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Optimization of bioremediation-cocktail for application in the eco-recovery of crude oil polluted soil.

ABSTRACT: Background: Environmental sustainability is the driver for finding the optimal bioremediation cocktail with the combination of highly potent hydrocarbonoclastic strains and the nutrient additives that significantly enhance mineralization of crude oil in polluted soil in order to mitigate its deleterious effects on the environment. In this study, four hydrocarbon-degrading bacterial strains were pre-selected from mined rhizobacterial isolates in aged crude oil-contaminated soil. Method: Agrowaste residues of poultry-droppings, corn chaff, and plantain peel were selected among others for their ability to support high biomass of selected bacterial strains. Baseline proximate analysis was performed on the agrowaste residues. Simplified, one variable at a time (OVAT) was employed in the validation of the variables for optimization using the Multivariate analysis tool of Response Surface Methodology (RSM). To test the significant formulation variables, the Box-Behnken approach using 15 runs design was adopted. Results: The rate of contaminant removal was observed to fit into a quadratic function. For optimal rate or contaminant removal, the fitted model predicted the optimal formulation cocktail condition to be within 0.54 mg/kg (Corn steep liquor), phosphate 137.49 mg/kg (poultry droppings) and 6.4% inocula for initial TPH of 9744 mg kg -1 and THC of 9641 mg kg -1 contaminant level. The model for the application of the bioremediation product and the variables evaluated had a significant p-value < 0.005 for the attainment of 85 to 96 % of TPH and THC removal after 56 days of treatment. Conclusions: This study has shown the need to harness the abundant agrowaste nutrients in supporting high throughput rhizobacteria in the formulation of a bioremediation agent suitable for use in the reclamation of oil spill sites in the Niger Delta oil-producing region.

SUBMITTER: Agbaji JE

PROVIDER: S-EPMC7551562 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Optimization of bioremediation-cocktail for application in the eco-recovery of crude oil polluted soil.

Agbaji Joseph E JE Nwaichi Eucharia O EO Abu Gideon O GO

AAS open research 20200422

<b>Background</b>: Environmental sustainability is the driver for finding the optimal bioremediation cocktail with the combination of highly potent hydrocarbonoclastic strains and the nutrient additives that significantly enhance mineralization of crude oil in polluted soil in order to mitigate its deleterious effects on the environment. In this study, four hydrocarbon-degrading bacterial strains were pre-selected from mined rhizobacterial isolates in aged crude oil-contaminated soil. <b> Method ...[more]

PMID: 33094269

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Project description:Indigenous bacteria play vital roles in the bioremediation of crude oil polluted soils. The effectiveness of the bioremediation process depends on the tolerance, characteristics and biodiversity of the bacteria isolates. Bacteria strains were isolated from crude-oil polluted sites in different locations in the southern region of Nigeria namely: Azikoro and Otukpoti (Bayelsa state); Ologbo and Benin (Edo State) and non-polluted soil was collected from Ibadan (Oyo state). Tolerance study was conducted for 96 h s. Isolation and characterization of the most effective isolate from each location was done using cultural, physico-chemical and molecular methods. The tolerance level of the isolates from the different oil-polluted soils and their comparative growth performance on crude oil supplemented media decreases in the order: Azikoro - Ologbo - Otukpoti - Benin. MATS analysis showed that cell surfaces of Azikoro, Ologbo and Otukpoti strains exhibited 58-63 % adhesion to n-hexadecane and are hydrophobic strains while Benin strain possess 38% adhesion to n-hexadecane and are hydrophilic. The cell surfaces of isolates from Azikoro, Ologbo and Otukpoti are highly Lewis-acidic while that from Benin is highly Lewis-basic. Isolates from Benin-3, Ologbo-1, and Otukpoti-1 were shown to be gram positive while that from Azikoro was gram negative. 16S rDNA fingerprinting confirmed the identities of the isolates as follows: Paenalcaligenes suwonesis with accession numbers NR-133804.1 from Azikoro spillage site (93.77%); Lactobacillus nagelii with accession number NR-158108.1 (91.30%) from Benin spillage site; Lactobacillus fermentum with accession number NR-104927.1 (96.70%) from Ologbo and Otukpoti spillage sites. Phylogenetic analysis putatively categorized the isolates from Otukpoti and Ologbo in close association belonging to same homology while Benin isolate is a subgroup. The characteristics and biodiversity of all the isolated bacteria from the regions possibly justifies their involvement in the bioremediation of petroleum hydrocarbons.

Project description:Fungi have increased tolerance to environmental stress (also related to the access of pollutants, e.g., trace elements and polycyclic aromatic hydrocarbons PAHs). The aim of the study was to evaluate the mycobiome and functional diversity of fungi in long-term crude-oil contaminated soils as the potential bioremediators of oil contaminated sites. Samples were taken from three historical oil wells (over a century old) at two distances: within a 0.5 m radius of the oil wells (OWP1, OWP2, and OWP3) and within a 3 m radius from the oil wells as the controls (OW1, OW2, and OW3). Next generation sequencing (for the ITS region) was accompanied with determination of the functional fungal community based on Biolog FFPlates, glomalin related soil protein (GRSP) content, trace element and PAHs concentration. The research hypothesis assumed that long-term natural bioremediation of crude oil contaminated soils can contribute to intensive development of a unique fungal community adapted to the contamination conditions. The identification of such fungi can be of particular importance in soil bioremediation. There were significant differences in the fungal community and functional diversity between the soil samples. The soils collected directly from the oil wells were characterized by higher biological activity and higher diversity of PAH-degrading fungal candidates compared to the soils collected within 3 m of the oil wells. The total glomalin-related soil proteins (T-GRSP) and easily-extractable glomalin-related soil proteins (EE-GRSP) contents were lower in soil samples taken directly from the crude oil well. The control soil (OW) subjected to a long-term natural remediation may already have sufficient conditions for the growth and development of mycorrhizal fungi. The mycobiome of the soils collected directly from the oil wells (OWP1, OWP2, and OWP3) was characterized by a 35% share of PAH-degrading candidates, compared to the soil collected at the 3 m distance from the oil wells (OW1, OW2, and OW3) at < 5%. The main PAH-degrading fungal candidates belong to genera Ilyonectria, Chaetomium, Gibberella, Paraphoma, Schizothecium, Pseudorobillarda, Tetracladium, Ganoderma, Cadophora, Exophiala, Knufia, Mycoleptodiscus, Cyphellophora, Fusicolla, Devriesia, Didymella, Plenodomus, Pyrenochaetopsis, Symbiotaphrina, Phallus, Coprinellus, Plectosphaerella, Septoriella, and Hypholoma. The share of three- and four-ringed PAHs in soil was higher as the distance from the oil well increased. These results may indicate that more effective degradation processes occur closer to the oil wells.

Project description:Crude oil pollution of soil is a serious environmental issue, and bioremediation using plants and microorganisms is a natural and sustainable method for its restoration. Pot incubation of a two-factor randomized block (plants with two levels, and crude oil with three levels) was designed to investigate the rhizosphere bacterial community of Suaeda salsa (L.) Pall. Crude oil contamination of soil was studied at different levels: 2 g/kg (low), 4 g/kg (medium), and 6 g/kg (high) levels. In this study, the physicochemical properties of the collected rhizosphere soil were analyzed. Moreover, the soil bacteria were further identified using the 16S rRNA gene. The effects of S. salsa and crude oil and their interaction on the physiochemical properties of the soil and crude oil degradation were found to be significant. Crude oil significantly influenced the diversity and evenness of bacteria, while the effects of S. salsa and interaction with crude oil were not significant. Proteobacteria were found to be dominant at the phylum level. Meanwhile, at the genera level, Saccharibacteria and Alcanivorax increased significantly in the low and medium contamination treatment groups with S. salsa, whereas Saccharibacteria and Desulfuromonas were prevalent in the high contamination treatment group. High crude oil contamination led to a significant decrease in the bacterial diversity in soil, while the effects of S. salsa and its interaction were not significant. Despite the highest abundance of crude oil degradation bacteria, S. salsa reduced crude oil degradation bacteria and increased bacteria related to sulfur, phosphorus, and nitrogen cycling in the low and high contamination group, whereas the opposite effect was observed for the medium contamination treatment group. The abundance of most crude oil degradation bacteria is negatively correlated with crude oil content. Nitrogen cycling bacteria are sensitive to the total nitrogen, total phosphorus, ammonia nitrogen, and nitrate nitrogen, and pH of the soil. Sulfur cycling bacteria are sensitive to aromatic hydrocarbons, saturated hydrocarbons, and asphaltene in soil. This research is helpful for further studying the mechanism of synergistic degradation by S. salsa and bacteria.

Dataset Information

Optimization of bioremediation-cocktail for application in the eco-recovery of crude oil polluted soil.

Publications

Optimization of bioremediation-cocktail for application in the eco-recovery of crude oil polluted soil.

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