Oil-contaminated Soil Samples Research Articles

Polycyclic Aromatic Hydrocarbon (PAHs) Levels in Treated Spent Engine Oil Contaminated Soil from Automechanic Workshop Site in Wukari, Nigeria

Spent engine oil contaminated soil samples were collected and divided into three portions along with uncontaminated soil sample collected 10 meters away from the contaminated site. Two of the contaminated soil samples were treated with 0.5M NaOH and heat at 2500C respectively. All the samples were extracted with appropriate solvents using sonication, cleaned up and then analyzed with gas chromatograph coupled to flame ionization detector. The results show that total PAHs concentration of contaminated soil sample was 333.6820 mg/kg, contaminated soil sample treated with 0.5M NaOH, 104.8540 mg/kg, contaminated soil sample treated with heat at 2500C was 180.0905 mg/kg and the uncontaminated soil sample, 0.7084 mg/kg. The results showed that Wukari mechanic village is contaminated with PAHs through indiscriminate disposal of spent engine oil. Furthermore, treatment with 0.5M NaOH was a more effective means of remediation relative to treatment with heat at 250oC for two hours. The study will be an appropriate guide for the artisans following enlightenment about the possible threat that contact with PAH contaminated soils could have on their health.

Biotechnological Potential of Oil-Tolerant Strains for Possible Use in Bioremediation

The release of oil into the environment represents a pervasive problem stemming from oil exploration, accidents, transportation and releases from landfills, storage facilities or industrial plants. Compared to conventional and costly techniques, bioremediation is an attractive and promising alternative, as it can selectively degrade pollution without affecting the natural features of the site and the flora and fauna living there. In this study, the isolation, identification and characterization of autochthonous bacterial strains from a crude oil-contaminated soil sample was carried out under batch conditions over a period of 28 days. The initial colony forming units value for bacteria was 1.15 × 109/g of soil. The results show that the activity of bacteria was highest at a pH of 7.25. Based on morphology, biochemical tests and an analysis of MALDI TOF, isolated autochthonous bacterial species were identified as Bacillus megaterium, Bacillus licheniformis, Bacillus cereus and Pseudomonas chlororaphis. Since allochthonous bacteria are not highly efficient in a new environment due to their low adaptability and competition with indigenous microorganisms, these autochthonous microorganisms play a pivotal role in enhancing the bioremediation process on an applicable, industrial scale. This advancement aligns with the principles of sustainable development and the green economy, as purified soil is suitable for rational reuse in the environment.

Evaluation of Organic Treatments for Enhanced Bioremediation of Crude Oil Impacted Soil in Bayelsa State, Nigeria

The aim of this study was to evaluate organic treatments for enhanced bioremediation of crude oil impacted soil in Bayelsa State, Nigeria. Koroama community in Gbarain clan, Yenagoa local government area, Bayelsa State, Nigeria was randomly selected for the study. The experimental research design was adopted for this study, which was carried out for 28 days. The required soil samples were collected at a depth of 0 – 15cm from a 3 x 3m experimental plot developed in a farmland in Koroama community. Five sampled points, in the form of flat beds A, B, C, D and E respectively were randomly selected. Sampled beds A to D were simulated (contaminated) with 2.25kg of crude oil. The objective is to simulate conditions of a major crude oil spill. The crude oil contaminated soil samples were then allowed to condition for 6 days before treatment with 2kg organic treatments like goat manure (GM), poultry droppings (PD) and the combination of goat manure and poultry droppings (GM & PD). Bed E was unpolluted and untreated (control A) while Bed D was crude oil impacted and untreated soil (control B). The study showed that the impact of crude oil on the soil affects both the physical properties of the soil. The study also showed that the sampled organic treatments were all effective in restoring the physical properties of the crude oil impacted soil. At the end of the study, GM showed the highest TPH degradation rate (62.1%) followed by PD (57.1%) and the least, the combination of GM & PD (52.0%). Hence, the application of GM, PD and the combination of GM & PD are highly recommended for bioremediation of crude of impacted soil with special preference to GM.

Effects of natural and prolonged crude oil pollution on soil enzyme activities

In this study the effects of natural and long-term oil pollution levels (H: high, M: moderate and L: low) on the activity of lipase, β-glucosidase, urease, phosphatase, and dehydrogenase were analyzed. For this purpose, 120 oil-contaminated soil samples were collected from four locations located in oil-rich region of the west of Iran (Kermanshah province, Iran). After determining the physicochemical characteristics of soils, microbial counting and enzyme activities were measured. To determine the total bacterial population and bacteria involved in crude oil decomposition, bacterial counting was done in NA and CFMM culture media, respectively, which had a direct relationship with the increase in crude oil content. The average percentage of crude oil measured by Soxhlet method was 4.03%, 9.95% and 22.50% respectively for L, M and H levels. The results showed that the bacterial population increased with the increase of the contamination intensity. All the studied enzymes, except urease, had the highest activity in heavily polluted soils (H soil), and their lowest activity was observed in lightly polluted soils (L soils). Location 1 had the highest bacterial population as well as the highest activity of dehydrogenase (52.13 μg TPFg−1 h−1), acid phosphatase (35.86 μg PNPg−1 h−1), alkaline phosphatase (78.13 μg PNPg−1 h−1), lipase (92.58 μ MLA g−1 h−1) and β-glucosidase (21.67 μg PNPg−1 h−1) enzymes. In the soil samples of location 4, which had the lowest number of bacteria, the highest activity of urease enzyme (592.36 μg NH4g−1 h−1) was obtained. Principal components analysis (PCA) was also performed and 67% of the cumulative of the samples could be explained by the first two components (biochemical and physical). The findings of this research showed that natural and prolonged crude oil pollution caused the selection of oil-resistant microbial communities, and therefore we saw their positive response to the presence of oil compounds and increased enzyme activity other than urease activity.

Kinetics of bioremediation of crude oil polluted soil using potato peels as bio-stimulant

This study investigated the utilization of bio-stimulant derived from agro-based resource (potato peels) in the remediation of crude-oil contaminated soil. At a constant proportion of crude oil contamination, varying concentration of the biostimulant (5ml, 10ml, 15ml and 20ml) were introduced for the treatment (bioremediation and degradation) of the contaminated sites and left for a degradation period in plastic vessels. Periodic sampling of soil from each vessel was carried out at 5 days interval for total petroleum hydrocarbon analysis. Results indicated that after 20 days of exposure to the organic biostimulants, biodegradation of crude oil contaminated soil samples was directly proportional to the potato peels dosage. The potato peels (PO) derived biostimulant recorded 94.43 percentage degradation at 20ml dosage and 20 days contact time. Oil contaminated soil samples amended potato peels biostimulant recorded half-life of 0.702day and biodegradation rate constants of 0.986day-1. The zero order kinetic model best described the bioremediation kinetic behaviour of the bioremediation process. The findings of this research suggest that potato peels can be used as an effective organic amendment for the biodegradation of crude oil contaminated soil.

Extraction of biosurfactant from pseudomonas aeruginosa inhabiting oil-spilled soils

BackgroundScreening for biosurfactant-producing microbes involves the process of sampling and isolating bacteria from various environmental sources. Hydrocarbon-contaminated locations are considered ideal sources for isolating bacteria that produce biosurfactants. This is because these microbes have adapted to living in oil-contaminated environments and have developed mechanisms to produce biosurfactants as a means of survival. Therefore, screening microbes from such locations increases the likelihood of finding bacteria capable of producing biosurfactants.ResultsThis investigation aimed to isolate bisurfactant-producing bacteria from oil-contaminated soil samples, with a particular focus on Pseudomonas aeruginosa. Out of the 10 samples collected, four were confirmed to be P. aeruginosa, and all strains showed positive results for antagonistic, hemolytic, and emulsification tests. The strains were effective against B. subtilis, S. aureus, and E. coli but less effective against A. hydrophila. The PS10 strain exhibited the highest emulsification index, while PS08 showed the lowest. Based on microscopic and biochemical examination, P. aeruginosa was identified as the most effective isolate.ConclusionThese findings highlight the potential of P. aeruginosa as a biosurfactant producer for industrial and environmental applications. However, further studies are needed to fully understand the biosurfactant production potential of these strains and to optimize the conditions for biosurfactant production.

Physicochemical and microbial alterations in crude oil-contaminated soil samples

Environmental pollution is becoming an issue of concern due to its negative impact on the living and non-living components of the environment. Crude oil and its products are the major sources of environmental pollution that renders negative impact on the soil mineral components and microorganism. This study was thus carried out to determine the effect of crude oil on soil physicochemical properties, bacterial and fungal population. The experiment lasted for 42 days and the analysis were carried out at days 0, 14, 28 and 42 using standard protocols. Results obtained show significant changes (P ≤ 0.05) in hydrocarbons and other physicochemical parameters such as pH, nitrate, electrical conductivity, sodium ion, calcium ion, phosphate and magnesium ion, when the control was compared with crude oil contaminated soil. Also, soil bacterial and fungal count decreased significantly (P ≤ 0.05) with increasing concentrations of crude oil indicating its toxicity to soil microbial consortium. However, results also showed that hydrocarbon-degrading microorganisms strived at higher concentrations but insignificantly (P ≤ 0.05) in comparison with the control. Owing to the result obtained in this study, crude oil exploration should be properly managed to prevent spillages that negatively impact on the environment.

Statistical Optimization of Biosurfactant Production from Aspergillus niger SA1 Fermentation Process and Mathematical Modeling.

In this study, we sought to investigate the production and optimization of biosurfactants by soil fungi isolated from petroleum oil-contaminated soil in Saudi Arabia. Forty-four fungal isolates were isolated from ten petroleum oil-contaminated soil samples. All isolates were identified using the internal transcribed spacer (ITS) region, and biosurfactant screening showed that thirty-nine of the isolates were positive. Aspergillus niger SA1 was the highest biosurfactant producer, demonstrating surface tension, drop collapsing, oil displacement, and an emulsification index (E24) of 35.8 mN/m, 0.55 cm, 6.7 cm, and 70%, respectively. This isolate was therefore selected for biosurfactant optimization using the Fit Group model. The biosurfactant yield was increased 1.22 times higher than in the nonoptimized medium (8.02 g/l) under conditions of pH 6, temperature 35°C, waste frying oil (5.5 g), agitation rate of 200 rpm, and an incubation period of 7 days. Model significance and fitness analysis had an RMSE score of 0.852 and a p-value of 0.0016. The biosurfactant activities were surface tension (35.8 mN/m), drop collapsing (0.7 cm), oil displacement (4.5 cm), and E24 (65.0%). The time course of biosurfactant production was a growth-associated phase. The main outputs of the mathematical model for biomass yield were Yx/s (1.18), and μmax (0.0306) for biosurfactant yield was Yp/s (1.87) and Yp/x (2.51); for waste frying oil consumption the So was 55 g/l, and Ke was 2.56. To verify the model's accuracy, percentage errors between biomass and biosurfactant yields were determined by experimental work and calculated using model equations. The average error of biomass yield was 2.68%, and the average error percentage of biosurfactant yield was 3.39%.

Assessment of natural radiation in contaminated automobile workshop soils

The presented study aims to identify and quantify the natural radionuclides activity concentrations on the top and sub-soils around mechanic workshops in Ojo and Ijegun, Lagos, Nigeria. Based on these measured radionuclides activity concentrations, radiological hazard indices are assessed. Twenty oil-contaminated soil samples were collected, and the levels of natural radionuclides activity are measured by applying gamma spectrometry The measured radionuclides with authoritative regularity are linked with the natural decay series of 238U (226Ra) and 232Th as well as the series of non-decay 40K. The obtained results show that the mean radionuclides activity concentrations in the collected oil-contaminated soils samples are 14 ± 4 Bq kg−1, 105 ± 55 Bq kg−1, and 90 ± 33 Bq kg−1, for 226Ra, 232Th, and 40K respectively. It was founded that the 226Ra radionuclide is the lower present in the oil-contaminated soils samples. The radiological assessments were evaluated in terms internal hazard index (0.54), and external hazard index (0.55) both of which are below the UNSCEAR-2000 standard limit. Consequently, the radiological assessment indicated that long-time exposure to those radionuclide's strength confuses integral hazards.

Heavy metals in crude oil-polluted soil and the remediation potentials of heat-stable biocatalytic remediation cocktail (HBRC) and its residue

This study investigated heavy metals in crude oil-polluted soil and the remediation potentials of Heat-Stable Biocatalytic Remediation Cocktail (HBRC) called Garbage Enzyme and its residue (HBRCR). The Crude oil-contaminated soil sample was collected from Agbura Community, Yenagoa, Bayelsa State. HBRC was produced from three substances; water, fruit skin (orange, pineapple, watermelon, plantain and banana peels) and brown sugar in a ratio of 10: 3: 1 respectively. They were subjected to fermentation for 90 days. The soil sample was divided in to ten groups. Group 1 served as the control, Group 2 untreated while Groups 3 to 10 were given different treatments for 180 days. Heavy metals (Hg, Cr, Cd, Pb and Ni) concentrations were analyzed using an Atomic Absorption Spectrophotometer (AAS). Significant decreases at p≤0.05 of Hg, Cr, Cd, Pb and Ni were observed in groups 3 to 10 when compared to groups 1 and 2. Results obtained from the study revealed that there was a decrease in concentrations of various heavy metals. Hg concentrations in Groups 1 to 10 were reduced by 0.00%, 9.97%, 76.36%, 63.61%, 65.61%, 60.93%, 83.17%, 69.50%, 68.41% and 79.35% respectively. Similarly, Cr concentrations in Groups 1 to 10 were reduced by 19.73%, 11.78%, 96.05%, 36.17%, 51.79%, 74.45%, 92.09%, 55.07%, 85.12% and 80.70% respectively. Also, Cd concentrations in Groups 1 to 10 were reduced by 40.00%, 26.67%, 100.00%, 98.02%, 100.00%, 86.36%, 100.00%, 100.00%, 100.00% and 100.00% respectively. In like manner, Ni concentrations in Groups 1 to 10 were reduced by 18.52%, 33.68%, 45.48%, 69.55%, 47.11%, 44.05%, 51.05%, 64.57%, 65.49% and 65.41% respectively while Pb concentrations in Groups 1 to 10 were reduced by 8.09%, 3.32%, 48.05%, 55.74%, 60.77%, 55.32%, 100.00%, 41.25%, 100.00% and 63.54% respectively. The Results from this study showed that HBRC and HBRCR elicited significant removal of heavy metals from crude oil-contaminated soil and they could be used as remediation agents for heavy metals.

Molecular identification and characterization of indigenous bacterial strains isolated from soils around some oil refineries in Iran

One of the main causes of soil pollution is the release of crude oil into the environment. Indigenous microorganisms with the capability of biodegrading hydrocarbon components can be used to improve the efficiency of microbial bioremediation technology. Here, oil-contaminated soils were collected from five oil refineries (Abadan, Isfahan, Tehran, Tabriz and Shiraz) for screening and isolation of geographically adaptive indigenous oil-degrading bacteria. Bacterial colonies from oil-contaminated soil samples were isolated, which were able to grow in a medium containing crude oil, light, and heavy diesel, as a sole carbon source. Twelve strains were isolated, purified, and identified, using the 16S rRNA gene sequencing analysis. The isolates belonged to five species, including Achromobacter spanius, Klebsiella quasipneumoniae, Ochrobactrum intermedium, Citrobacter amalonaticus, Pseudomonas aeruginosa. These bacterial strains were capable of growing in media containing crude oil, light and heavy diesel for 7 to 9 days and had the potential for biosurfactant production. These bacterial strains can be considered as geographically adaptive bacteria, creating preliminary data for further research to utilize their bioremediation potential.

Identification of hydrocarbon-degrading bacterial consortium isolated from the oil-contaminated muddy soil in Hanoi, Vietnam

Bioremediation is a promising approach for treating oil-contaminated environments. The main objective of this study was to isolate bacteria capable of degrading hydrocarbons for application in oily wastewater treatment from oil-contaminated sites in Hanoi, Vietnam. The bacterial consortium studied was obtained from an oil-contaminated muddy soil sample enriched with crude oil mixed with diesel oil as a carbon source. The reconstituted consortium was able to degrade 93% of the oil content after 7 days of testing. A total of five pure bacterial strains were isolated on TSA agar from the complex microbial communities and were selected as potential candidates for oily sludge biodegradation processes. These isolates were identified based on their morphological and biochemical characteristics. By using molecular biology techniques, five hydrocarbons degrading bacteria were investigated and identified as Pseudomonas mendocina strain MD1 (OL687411.1), Pseudomonas hydrolytica strain MD2 (OL771695.1), Brucella intermedia strain MD3 (OL687412.1), Pseudomonas stutzeri strain MD4 (OL687413.1), and Stenotrophomonas nitritireducens strain MD5 (OL687414.1). The morphological and biochemical characterization of these bacteria showed that five of them were Gram-negative, rod-shaped, catalase positive, the ideal pH was neutral, and the optimum growth temperature was 30ºC in a culture medium with a salinity of 0.5%. These strains are capable of producing extracellular enzymes, such as lipase, amylase, cellulase, and protease.

Evaluation Of Biodegradation Ability Of Bacterial Consortium In Comparison With Combination Of It With Plant Species For Their Phytoremediation Potential

Oil and its derivatives spills have been a major issue across decades due to transport, import, Export and accidents with its wider use in industry and it is difficult to be biodegraded. Many techniques were developed to clean up petroleum contaminated soil, among all of them, the biological treatments are more efficient and economic compared to chemical and physical ones. Bioremediation is applied as a treatment technology that is cost-effective, ecologically friendly and efficient for the decontamination of hydrocarbon pollution. In this study, crude oil contaminated soil samples were collected from oil extraction fields in Libya. The bacterial strains were isolated using selective media (agar containing crude oil). Isolated bacteria were identified using microbial features and selective media and then used in biodegradation experiment of 0.5% and 1% of crude oil contaminated soil. The bacterial concentration was adjusted to 1.5 x 108 scf/ml before supplementing in the soil. Three plants were chosen to perform experiment (Malva punilora, Ricinus communis and Triticum repens) on 0.5% and 1% crude oil contaminated soil. The chosen species were implanted directly in the contaminated soil together with prepared bacterial consortia. Soil sample (triplicate) was taken from each experiment at zero time, after 15 days, and 30 days of experiment, hexane was added to the soil samples and the absorbance was measured using spectrophotometer at 360 nm. As a result, two bacterial strains proved to be oil biodegrades were isolated and identified as Escherichia coli and other bacillus bacteria. The percentage of crude oil removal by bacteria was more than 60% in the soil contaminated by 0.5% of crude oil after 15 and 30 days of experiment, while it was 30% at 1% crude oil contaminated soil after 15 days and increased to be 75% after 30 days of experiment. The experiment included combination between plants and bacteria resulted in the 90% of removal by Triticum repens and bacterial mixture at 0.5 crude oil after 30 days, and 80% of removal for 1% contaminated soil using the same plant. In general, both techniques were effective in crude oil removal. Triticum repens showed good results in crude oil removal. This suggests more field application of this plant on crude oil contaminated oil

Isolation, Molecular Identification and Amino Acid Profiling of Single-Cell-Protein-Producing Phototrophic Bacteria Isolated from Oil-Contaminated Soil Samples.

In the current study, soil samples were gathered from different places where petrol and diesel filling stations were located for isolation of photosynthetic bacteria under anaerobic conditions using the paraffin wax-overlay pour plate method with Biebl and Pfennig’s medium. The three isolated strains were named Rhodopseudomonas palustris SMR 001 (Mallapur), Rhodopseudomonas palustris NR MPPR (Nacahram) and Rhodopseudomonas faecalis N Raju MPPR (Karolbagh). The morphologies of the bacteria were examined with a scanning electron microscope (SEM). The phylogenetic relationship between R. palustris strains was examined by means of 16S rRNA gene sequence analysis using NCBI-BLAST search and a phylogenetic tree. The sequenced data for R. palustris were deposited with the National Centre for Biotechnology Research (NCBI). The total amino acids produced by the isolated bacteria were determined by HPLC. A total of 14 amino acids and their derivatives were produced by the R. palustris SMR 001 strain. Among these, carnosine was found in the highest concentration (8553.2 ng/mL), followed by isoleucine (1818.044 ng/mL) and anserine (109.5 ng/mL), while R. palustris NR MPPR was found to produce 12 amino acids. Thirteen amino acids and their derivatives were found to be produced from R. faecalis N Raju MPPR, for which the concentration of carnosine (21601.056 ng/mL) was found to be the highest, followed by isoleucine (2032.6 ng/mL) and anserine (227.4 ng/mL). These microbes can be explored for the scaling up of the process, along with biohydrogen and single cell protein production.

Promoting Resuscitation of the VBNC Bacteria and Enrichment of Naphthalene-degrading Bacteria from Oil-contaminated Soils with the Rpf4 from Rhodococcus erythropolis KB1

Nowadays, more than 90% of bacteria in nature are in a viable but not culturable (VBNC) state, and they cannot be separated by traditional plate culture methods. However, resuscitation-promoting factors (Rpf) participate in recovery of dormant cells and promoting bacterial growth. The Rpf4 of Rhodococcus erythropolis KB1 is a Rpf like protein of Micrococcus luteus and contained the Rpf domain and LysM domain. In this study, an expression vector for the rpf4 gene was constructed and expressed in Escherichia coli. The recombinant protein Rpf4 was purified by Ni2+-affinity chromatography. The recombinant protein showed a muralytic activity of 549 ± 28.77 U/mg. The purified Rpf4 could increase R. erythropolis KB1 cell proliferation and improve the resuscitation of R. erythropolis cells that were VBNC. The Rpf4 altered the diversity of naphthalene-degrading bacteria enriched from oil-contaminated soils. Based on the high-throughput sequencing, we found that Proteobacteria and Actinobacteria phyla increased from 76.10% and 0.029% to 98.23% and 0.401% after the Rpf4 treatment, while the Bacteroidetes phylum decreased from 22.70% to 0.76%. The genera Enterobacter, Citrobacter, and Acinetobacter increased from 0.0054%, 0.001%, and 0.745% to 19.02%, 6.34% and 2.49%. Some new genera such as Bifidobacterium, Limnobacter, Alloprevotella, Hydrogenophaga, and Nevskia were founded in the treatment group. Meanwhile, 23 naphthalene-degrading bacteria were isolated by adding the Rpf4 protein to the oil-contaminated soil samples. Study on the naphthalene-degrading bacteria will provide a basis for the microbial degradation of naphthalene and other polycyclic aromatic hydrocarbons and discover the wider application value of Rpf.

SORPTION OF OIL BY MECHANOCHEMICALY ACTIVATED SHUNGITE

In the paper the sorption capacity of shungite rocks of the Koksu field (Kazakhstan) in relation to the oil from the Karazhanbas and Tengiz fields (Kazakhstan) were studied. Oil spills occurring during production, gathering, transportation, storage and refining, and repair work on wells are an urgent environmental problem. There are effective methods of soil purification, including particular interests addressed to sorption process. The aim of this research is to study oil sorption by shungite rocks of the Koksu deposit after mechanochemical activation. The mechanochemical activation of shungite rock samples was carried out in a planetary ball mill at different speeds of rotation and ratios of ball mass to the sample. The developed sorbents based on shungite rocks of the Koksu deposit were tested for cleaning samples of oil-contaminated soils and their sorption capacities under dynamic and static conditions were determined. For the sorption of oil, the sorbent based on shungite of shale grade (TS) after mechanochemical activation is recommended, which sorption capacity under dynamic conditions is 2.57-2.85 g/g. Sorption of oil from 10 % of oil contaminated soil samples with the sorbents based on shungite after mechanochemical activation showed sorption capacity of 0.44-0.45 g/g in 60 days under static conditions. The practical significance of the research lies in the prospects of using shungite rocks to clean up oil spills.

A Study on Isolation and Identification of Exopolysaccharide (EPS) producing Bacteria from Soil

Abstract: Polysaccharides are important potent molecules with their structural and compositional complexity which led to wide range of applications in various industries. The exopolysaccharides of microbial origin are released in response to extreme environmental conditions for the purpose of survival. The present study focuses on the isolation of exopolysaccharide producing bacteria from the soil sample and oil contaminated soil sample. Screening for the EPS production by the isolates is determined by the dry weight determination of precipitates of EPS and quantitative estimation of glucose content of EPS by PhenolSulphuric acid method. In the present study, out of 5 bacterial isolates isolated on screening, Lactobacillus sps and Pseudomonas sps. isolates produced the precipitates of EPS whose dry weight was determined to be 0.09g and 0.17g respectively. Further, glucose concentration of EPS was quantitatively determined. The glucose content of Lactobacillus sps. isolate was 0.1125mg/ml and Pseudomonas sps. isolate is 0.2875mg/ml. The EPS producing isolates were further grown in the presence of carbon sources like Glucose, Lactose, Maltose and Sucrose to determine the best utilizable carbon for their growth. The most utilizable carbon source for maximum growth of EPS producing isolates was determined to be sucrose with 2% concentration. All the 5 bacterial isolates were screened for their ability of antibiotic resistance. The EPS producing isolates, Lactobacillus sps, Pseudomonas sps were found to be resistant towards all the antimicrobial agents owing to the presence of EPS protective layer around their cell wall than non-EPS producing isolates. Keywords: Exopolysaccharide, Screening, Carbon sources, Antibiotic resistance.

Effect of nutritional factors and growth conditions on biosurfactant production by Pseudomonas mendocina andPseudomonas oleovorans isolated from oil contaminated soil in Jeddah city

Objectives: The current study aimed to investigate the impact of different nutritional factors and growth conditions on biosurfactant production by bacterial isolates (EMB16 and EMB21) isolated from oil-contaminated soil samples. Methods: Based on the used quantitative and qualitative screening method in current study, the selected bacterial isolates showed a high potential to produce biosurfactant. Results: By using 16S rRNA sequence analysis, the bacterial isolates EMB16 and EMB21 were found to be closely related to Pseudomonas mendocina and Pseudomonas oleovorans, respectively. The ultimate yields of biosurfactant (8.06±0.06 mg/ml) by Ps. mendocina EMB16 was with corn oil as a carbon source, urea as a nitrogen source, C/N ratio of 30, pH value of 7, and 2% inoculum size. For Ps. oleovorans EMB21, the maximum biosurfactant production (4.68±0.14mg/ml) was achieved by diesel oil as a carbon source, urea as a nitrogen source, C/N ratio of 30, pH of 7, and 5% size of inoculum. The best incubation period and temperature for the examined strains was 168 hrs. at 37℃. Conclusion: The results proved that Ps. mendocina EMB16 was the most efficient biosurfactant producer as it showed the greatest amount of biosurfactant concentration and lowestvalue of surface tension measurement with an emulsification index of 67±6%.

Isolation, screening and molecular characterization of biosurfactant producing bacteria from soil samples of auto repair shops.

A total of 107 bacterial strains were isolated from used motor oil contaminated soil samples from auto-repair shops. The isolates were evaluated for their biosurfactant production abilities by employing a series of screening techniques, including hemolytic assay, oil displacement assay, drop-collapse assay, and parafilm M test. The potential biosurfactant producers were characterized by 16S rDNA-based molecular tools and were identified as Proteus mirabilis, Klebsiella pneumoniae, Enterobacter cloacae, Micrococcus sp., Citrobacter sp., and Bacillus sp. The widest clearing zone with a diameter of 6.5cm was observed upon the addition of cell-free supernatant (CFS) from P. mirabilis SLM-B52 as assayed by the oil displacement test. Remarkable emulsification indexes, equivalent to 42% (against kerosene), 53% (against xylenes), and 50% (against benzene and toluene), were recorded by the CFSs of Micrococcus sp. SLM-B28, P. mirabilis SLM-B85, and K. pneumoniae SLM-B46, respectively. Du Noüy tensiometer analysis showed that biosurfactant produced by P. mirabilis SLM-B52 has the highest surface tension reduction capacity with a value of 30.5 mNm-1. The emulsifying activity of a CFS from P. mirabilis was also described in this study for the first time. Taking together, biosurfactants from promising bacterial strains have potential application in microorganism-based biodegradation processes of hydrocarbons which cause detrimental effects on the environment.

Gravimetric Profile of Hydrocarbon Degrading Bacterial and Fungal Isolates from Contaminated Soil Samples in Ado-Ekiti, Nigeria

One of the biological compounds limiting soil water retention capacity is oil when present due to its hydro-nature. However, some microorganisms exhibit the capacity to degrade oil as a source of carbon, whereby the soil quality is retained and enhanced. Hence, the gravimetric profile of hydrocarbon degrading bacteria and fungi isolated from oil contaminated soil samples was investigated. Soil samples were collected from surface and 10m depth from six different mechanic workshops and generator sites. The pour plate technique was used to isolate the microorganisms. All pure isolates were sub-cultured using Bushnell Haas agar and the isolated bacteria were identified by their morphological and biochemical characteristics. The soil samples pH range was 4.3 - 6.4. Bacteria isolated included Pseudomonas spp., Staphylococcus spp., Microccocus spp., Acinetobacter spp., and Bacillus spp. The fungi isolated included Aspergillus spp., Rhizopus spp., Candida spp., Trichoderma spp. and Penicillium spp. Degradation of kerosene, diesel, crude oil, engine oil, and spent engine oil was allowed using Acinetobacter baumanni, P. aeruginosa, B. subtilis, and S. aureus. Gravimetric analyses were used to determine the percentage of petroleum hydrocarbon degraded by bacterial isolates. The highest percentage of degradation was between P. aeruginosa and B. subtilis. Pseudomonas aeruginosa degraded 97.4% diesel, 88.2% kerosene, 71.3% crude oil, 80.7% engine oil and 78.2% spent engine oil; while Bacillus subtilis degraded 71% diesel, 97% kerosene, 89.6% crude oil, 87% engine oil and 72.6% spent engine oil. This study revealed that bacterial and fungal isolates from oil contaminated soils exhibited the potentials to degrade oil and bioremediation using these microorganisms was possible.