Oil-polluted Soil Research Articles

From Killer to Solution: Evaluating Bioremediation Strategies on Microbial Diversity in Crude Oil-Contaminated Soil over Three to Six Months in Port Harcourt, Nigeria

The study aimed to evaluate the efficacy of various bioremediation approaches on microbial diversity in crude oil-contaminated soil over three to six months in Port Harcourt, Nigeria. The objective was to assess the impact of different bioremediation strategies on microbial populations, particularly focusing on hydrocarbon-utilizing bacteria and fungi. Microbial populations were quantified using serial dilution and microbial count techniques. The vapor phase transfer mechanism was employed to estimate hydrocarbon-utilizing bacteria and fungi. Bacterial and fungal colonies were incubated for five days, followed by biochemical tests for isolate identification. Fungal pure cultures were observed under a microscope. The study observed a significant increase in microbial populations in soil free of crude oil pollution when bioremediators such as mushrooms and earthworms were introduced. Mushrooms exhibited a 50% increase in hydrocarbon-utilizing bacteria (HUB), while earthworms showed a 55% increase in HUB over the three to six-month period. The longer lifespan and nutrient absorption capabilities of earthworms facilitated faster growth. Furthermore, significant growth in the microbial population of hydrocarbon-utilizing bacteria and fungi was observed in crude oil-polluted soil after employing bioremediation, with the highest growth observed in soil treated with mushrooms at six months, followed by earthworms at six months. Conversely, the lowest microbial population was recorded in soil polluted with 10% crude oil and remediated with earthworms at three months. The results suggest that mushrooms and earthworms effectively increase microbial populations in crude oil-polluted soil. However, mushrooms demonstrated a higher microbial population increase compared to earthworms, especially in terms of promoting the growth of hydrocarbon-utilizing bacteria (HUB) and hydrocarbon-utilizing fungi (HUF). Based on the findings, it is recommended to prioritize using mushrooms as bioremediation agents in similar environmental restoration efforts due to their superior efficacy in increasing microbial populations, particularly HUB and HUF. This study underscores the potential of mushrooms and earthworms as effective bioremediation agents for restoring microbial diversity in crude oil-contaminated soil, offering insights for sustainable environmental restoration practices in oil-affected regions like Port Harcourt, Nigeria.

Evaluating effect of aeration and sand addition on soil physicochemical properties and soil total petroleum hydrocarbon bioremediation efficiency by indigenous isolated bacteria

In line with different investigations for bioremediation of oil-polluted soil at the global scale, the present study designed new insight about qualified physicochemical properties along with bioremediation of oil-polluted soil. The principle of presented bioremediation technique of oil-polluted soil in the present study was a combination of physical and biological procedure for the remediation of oil-polluted soils. The study investigates the impact of aeration and sand addition on bioremediation efficiency of two types oil-polluted soil with different ages of oil pollution. The experiment involves isolating and identifying indigenous bacteria, preparing the inoculum, and inoculating it into oil-contaminated soils. The physical and chemical properties of the soil samples were analyzed, and total petroleum hydrocarbon (TPH) levels were assessed before and after the bioremediation period followed by sand addition and air-forced soil aeration. The achieved results from laboratory-scale investigation show about 80% in soil TPH decreasing followed by sand addition and aeration for two types of fresh and aged polluted soils, while TPH decreasing in soil without sand addition and aeration was about 48% from studied soils. The findings of the present study can be utilized as parametric investigation in designing bioreactors of oil-polluted soil bioremediation purposes.

Isolation, Screening and Identification of Biosurfactant Producing Strain Nocardiopsis dassonvillei var B2 From Oil Contaminated Soil.

Petroleum and other oil manufacturing industries contribute to environmental pollution by releasing hazardous hydrocarbons. Biosurfactants offer a sustainable solution for mitigating oil pollution through emulsification processes, safeguarding agricultural soils, aquatic ecosystems, and human health. This study focuses on isolating, screening, and identifying actinomycetes producing biosurfactant from oil-polluted soil in the naval dockyard of Visakhapatnam. Biosurfactant production was successfully achieved utilizing Kim's medium, which was supplemented with olive oil serving as the carbon source. The evaluation involved preliminary identification tests, including oil displacement, Parafilm-M, and lipase activity assays, using sodium lauryl sulfate as the standard reference. Surface tension and emulsification index measurements were conducted, and the chemical composition of glycolipids and phospholipids was elucidated using phenol-sulfuric acid and phosphate assays. Glycolipids, specifically identified as rhamnolipids, were confirmed via cetyltrimethylammonium bromide (CTAB) testing and quantitatively analyzed using the orcinol method. The cell-free broth exhibited antagonistic activity against Gram-positive and negative bacilli.16S rRNA sequencing-based phylogenetic analysis was carried out by the NCIM, Pune, with the gene sequence being deposited in GenBank. Further characterization of isolate B2 included scanning electron microscopy (SEM) analysis, as well as physiological and biochemical assays. This study highlights the ability of Nocardiopsis dassonvillei var. B2, isolated from oil-polluted soil, to produce biosurfactants, specifically glycolipids identified as rhamnolipids. Our findings represent the first reported instance of biosurfactant production from isolate B2 originating from the naval dockyard in Visakhapatnam, Andhra Pradesh, India.

Bioremediation petroleum wastewater and oil-polluted soils by the non-toxigenic indigenous fungi.

Soil and wastewater samples contaminated by petroleum-related industries were collected from various locations in Saudi Arabia, a country known for its vast oil reserves. The samples were analyzed for their physicochemical properties, including the presence of metals, petroleum hydrocarbons, and aromatic compounds. A total of 264 fungal isolates were analyzed and categorized into eight groups of Aspergillus (194 isolates) and four groups of Penicillium (70 isolates). The potential of these fungal groups to grow in oil or its derivatives was investigated. Two isolates, Aspergillus tubingensis FA-KSU5 and A. niger FU-KSU69, were utilized in two remediation experiments-one targeting wastewater and the other focusing on polluted soil. The FA-KSU5 strain demonstrated complete removal of Fe3+, As3+, Cr6+, Zn2+, Mn2+, Cu2+ and Cd2+, with bioremediation efficiency for petroleum hydrocarbons in the wastewater from these sites ranging between 90.80 and 98.58%. Additionally, the FU-KSU69 strain achieved up to 100% reduction of Co2+, Ba2+, B3+, V+, Ni2+, Pb2+ and Hg2+, with removal efficiency ranging from 93.17 to 96.02% for aromatic hydrocarbons after 180min of wastewater treatment. After 21days of soil incubation with Aspergillus tubingensis FA-KSU5, there was a 93.15% to 98.48% reduction in total petroleum hydrocarbons (TPHs) and an 88.11% to 97.31% decrease in polycyclic aromatic hydrocarbons (PAHs). This strain exhibited the highest removal rates for Cd2+ and As3+ followed by Fe3+, Zn2+, Cr6+, Se4+ and Cu2+. Aspergillus niger FU-KSU69 achieved a 90.37% to 94.90% reduction in TPHs and a 95.13% to 98.15% decrease in PAHs, with significant removal of Ni2+, Pb2+ and Hg2+, followed by Co2+, V+, Ba2+ and B3+. The enzymatic activity in the treated soils increased by 1.54- to 3.57-fold compared to the polluted soil. Although the mixture of wastewater and polluted soil exhibited high cytotoxicity against normal human cell lines, following mycoremediation, all treated soils and effluents with the dead fungal biomass showed no toxicity against normal human cell lines at concentrations up to 500 µL/mL, with IC50 values ≥ 1000 µL/mL. SEM and IR analysis revealed morphological and biochemical alterations in the biomass of A. tubingensis FA-KSU5 and A. niger FA-KSU69 when exposed to petroleum effluents. This study successfully introduces non-toxigenic and environmentally friendly fungal strains play a crucial role in the bioremediation of contaminated environments. Both strains serve as low-cost and effective adsorbents for bio-remediating petroleum wastewater and oil-contaminated soil. Heavy metals and hydrocarbons, the primary pollutants, were either completely removed or reduced to permissible levels according to international guidelines using the dead biomass of FA-KSU5 and FA-KSU69 fungi. Consequently, the environments associated with this globally significant industry are rendered biologically safe, particularly for humans, as evidenced by the absence of cytotoxicity in samples treated with A. tubingensis FA-KSU5 and A. niger FA-KSU69 on various human cell types.

Surfactant-Based Chemical Washing to Remediate Oil-Contaminated Soil: The State of Knowledge.

As the energy demand increases, there is a significant expansion and utilization of oil resources, resulting in the inevitable occurrence of environmental pollution. Oil has been identified as a prevalent soil contaminant, posing substantial risks to the soil ecosystems. The remediation of soil contaminated with oil is a formidable undertaking. Increasing evidence shows that chemical washing, a remediation technique employing chemical reagents like surfactants to augment the solubilization, desorption, and separation of petroleum hydrocarbons in soil, proves to be an efficacious approach, but the latest advances on this topic have not been systematically reviewed. Here, we present the state of knowledge about the surfactant-based chemical washing to remediate oil-contaminated soil. Using the latest data, the present article systematically summarizes the advancements on ex situ chemical washing of oil pollution and provides a concise summary of the underlying principles. The use of various surfactants in chemical washing and the factors influencing remediation efficiency are highlighted. Based on the current research status and knowledge gaps, future perspectives are proposed to facilitate chemical washing of oil-polluted soil. This review can help recognize the application of chemical washing in the remediation of oil-polluted soil.

Nitrogen utilization efficiency assessment during bioremediation of petroleum-contaminated loess soils: insights from metagenomic analysis

Nitrogen addition is commonly used to remediate total petroleum hydrocarbons (TPH) in petroleum-contaminated soils. However, acceptable exogenous nitrogen dosages and their utilization efficiency for the degradation of hydrocarbons in oil-polluted soils are not well understood. This study compared the hydrocarbon bioremediation capacity by applying different doses of NH4Cl as a stimulant in soils contaminated with TPH at 8553 and 17090 mg/kg. The results showed acceptable exogenous nitrogen levels ranging from 60 to 360 mg N/kg soil, and the optimal nitrogen dosage for TPH remediation was 136 mg N/kg in soils with different TPH concentrations. The nitrogen availability efficiency (NAE) and nitrogen polarization factor availability (NPFA) in the 136 mg N/kg addition treatments were 6.69 and 20.47 mg/mg in 8533 mg/kg TPH-polluted soil, and 6.03 and 31.11 mg/mg in 17090 mg/kg TPH-polluted soil, respectively. Metagenomic analysis revealed that the application of 136 mg/kg nitrogen facilitated ammonia oxidation and nitrite reduction to nitric oxide, and induced soil microorganisms to undergo regulatory or adaptive changes in energy supply and metabolic state, which could aid in restoring the ecological functions of petroleum-contaminated soils. These findings underscore that 136 mg/kg of nitrogen dosage application is optimal for remediation of petroleum-contaminated soils irrespective of the TPH concentrations. This exogenous nitrogen application dosage for TPH remediation aligns with the nitrogen requirements for crop growth in agriculture.

Molecular identification of biosurfactant-producing bacteria obtained from oil-polluted soil samples in Abakaliki, Ebonyi State, Nigeria

Several human activities have led to environmental pollution with crude oil and other related hydrocarbons. There are various technologies of remediating oil-polluted environments, but the use of biological agents such as biosurfactants are widely practiced, and are generally considered as safe and eco-friendly. This study aimed at isolating and identifying biosurfactant-producing bacteria obtained from oil polluted soil samples in Abakaliki, Ebonyi State, Nigeria using molecular techniques. Six waste oil-contaminated soil samples were collected from mechanic and generator repair workshops, and were analyzed using standard microbiological methods. Nine bacterial isolates were obtained from the waste oil-contaminated soil samples, and were suspected to be Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus. Molecular identification of the biosurfactant-producing isolates was also carried out using PCR and the genes responsible for biosurfactant production targeted. Oil spreading technique was used to detect the oil displacement activity (ODA) of the isolates. The emulsification index (E24) was calculated and the ability of the extracted biosurfactant to emulsify the hydrocarbons was determined. Pseudomonas aeruginosa had the highest ODA of 28.1 cm while Staphylococcus aureus had the least ODA of 5 cm. Pseudomonas aeruginosa showed E24 of 70.1%, Bacillus subtilis 57.1% while S. aureus showed 32.5%. Hence, Pseudomonas and Bacillus species have good potentials for biosurfactant production, and can be harnessed and utilized in the cleanup of oil polluted soil.

Remediation of oil-polluted soil using anionic and non-ionic composite biosurfactants

ABSTRACT Petroleum hydrocarbons as pervasive pollutants pose a significant threat to soil ecology and human health. Surfactant washing as an established technique can effectively remediate soils contaminated by hydrocarbons. Biosurfactants, which combine the properties of surfactants and environmental compatibility, have attracted increasing interest. However, due to the high production cost of biosurfactants, their practical application is restricted. This study addressed these limitations by selecting two biosurfactants, β-cyclodextrin (C1) and sodium carboxymethyl cellulose (C2), and developed a promising cleaning agent formula through compounding and the addition of suitable additives. When the volume ratio of C1 to C2 was 8:2 and an 8 g/L mixture of sodium humate and sodium carbonate electrolyte was added, the surfactant system’s surface tension reached a minimum, yielding optimal oil removal. The formation and synergistic behaviour of mixed micelles of surfactants were explained using ideal solution theory and the Rubingh model. By optimising the oil washing process parameters – normal temperature of 25 °C, pH 11, washing time of 2 h, solid–liquid ratio of 1:5, and oscillation frequency of 200 r/min – the oil removal rate achieved 76%. This cleaning agent, characterised by low production cost, straightforward application, environmental compatibility, and rapid, significant cleaning effect, shows potential for field-scale purification of petroleum-contaminated soil.

Assessing the Potential of Parkia biglobosa (Jacq.) R.Br. ex. G. Don - A Leguminous Plant Species commonly found in Nigeria to Decontaminate Crude Oil-polluted Soil in Terrestrial Ecosystem

The potentials of Parkia biglobosa (a leguminous plant species) to decontaminated crude oil-polluted soil in terrestrial ecosystem was evaluated in this study using appropriate standard techniques to estimate seedling germination, height, collar diameter, number of leaves and physicochemical characteristics (organic matter, pH, calcium, magnesium and sodium, nitrogen, phosphorous and potassium) of soil used, were determined using standard protocols. Results indicated that varying concentration of crude oil influenced the variables measured. For 0 ml, 25 ml, 50 ml, 75 ml and 100 ml crude oil treatments, Parkia biglobosa had 18%, 18%, 16%, 13% and 11% germination rate correspondingly; mean height of 38.70cm, 26.80cm, 21.20cm, 18.50cm and 6.80cm respectively, mean collar diameter of 0.32mm, 0.30mm, 0.26mm, 0.24mm and 0.22mm respectively; 2, 0, 0, 0 and 0 nodules count respectively, and 8.00, 6.00, 5.00, 5.00 and 2.00 leaf count respectively. All physicochemical parameters measured decreased in the soil in inverse proportion to crude oil concentration. So also, seedling germination, height, collar diameter, number of leaves and nodulation decreased in inverse proportion to crude oil concentration. Parkia biglobosa grew tolerably in both high and low concentrations of crude oil, which is an indication of its able to withstand crude oil toxicity. Parkia biglobosa as a nitrogen fixing plant would be a good candidate for the terrestrial restoration of crude oil contaminated regions in Nigerian.

Exophiala chapopotensis sp. nov., an extremotolerant black yeast from an oil-polluted soil in Mexico; phylophenetic approach to species hypothesis in the Herpotrichiellaceae family.

Exophiala is a black fungi of the family Herpotrichiellaceae that can be found in a wide range of environments like soil, water and the human body as potential opportunistic pathogen. Some species are known to be extremophiles, thriving in harsh conditions such as deserts, glaciers, and polluted habitats. The identification of novel Exophiala species across diverse environments underlines the remarkable biodiversity within the genus. However, its classification using traditional phenotypic and phylogenetic analyses has posed a challenges. Here we describe a novel taxon, Exophiala chapopotensis sp. nov., strain LBMH1013, isolated from oil-polluted soil in Mexico, delimited according to combined morphological, molecular, evolutionary and statistics criteria. This species possesses the characteristic dark mycelia growing on PDA and tends to be darker in the presence of hydrocarbons. Its growth is dual with both yeast-like and hyphal forms. LBMH1013 differs from closely related species such as E. nidicola due to its larger aseptate conidia and could be distinguished from E. dermatitidis and E. heteromorpha by its inability to thrive above 37°C or 10% of NaCl. A comprehensive genomic analyses using up-to-date overall genome relatedness indices, several multigene phylogenies and molecular evolutionary analyzes using Bayesian speciation models, further validate its species-specific transition from all current Exophiala/Capronia species. Additionally, we applied the phylophenetic conceptual framework to delineate the species-specific hypothesis in order to incorporate this proposal within an integrative taxonomic framework. We believe that this approach to delimit fungal species will also be useful to our peers.

Molecular characterization of biosurfactant-producing bacteria from a crude oil polluted soil in Nigeria

Most biosurfactant-producing microorganisms are hydrocarbon degraders. The research was conducted to isolate and characterize biosurfactant-producing bacteria from a crude oil polluted soil in Nigeria. Biosurfactant-producing bacteria were isolated from crude oil-polluted soil. Crude oil-polluted soil was collected by random sampling and its physicochemical analysis was done. Bacteria were isolated from the contaminated soil and screened for biosurfactant production. Organisms that showed the ability to produce biosurfactant were identified using morphological, biochemical and molecular methods. The physicochemical parameters of the soil showed a pH 6.9, electrical conductivity of 71.5, 2.55% carbon, 2.016% nitrogen and 5.98% phosphorus. The values of biosurfactant tests showed that organisms S2 and S13 were positive for biosurfactant production. The percentage emulsion indexes of the two selected organisms S2 and S13 were 59.09% and 57.14% respectively. The Blast analysis from the molecular identification showed that the isolated organisms were Gordonia alkanivorans for S2 and Tsukamurella inochensis for S13. This research showed that the isolated biosurfactant-producing bacteria are abundant in the crude oil polluted soil.

Effect of heat-stable biocatalytic remediation cocktail (HBRC) on selected heavy metals present in crude oil-polluted soil

This study investigated the effect of a heat-stable biocatalytic remediation cocktail (HBRC) on selected heavy metals present in crude oil-polluted soil. The soil sample was collected from Agbura Community, Yenagoa, Bayelsa State. Heat-stable biocatalytic remediation cocktail (HBRC) also called garbage enzyme (GE) was produced from three substances; water, fruits skin (orange, pineapple, plantain, watermelon and banana peels) and brown sugar in a ratio of 10: 3: 1, and were allowed to ferment for 90 days. The soil sample was divided into six Groups (1 - 6). Groups 1 and 2 served as control; (unpolluted) and (polluted but not treated soil) while Groups 3 to 6 were given different treatments. The samples were prepared and selected heavy metals (Fe, Cu, Zn and Co) concentrations were analyzed using Atomic Absorption Spectrophotometer (AAS). After treatment of the crude oil-polluted soil with the HBRC for 180, there were significant reductions in Fe, Cu, Zn and Co were observed in Groups 3, 4, 5 and 6 when compared to Groups 1 and 2. The highest iron concentration reduction was observed in Group 3 (76.58%). Similarly, the highest Cu concentration reduction was seen in Group 5 (73.55%). Also, the highest Zn concentration reduction was observed in Group 6 (86.30%) while Co highest concentration reduction was seen in Group 5 (86.56%). Hence, the result reveals that HBRC can be used as a remediation cocktail for heavy metals.

Comparative Assessment of the Activities of Acid and Alkaline Phosphatases in Spent Crankcase Oil-Polluted Soil Ecosystem

Assessment of the level of contamination from possible impact of spent crankcase oil on soil ecosystem is imperative for the determination of environmental acceptability. This study investigated this impact ex-situ using a culture-dependent approach to evaluate the total microbial counts; biochemical and physicochemical tools to determine the activities of their exudates (acid and alkaline phosphatases), total petroleum hydrocarbon (TPH) and pH as indices. The experiment demonstrated that at 1.5 – 3.5% contamination across days-zero to -28, spent crankcase oil stimulated significantly (p<0.05) the activity of alkaline phosphatase in a concentration and time dependent manner from 4.0 ± 0.03 to 8.0 ± 0.00Katal. Acid phosphatase suffered inhibition significantly (p<0.05) from 6.0 ± 0.05 to 2.8 ± 0.01Katal. The contamination significantly (p<0.05) increased the total petroleum hydrocarbon (TPH) across all the days relative to control and this lowered the pH from 5.9 ± 0.00 to 4.8 ± 0.00. An initial reduction in microbial biomass from 1.32 x 109 ± 0.00 to 3.48 x108 ± 0.00 cfu/g on week one, and induction of hydrocarbon-degrading organisms, (the hydrocarbonclastics), to 3.7 x 10¬¬8 ± 0.10cfu/g at 1.5 – 3.5% contamination overtime correlated with enzyme induction, and activity. Ecosystem dynamics and mineralization were impaired and disrupted and the entire soil biochemistry was altered.

Short-term Effects of Crude Oil-polluted Soil on the Histomorphometry of the Femoral Cortex

Abstract Introduction: Skeletal remains are crucial in most forensic case investigations. There is therefore need to study the process of bone degradation and distortion caused by environmental factors. The aim of the study is to determine the effect of burial in a crude oil-polluted soil on long bone histomorphometry. Materials and Methods: Fragments of 1-cm diameter sections of the mid-shaft of the femur were obtained from a cadaver and divided into three groups. Group A fragments were not buried (control), Group B fragments were buried in normal clay soil, and Group C fragments were buried in crude oil-polluted soil. The bone fragments were buried for a period of 5 weeks in a crude oil-polluted soil and normal soil of pH 5.30 and 5.75, respectively. Histological sections of the bones were prepared using the modified Frost’s method of bone preparation. Photomicrographs were taken using a Leica ICC50E photomicroscope at four different regions of the slides. An ImageJ software was utilized to analyze the micrographic details. Results: Quantitative analysis showed a reduction in the Haversian canal area (HCA) and Haversian canal diameter (HCD) in the samples of bone fragments buried in the crude oil-polluted soil compared to the control. The crude oil-polluted soil showed a mean HCA and HCD of 83.52 μm and 8.91 μm as against 153.23 μm and 16.01 μm for the control. There was no statistically significant difference (P > 0.05) in HCA and HCD between the control bones and those buried in normal and crude oil-polluted soil. The variation in number of osteons was observed to be nonstatistically significant for both bone samples exposed to crude oil and those not exposed. Conclusion: The result of this study shows that crude oil-polluted soil have little or no effects on bone histomorphometry for a short period of time. This should help guide forensic investigations.

Bioremediation of Oil-Polluted Soils Using Humic Substances and Microorganisms

Bioremediation of Oil-Polluted Soils Using Humic Substances and Microorganisms

Melanin antibacterial activity of two new strains, SN1 and SN2, of Exophiala phaeomuriformis against five human pathogens

Abstract Melanin is an almost ubiquitous pigment of brown to dark black color synthesized by living organisms. It has excellent potential for application in several fields, especially in pharmaceuticals. Yeasts are known for their ability to synthesize pigments, including melanin. These yeasts are considered black yeasts. However, there is little information on the synthesis of melanin by these yeasts. This work was designed to study the ability of black yeast to produce a diffusible dark pigment on agar. Two strains of black yeast, SN1 and SN2, were isolated from hydrocarbon-polluted soils. Based on morphological, physiological, and molecular analyses, the two strains SN1 and SN2 were identified as new species of the Exophiala phaeomuriformis strain. After pigment extraction, melanin was characterized using UV and Fourier transform infrared spectroscopy. We found that melanin synthesis is strongly affected by light and optimal parameters such as temperature 30°C, salinity between 10 and 30 ppt, and basic pH. Both melanin extracts also showed inhibitory activity against pathogenic germs, and activities were observed on E. coli (33.33 ± 2.88 mm), Pseudomonas aeruginosa (29.33 ± 4.61 mm), and Staphylococcus aureus (24.3 ± 7.65 mm). It was concluded that the melanin of the E. phaeomuriformis strain isolated from oil-polluted soils had high antibacterial activity. This high antibacterial activity could be a suitable source of new antibacterial natural products.

Bioremediation of Engine Oil-Contaminated Soil using Selected Indigenous Moulds

The polycyclic aromatic hydrocarbons (PAHs) utilizing the potential of moulds from engine oil-polluted soils were assessed. These PAHs are known to be toxic, mutagenic and carcinogenic in the environment. Consequently, the study aims to evaluate the potential of indigenous moulds from engine oil in the remediation of contaminated soil. Samples were collected from engine oil-polluted soils from Samonda, Ibadan, Oyo State Nigeria. The ability of four potential indigenous moulds to degrade the PAH fraction of the engine oil-polluted soil sample was assessed using the gas chromatography technique. Four moulds were identified based on their cultural and microscopic characteristics and were confirmed as Aspergillus flavus, Aspergillus parasiticus, Aspergillus oryzae and Aspergillus nidulans. The highest biodegradation potential was observed in treated soil sample containing Aspergillus flavus (55.15%) followed by Aspergillus parasiticus (55.00%), Aspergillus oryzae (44.51%) and the least biodegradation potential was observed in the sample containing Aspergillus nidulans (24.16%) after 60 days of treatment. This study revealed that indigenous mould has the ability to utilize toxic fractions of petroleum products as their sole carbon sources therefore are the major bio-remediating agents in the sampling area.

Modeling the Geotechnical Properties of Small Soil Samples of Oil Polluted Soil: The Power of Supervised Machine Learning Models

ABSTRACT Increasing levels of oil spills in both the terrestrial and aquatic environments destroy aquatic life and crops, fill the air with dangerous fumes, and change the physical and chemical features of the soil. Numerous authors have researched oil spills, but the application of supervised machine-learning models has been incredibly under-explored. Therefore, this study compared four supervised machine learning algorithms (Naïve Bayes Classifier, Decision Tree, Random Forest, and Support Vector Machine) to model the geotechnical properties of oil-polluted soil samples. The soil samples were collected from Engenni Ahoada in Rivers State and Izombe, Imo State, Nigeria. The samples were tested for the following parameters according to the ASTM standard method of measurement: shear strength (SS), liquid limit (LL), plastic limit (PL), bulk density (BD), maximum dry density (MDD), optimum moisture content (OMC), California bearing ratio (CBR), and plasticity index (PI). These measurements and the kind of soil (clay or laterite) constituted the inputs for the machine learning algorithms for predicting pollutant type (crude or diesel). The data from the thirty-two (32) sample size was split into train (70%) and test (30%) sets. The models were trained using the train set, and the test sets were used to validate the models. The support vector machine outperformed the competition, with prediction accuracy in the train and test sets of 96% and 89%, respectively. The findings demonstrated that the plastic and liquid limits are the most crucial factors for determining the pollutants in a sample of polluted soil. Also, plastic limit values less than or equal to 22 are likely contaminated by crude oil, while those above 22 are contaminated by diesel. The results therefore recommend using a support vector machine learning model for predicting the pollutant type of polluted soil samples in the study area.

Remediation of spent engine oil-contaminated soil through biostimulation and bioaugmentation with sodium dodecyl sulphate (SDS) and indigenous hydrocarbonoclastic bacterial isolates.

Pollution caused by spent engine oil has become a major global ecological concern as it constitutes a big threat to plants, animals, microorganisms and the soil ecosystem. This study was undertaken to examine the remediation of spent engine oil-contaminated soil through biostimulation and bioaugmentation with sodium dodecyl sulphate and indigenous hydrocarbonoclastic bacterial isolates. Twelve mesocosms were organized into four groups designated G1, G2, G3 and G4 and each filled with 2.5kg of soil samples. Each group was composed of three mesocosms to produce a triplicate setup. G1 contained pristine soil which served as a positive control. G2 contained a total petroleum hydrocarbon (TPH) of 913.333mg/kg in the untreated oil-polluted soil which served as a negative control. G3 contained a TPH of 913.333mg/kg in the polluted soil inoculated with indigenous hydrocarbonoclastic bacterial isolates. G4 contained a TPH of 913.333mg/kg in the polluted soil mixed with bacterial consortium and sodium dodecyl sulphate. The level of pollution was 36.5% in the triplicate setup G2, G3 and G4. Fourier Transform Infrared spectroscopy was used to determine the degree of hydrocarbon degradation. The initial TPH value of 913.33mg/kg was reduced by 84.44% (142mg/kg) in soil inoculated with indigenous hydrocarbonoclastic bacterial isolates and by 88.28% (106.66mg/kg) in biostimulated soil. Result of this study show that soil stimulation involving bacterial consortium and sodium dodecyl sulphate was more efficient than bioaugmentation strategy alone used in the remediation of spent engine oil-polluted soil.

Surfactin production from Bacillus cereus AHMNAZ1 and its potential applications

BACKGROUND: Biosurfactants are surfactants derived from several types of microorganisms such as bacteria, yeasts and fungi as membrane components or secondary metabolites. OBJECTIVE: To increase BS productivity as a biocompatible, low-toxic substitute for chemical surfactants employed in modern industry and the huge variety of applications they are used in. METHODS: Different media were used in isolation of the biosurfactant BS producers. The most potent bacterial isolate was analysed by 16S-rRNA. Plackett Burman and Box-Behnken Designs were used for optimization conditions. BS was purified by and characterized. RESULTS: Only one strain demonstrated great BS productivity, excellent emulsifying capability (54.5±0.1%) and oil spreading activity which analysed as Bacillus cereus AHMNAZ1 with accession number OP714421.1. The BS was lipopeptide in nature, identified as a surfactin which was stable and has Critical Micelle Concentration of 60 mg/L. Isolated surfactin showed excellent activity against Colon Carcinoma and Breast Carcinoma cell lines and can be used as antimicrobial agent. CONCLUSION: The study found a cheaper way of creating biosurfactants from agro-industrial wastes, delivering a twofold benefit of lowering environmental pollution and manufacturing useful biotechnological products (biosurfactants) with high activity and thermostability. Moreover, it can be used for the bioremediation of oil-polluted soils and in medical fields.