Comparison of Native Bacterial and Fungal Bioaugmentation in the Removal of Petroleum from Soil in the Presence of Sorghum

Petroleum pollution has become an environmental menace in oil-rich countries. Bioremediation can be used as an environmental-friendly method to remove pollutants. We investigated the effects of bioaugmentation, phytoremediation, and bioaugmented phytoremediation strategies to remove petroleum. The petroleum-degrading bacteria ( Brachybacterium muris and Micrococcus yunnanensis ) and fungi ( Aspergillus niger and Aspergillus sp.) were isolated from petroleum-polluted soil. A factorial experiment was performed in a completely randomized design with three replications. Factors include three levels of petroleum (0,4 and 8% w/w), two phytoremediation treatments (without plants and sorghum), and five bioaugmentation treatments (without microorganism, B. muris , M. yunnanensis, A. niger and A. sp). The efficiency of petroleum removal strategies at 4% level is as follows: bioaugmented phytoremediation > bacteria > phytoremediation > fungi. But at 8%, it decreased in the following order: bioaugmented phytoremediation > fungi > phytoremediation > bacteria. A. niger + sorghum(90.06%) was stronger in removing petroleum. at the level of 8%, treatments of B. muris, M. yunnanensis , A. niger and A. sp. increased dry weight about 1.70-, 2.15-, 3.76-, and 2.92-fold the treatment of without microorganisms, respectively. At 4%, the activities of dehydrogenase (16.67 ± 0.52), arylsulfatase (0.81 ± 0.02), and lipase (11.94 ± 0.23) were the highest in the treatment of M. yunnanensis , and at the 8%, their activities were about 7.40 ± 0.27, 0.70 ± 0.01, and 5.86 ± 0.65 in the treatment of A. niger , respectively. The synergistic relationship of sorghum with fungi (especially A. niger ) was more efficient than bacteria in removing petroleum and biological characteristics (enzymes, respiration, and biomass). Higher peroxidase and catalase activities were observed in treatment of 8% + A. niger (6.81 ± 0.07) and 8% + A. sp (5.87 ± 0.08), respectively. Simultaneous application the fungi ( A. niger ) and sorghum can be suitable candidates for the remediation of petroleum, and increase tolerance of sorghum to petroleum stress.