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BIOREMEDIATION POTENTIAL OF INDIGENOUS BACTERIA AND FUNGI ISOLATED FROM CRUDE OIL-CONTAMINATED SOIL IN EDO STATE ON TOTAL PETROLEUM HYDROCARBONS.

CHAPTER ONE
INTRODUCTION

Background to the study.
The economy of Nigeria has been relying on crude oil exploration and production since the time when those comprise most of the government revenues and foreign exchange. Nonetheless, this industry has caused profound and chronic destruction of the environment in the Niger Delta region, including the Edo State which is a considerable component of it. The result of the caused oil spills caused by the failure of pipeline, sabotage, vandalism, corrosion of equipment, and illegal artisan refining activities have led to large pockets of contamination with total petroleum hydrocarbons (TPH) in soil and water bodies. These toxins make large regions of agricultural land non-productive, kill vegetation, decrease the levels of biodiversity, contaminate the resources of ground water, and place human populations at significant health risks, such as respiratory disorders, skin issues, loss of biodiversity, and possible carcinogenic effects (Omenna et al., 2023; Udinyiwe et al., 2022
In the Edo State, the oil bearing communities like Ologbo, Ikpoba-Okha Local Government Area, Benin City environs and Geregele River have been incessantly hit by crude oil pollution accidents. Such development has harmed farmlands, wetlands, and freshwater systems thus interfering with the livelihoods of the people who relied on fishing and farming as a source. TPH, which is a complex of polycyclic aromatic, aromatic and aliphatic hydrocarbons, is very persistent in the environment. It possesses low aqueous solubility, high hydrophobicity, and are resistant to chemical degradation, its low aqueous solubility, high hydrophobicity, and chemical recalcitrance interfere with natural attenuation processes and allow it to have toxic effects on soil microbiota, suppress plant growth, and bioaccumulate in the food chain (Ehis-Eriakha et al., In most affected locations within the Niger Delta, the levels of TPH remain in excess of regulatory limits as outlined by the Department of Petroleum Resources (now Nigerian Upstream Petroleum Regulatory Commission), and are as high as several thousand milligrams per kilogram of soil.
The traditional physical and chemical remediation techniques, including soil excavation and off-site disposal, incineration, soil washing, and chemical oxidation are commonly used. Yet, they tend to be too costly and energy-demanding, disturb disruptive of the ecosystem, and may produce secondary pollutants or un-completely degraded by-products. They are also not sustainable in resource-limited contexts such as Nigeria to scale to large applicabilities in large areas of contaminated land (Orikpete and Ewim, 2024; Adesipo et al., 2020).
An alternative method that has come out to be promising, sustainable, cost effective, and environmentally friendly is bioremediation. It uses the metabolic processes of microbes to convert or mineralise toxic hydrocarbons into less toxic substances, which, in the end, results in the generation of carbon dioxide, water and biomass. Especially beneficial are indigenous (native) bacteria and fungi isolated in chronically contaminated environments since they are already acclimated to the local climatic edaphic and contaminated environment. They have specialised enzyme pathways, such as alkane monoxygenases with aliphatic hydrocarbons and aromatic ring-hydroxylating dioxylases with polycyclic aromatic compounds, allowing them to effectively metabolise TPH (Omenna et al., 2023; Ibietela et al., 2022; Ehis-Eriakha et al.,
Recent researches carried out in the Niger delta and the southern region of the Nigeria state have reported the promising degradative behaviors of the locally isolated microbial isolates. The Ologbo and Benin regions of the Edo state isolated and characterised bacterial strains Lactobacillus fermentum, Lactobacillus nagelii, and Paenalcaligenes suwonesis in crude-oil-contaminated soils of these regions. They had a high tolerance to hydrocarbons, had high hydrophobic surface characteristics that facilitated their adhesion to oil droplets and had phylogenetic affiliations as favouring bioremediation. In the same vein, Udinyiwe et al. (2022) found that bacterial isolates obtained in crude oil contaminated soil samples in the Gelegele River in Edo state were able to significantly degrade TPH in the presence of crude oil as the sole carbon source in growing in mineral salt media. In the fungal community, the indigenous species that have been reported to be useful on hydrocarbon-contaminated soils in the area have been found to break down complex petroleum fractions, including recalcitrant aromatics, because of their compact hyphal networks and the production of extracellular enzymes like peroxidases and laccases (Tudararao-Aherobo & Mesogboriw
Moreover, biostimulation regimens which contain organic amendments (e.g., poultry manure, oil palm bunch ash or cow dung) have also been demonstrated to drastically boost the activity and abundance of indigenous hydrocarbonoclastic microbes. These amendments deliver restricting nutrients (nitrogen and phosphorus), enhance the soil aeration and water retention, and have accomplished TPH reductions of more than 88% in a period of 42 to 70 days with respect to laboratory and field gear conditions (Ibietala et al., 2022; Amajuoyi et al., 2022). All these reasons suggest that the overall bioremediation potential of the local adapted bacteria and fungi is high and extensive data on the joint use of bacterial and fungal consortia to increase the intensity of TPH degradation is still scarce in Edo State (Orikpete et al., 2024; Ehis-Eriakha et al., 2020).

1.2 Statement of the Problem.
Although the microbial bioremediation has been reported to be successful in different components of the Niger Delta, site-specific data concerning who, physiological properties, degradative potential, and synergistic relationship links of native bacteria and fungi directly isolated off crude-oil-contaminated soils in Edo State remains insufficient. The majority of the current remediation activities, in the state and in the communities around, still rely on traditional physical or chemical practices. Not only are expensive and logistically complex but also inefficient and unsustainable, such methods often cause further destruction of the soil structure, decreased fertility, and an ecological imbalance in the long term (Udinyiwe et al., 2022; Omenna et al., 2023).
In some communities in Edo State in oil-affected areas, the measured TPH ranges their concentrations significantly above the Department of Petroleum Resources intervention limit of 5,000 mg kg -1, and in some cases, the concentrations become so high as to make the soil biologically sterile and therefore unable to support agriculture. Even though indigenous microbial communities that could naturally degrade these hydrocarbons are found at these locations, they have not been isolated, characterised, and optimised to be used in bioremediation. Such unquenchable knowledge gap impedes the development and establishment of effective culturally acceptable and locally instigated strategies to bioremediate. As a result, the socio-economic stunts on the impacted host communities such as loss of livelihoods, food insecurity and health issues are prolonged (Orikpete and Ewim, 2024; Ehis-Eriakha et al., 2020).
An even greater untapped opportunity is the lack of research in bacterial-fungal consortia which may interact synergistically and potentially faster degradation speed and enhancement of the breakdown of a larger repertoire of hydrocarbon fractions than single cultures.

1.3.1 Aim

The aim of this study is to evaluate the bioremediation potential of indigenous bacteria and fungi isolated from crude oil-contaminated soil in Edo State on total petroleum hydrocarbons (TPH).

1.3.2 Specific Objectives

The specific objectives are to:

1. 1. Isolate and characterise indigenous bacteria and fungi from selected crude oil-contaminated sites in Edo State.
   2. Screen the isolates for their ability to utilise crude oil as the sole carbon source.
   3. Determine the TPH degradation efficiency of individual isolates and selected bacterial–fungal consortia under laboratory conditions.
   4. Assess the effect of the most efficient consortia on selected physicochemical properties of the contaminated soil.
   5. Identify the most promising microbial strains or consortia for possible field-scale bioremediation application in Edo State.

   1.4 Research Questions

   1. What are the predominant bacterial and fungal species that can be isolated and characterised from crude oil-contaminated soils in selected sites in Edo State?
   2. To what extent can these indigenous isolates utilise crude oil as the sole carbon source?
   3. How efficiently can the individual isolates and selected bacterial–fungal consortia degrade TPH in laboratory-scale experiments?
   4. To what extent do the most efficient microbial consortia improve the physicochemical properties of the polluted soil?
   5. Which microbial strains or consortia demonstrate the highest promise for potential application in bioremediation of crude oil-contaminated soils in Edo State?

1.5 Significance of the Study

This research will provide comprehensive documentation of the bioremediation potentials of bacteria and fungi native to Edo State crude-oil-polluted soils. The findings will enrich the national database on hydrocarbonoclastic microorganisms and support the development of indigenous, low-cost bioremediation technologies suited to local conditions. Policymakers, oil companies, and environmental agencies will gain evidence-based recommendations for sustainable remediation of oil-impacted sites, thereby lowering costs and advancing ecological restoration. The study will also contribute to knowledge on microbial ecology in the Niger Delta and serve as a valuable reference for future researchers and students in environmental microbiology and bioremediation (Orikpete & Ewim, 2024; Ehis-Eriakha et al., 2020).

1.6 Scope of the Study

The study focuses on the isolation, characterisation, and laboratory-scale evaluation of indigenous bacteria and fungi obtained from crude oil-contaminated soil samples collected from selected sites in Edo State (Ologbo, Benin, and Gelegele areas). TPH degradation will be assessed using standard laboratory microcosm setups with Escravos-blend crude oil as the contaminant. Field-scale application falls outside the scope of this work.

1.7 Limitations of the Study

The research is limited by laboratory resources and the typical 6–12-month timeframe for such projects. While efforts will be made to simulate field conditions, results from controlled microcosms may not fully replicate in-situ performance due to variables such as fluctuating temperature, moisture, and nutrient levels. Molecular confirmation of all isolates may also be constrained by sequencing costs.

1.8 Definition of Terms

Bioremediation: The use of living organisms, primarily microorganisms, to degrade or detoxify environmental pollutants.

Indigenous microorganisms: Microbes that are native to and naturally occurring in the contaminated site under study.

Total Petroleum Hydrocarbons (TPH): The sum of all petroleum-derived hydrocarbons measurable in a soil sample.

Crude oil-contaminated soil: Soil whose physicochemical and biological properties have been altered by the introduction of crude petroleum.

REFERENCES Adesipo, A. A., et al. (2020). Prospects of in-situ remediation of crude oil contaminated lands in Nigeria. Environmental Technology & Innovation, 20, Article 101120. https://doi.org/10.1016/j.eti.2020.101120

Amajuoyi, C. A., Akani, N. P., & Wemedo, S. A. (2022). Comparative study on the performance of oil palm bunch ash and poultry manure as nutrient supplements in bioremediation of crude oil polluted soil. International Journal of Current Microbiology and Applied Sciences, 11(2), 220–238.

Ehis-Eriakha, C. B., Chikere, C. B., & Akaranta, O. (2020). Functional gene diversity of selected indigenous hydrocarbon-degrading bacteria in aged crude oil. International Journal of Microbiology, 2020, Article 2141209. https://doi.org/10.1155/2020/2141209

Ibietela, D. S., Ugboma, C. J., & Onwukwe, J. O. (2022). Bioremediation of total petroleum hydrocarbon polluted soil from an abandoned illegal crude oil refining site using organic amendments. Acta Scientific Microbiology, 5(1), 70–79.

Omenna, E. C., Omage, K., Ezaka, E., & Azeke, M. A. (2023). Tolerance, taxonomic and phylogenetic studies of some bacterial isolates involved in bioremediation of crude oil polluted soil in the southern region of Nigeria. Heliyon, 9(4), Article e15639. https://doi.org/10.1016/j.heliyon.2023.e15639

Orikpete, O. F., & Ewim, D. R. E. (2024). Microbial bioremediation of petroleum contamination in the Niger Delta: Assessing the role of indigenous microbial communities and potential for sustainable restoration. In Microbial bioremediation and multiomics technologies for sustainable development (pp. 96–125). Royal Society of Chemistry. https://doi.org/10.1039/BK9781837673131-00096

Tudararao-Aherobo, L., & Mesogboriwon, S. (2020). Bioremediation of spent engine oil contaminated soils using indigenous fungi species. International Journal of Scientific Research in Science and Technology, 7(2), 1–10.

Udinyiwe, C. O., Idemudia, I. B., & Ekhaise, F. O. (2022). Biodegradation potential of bacterial isolates from crude oil contaminated soil samples from Gelegele River, Edo State. NIPES Journal of Science and Technology Research, 4(1), 1–12.