Plant-based oil-sorbents harbor native microbial communities effective in spilled oil-bioremediation under nitrogen starvation and heavy metal-stresses

• Published in: Ecotoxicology and environmental safety Vol. 181; pp. 78 - 88
• Main Authors: Dashti, N., Ali, N., Khanafer, M., Radwan, S.S.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 15-10-2019
• Subjects: Bioremediation; Diazotrophs; Heavy metal-resistance; Hydrocarbonoclastic microorganisms; Oil sorbents; Oil sorbents; Bioremediation; Hydrocarbonoclastic microorganisms; Heavy metal-resistance; Diazotrophs
• ISSN: 0147-6513; 1090-2414
• DOI: 10.1016/j.ecoenv.2019.05.072

Cultivation on selective media revealed that the oil-sorbents, wheat straw, corncobs and sugarcane bagasse harbor hydrocarbonoclastic, diazotrophic and heavy metal-resistant microorganisms. Nitrogen-free media containing 1.0% crude oil lost between 32.2 and 37.5% of this oil, after 8 months when they have been inoculated with such microorganism-loaded sorbents. The used wheat straw, corncobs and sugarcane bagasse samples, 1.0 g each, absorbed respectively, 1.9, 1.1 and 2.5 g oil samples, and lost 24.3–39.2% of these amounts, after they had been incubated for 8 months. Total genomic DNA's from culture media and sorbents revealed various nitrogenase-coding nifH-genes. Pure hydrocarbonoclastic microbial isolates tolerated certain concentrations of, Hg2+, Cd2+, Pb2+, AsO43− and AsO33−. Some of those isolates even grew excellently with up to 1000 ppm of Pb2+ and 36,000 ppm of AsO43− also in the presence of oil. Tested strains removed the tested heavy metals, Hg2+, Cd2+ and Pb2+ from the media and thus, reduced their toxicity against the hydrocarbon-degraders. It was concluded that plant-based sorbents, not only remove oil physically, but also harbor microbial communities effective in spilled oil-bioremediation under multiple stresses. Although each community consisted of one to three species only, the consortia which reached in numbers millions of CFU ml−1 enrich the oily media with fixed nitrogen, and remove heavy metals which otherwise inhibit the oil-degrading microorganisms.
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•Microbial consortia in oil sorbents removed 32.2–37.5% of oil from nitrogen-free media in 8 months.•Genomic DNA extracts from those sorbents comprised several nifH-genes coding for N2-fixation.•Mercury resistant isolates contained merA-genes coding for Hg2+-resistance.•Bacteria and yeasts from those sorbents tolerated and removed heavy metals in the media.•Results contribute to proposing oil-bioremediation approach under multiple stresses.