfill the experiments. The decontamination activity follow this order; Bacillus sp. H6 + A. flavus consortium > Bacillus sp. H6 > natural control > A. flavus > cycloheximide treated > benzyl Penicillin-Streptomycin treated > poisoned control. Gas chromatographic analysis data revealed that both A. flavus and Bacillus sp. H6 treatment led to complete utilization of carbon-17 compounds. Other biodegradation products such as C-15, 16, 20, 21, and 24 appears in the chromatogram after 150 days incubation. Increase of C-20, 21 and C-24 compounds also noticed. The fungaland bacterium consortium treatment depicted a decrease of all detected n-alkanes. The microbial success in biodegradation was evaluated by determining the number of germinating seeds of Phaseolus vulgaris. The highest level of germination (92 %) was detected in consortium microcosms after 150 days incubation. The treatment with A. flavus and Bacillus sp. H6 separately led to a lower percentage of germination (86%). The other treatments showed variable results except the poisoned control that showed negative germination and minor chemical degradation of diesel oil. Thus, bacterial-fungal consortium treatment is effective in bioremediation of contaminated oils than separate treatment.