Bioremediation Of Oil-polluted Soil Research Articles

Biosurfactants Production Ability of Lactic Acid Bacteria Strains, Emulsification Activity and Cell Adhesion to Hydrocarbons

The paper presents the results of research carried out for screening of 10 lactic acid bacteria strains with antifungal activity for their ability to produce biosurfactants and to select the most performant strains for further biotechnological application as hydrocarbon-degraders in bioremediation of oil-polluted soils. All the strains of lactic acid bacteria were able to form circle displacement area in engine oil 2T with various diameters, confirming the production of biosurfactants in various amounts. Emulsification activity was registered, with values of emulsification index E24 ranging from minimum 25.75% for the strain LAB 132 to maximum 75.93% for the strain LAB 13. Bacterial cells presented adhesion to hydrocarbons (kerosene), degrees of hydrophobicity variable, ranged between 25,57% for LAB 58 and 75,42% for Lpl and formed emulsions stable for over 7 days. Results of the assay of ionic charge revealed the anionic nature of the biosurfactants. Keywords: biosurfactants, lactic acid bacteria, emulsification, hydrophobicity, cell adhesion to hydrocarbons

Biodegradation of anionic surfactants in the bioremediation of oil-polluted soil

Surfactants are applied as emulsifiers or solubilizers by treatment of polluted soil. Theproblem of secondary pollution has arisen as result of the surfactant-enhanced remediation ofa polluted soil contaminated with hydrophobic organic compounds. Several studies haveshown that the surfactants are biodegradable in aerobic conditions and the biodegradabilitydepended on the chemical properties and concentration of surfactant. A study of the leachingof surfactants from the soil is important, as it is difficult to identify the reason for thereduction of concentration of pollutants in the soil: is it degradation or leaching? Theexperiments were carried out with a fine sandy soil in column tests and CaCO3 was added toincrease soil pH. The soil was treated twice with the bioremediation agent SR-100. The soilpH, the concentrations of anionic surfactant and petroleum hydrocarbons at the differentdepths of soil were determined. The microbial activity of soil fractions was evaluated byrespirometer. The concentration of surfactants was determined colorimetrically as MethyleneBlue active substances (MBAS). The concentration of anionic surfactants decreased in theupper layer of the columns, but it increased in the lower layers. It indicated the leaching ofthe anionic surfactants from soil during experiments of 60 days. The amounts of residualsurfactants were lower in the samples of polluted soil in comparison with unpolluted soil. Thesamples of lower soil fractions had higher microbial activity in comparison with upperfractions. Soil pH was measured as pHH20, pHKcl and pHcac12 instead of the pH of soilsolution, because soil was too dry. The pH of fine sandy soil was 5.8 and during theexperiment the value of pH increased in the lower layer of soil till pHH20 = 7.5.

Microbial Community Structure Shift During Bioremediation of Petroleum Contaminated Soil Using High Throughput Sequencing

The shift in microbial community structure during the bioremediation of oil-polluted soil was analyzed by high-throughput sequencing. The results demonstrated obvious changes in the soil microbial community structure and diversity during bioremediation. The species richness and evenness of the microbial community decreased substantially due to the bioaugmentation treatment. Proteobacteria became the predominant phylum, with a relative increase in abundance from 37.44% to 87.44%. Pseudomonas was the most dominant genus, which increased in abundance from 2.99% to 76.37%. In the biostimulation treated soil, the relative abundance of Proteobacteria decreased from 37.44% to 10.90%, while the phylum Firmicutes increased from 9.16% to 35.32%. At the genus level, the relative abundances of Exiguobacterium and Promicromonospora decreased from 8.49% and 18.96% to 2.19% and 14.97%, respectively. Nocardioides and Bacillus became the dominant genera and increased from 5.56% and 0.29% to 28.95% and 22.70%, respectively. The results indicated that bioaugmentation substantially influenced the soil microbial diversity and community structure. Additionally, the biostimulation treatment maintained the balance in the soil microbial community structure. The stabilization of bacteria community structure is beneficial to petroleum biodegradation in the soil.

Crude oil degradation potential of bacteria isolated from oil-polluted soil and animal wastes in soil amended with animal wastes

The influence of animal wastes on crude oil degradation potential of strains of Proteus vulgaris and Bacillus subtilis isolated from animal wastes (poultry and pig droppings) and petroleum-polluted soil was compared in laboratory studies. Both bacterial strains were selected for high crude oil degradation ability after screening many isolates by the 2,6-dichlorophenol indophenol method. Analyses by gas chromatography (GC) showed that degradation of crude oil was markedly enhanced (88.3–97.3% vs 72.1–78.8%) in soil amended with animal wastes as indicated by the reduction of total petroleum hydrocarbon (TPH). TPH reduction by animal waste bacterial strains in animal waste-amended soil was more than the reduction by strains from soil contaminated with petroleum (P < 0.001). The greatest reduction of TPH (96.6–97.3% vs 80.4–95.9%) was by poultry waste strains and it occurred in soil amended with poultry waste. GC analyses of n-alkanes showed that although shorter chains were preferentially degraded [32.0–78.5% (C8–23) vs 6.3–18.5% (C24–36)] in normal soil, biodegradation of longer chains increased to 38.4–46.3% in animal waste-amended soil inoculated with the same animal wastes’ strains. The results indicate that these animal waste strains may be of potential application for bioremediation of oil-polluted soil in the presence of the wastes from where they were isolated.

Effect of biostimulation, temperature and salinity on respiration activities and bacterial community composition in an oil polluted desert soil

Bioremediation of oil-polluted soils under the extreme environmental conditions of deserts is challenging. Lack of nutrients, elevated temperatures and high salinities, caused by continuous evaporation of irrigation water/seawater, are among the major environmental factors that influence the diversity and activity of soil microorganisms. We compared, using microcosms, the effect of different temperatures and salinities on respiration activities, oil mineralization and bacterial community composition in desert soils with and without the addition of inorganic nutrients and exogenous bacteria. The addition of nutrients resulted in ca. 20% increase in oil mineralization rates, however additional exogenous bacteria lead to a further increase of only 1%. While the evolved CO2 increased with increasing temperatures, it decreased with increasing salinity in both untreated and biostimulated soils. The maximum amount of evolved CO2 reached 18.4 ± 1.1 mg-CO2 g−1 in the biostimulated soil at 50 °C and this corresponded to ca. 10% oil mineralization. Bacterial communities exhibited shifts at different temperatures and salinities in the favor of genera that contain potential oil-degrading aerobic and anaerobic bacteria. We conclude that fluctuations in temperature and salinity of desert soils will directly influence the activity and diversity of microorganisms therein and consequently affect the efficiency of applied bioremediation treatments.

Bioremediation of oil-polluted soils: Using the [13C]/[12C] ratio to characterize microbial products of oil hydrocarbon biodegradation

Bioremediation of oil-polluted soils: Using the [13C]/[12C] ratio to characterize microbial products of oil hydrocarbon biodegradation

Bioremediation of oil-polluted soils: using the [13C]/[12C] ratio to characterize microbial products of oil hydrocarbon biodegradation

We compared data on the extent of bioremediation in soils polluted with oil. The data were obtained using conventional methods of hydrocarbon determination: extraction gas chromatography-mass spectrometry, extraction IR spectroscopy, and extraction gravimetry. Due to differences in the relative abundances of the stable carbon isotopes (13C/12C) in oil and in soil organic matter, these ratios could be used as natural isotopic labels of either substance. Extraction gravimetry in combination with characteristics of the carbon isotope composition of organic products in the soil before and after bioremediation was shown to be the most informative approach to an evaluation of soil bioremediation. At present, it is the only method enabling quantification of the total petroleum hydrocarbons in oil-polluted soil, as well as of the amounts of hydrocarbons remaining after bioremediation and those microbially transformed into organic products and biomass.

The Evaluation of Process of Bioremediation of Oil-Polluted Soils by Different Strains of Pseudomonas

The determination of content hydrocarbon of diesel fuels and individual hydrocarbons in oil-polluted soil before and after bioremediation by oil-oxidational microorganisms was carried out by method of chromato-mass-spectrometry. It has been shown that changes in composition hydrocarbons of diesel fuels and individual hydrocarbons in soil observe during growth of microorganisms on this soil.

Efficiencies of introduction of an oil-oxidizing Dietzia maris strain and stimulation of natural microbial communities in remediation of polluted soil

Two approaches to bioremediation of oil-polluted soils are compared: use of active degrader strain Dietzia maris AM3 and stimulation of natural microflora. Introduction of D. maris AM3 to soil freshly polluted with oil accelerated its remediation twofold within the first month in comparison with the stimulation. After three months, the purification degrees were approximately equal. By the end of bioremediation, the soil with the introduced strain had higher dehydrogenase and catalase activities. In soil with aged pollution, introduced strain D. maris AM3 did not affect the rate of oil product degradation, and no significant differences between the two bioremediation methods were detected in purification degree and biological activity of soil after three months.

Bioremediation of oil-polluted soil by Lentinus subnudus , a Nigerian white-rot fungus

Inspite of the realization and studies on the use of microorganisms in degrading hydrocarbons there has been very little work on indigenous white-rot fungi in Nigeria, a leading oil – producing country. the ability of Lentinus subnudus to mineralize soil contaminated with various concentrations of crude oil was tested. Organic matter and carbon were higher than the control at all concentrations of crude oil contamination in soils inoculated with L. subnudus for 3 months. Nutrient contents were generally higher after 6 months of incubations except potassium levels which were not significantly different from the control. As for the total petroleum hydrocarbon (tph) in crude – oil contaminated soils; the highest rate of biodegradation was at 20% concentration after 3 months and 40% after 6 months of incubation. Key words : bioremediation, crude oil, total petroleum hydrocarbon oil-polluted soil, Lentinus subnudus African Journal of Biotechnology Vol. 4 (8), pp. 796-798

Bioremediation of oil-polluted soil by Lentinus subnudus, a Nigerian white-rot fungus

Inspite of the realization and studies on the use of microorganisms in degrading hydrocarbons there has been very little work on indigenous white-rot fungi inNigeria, a leading oil – producing country. the ability of Lentinus subnudus to mineralize soil contaminated with various concentrations of crude oil was tested. Organic matter and carbon were higher than the control at all concentrations of crude oil contamination in soils inoculated with L. subnudus for 3 months. Nutrient contents were generally higher after 6 months of incubations except potassium levels which were not significantly different from the control. AS for the total petroleum hydrocarbon (tph) in crude – oil contaminated soils; the highest rate of biodegradation was at 20% concentration after 3 months and 40% after 6 months of incubation. Key words: Bioremediation, crude oil, total petroleum hydrocarbon oil-polluted soil,Lentinus subnudus.

Purification of Soil from Oil Pollutants with the Use of Denitrifying Hydrocarbon-Oxidizing Microorganisms

The efficiency of an oil-oxidizing microbial community in the bioremediation of oil-polluted soil was studied under laboratory conditions. A specific feature of the community was its ability to oxidize oil hydrocarbons under both aerobic and anoxic conditions. The degree of oil-hydrocarbon degradation in various bioremediation modes increased as follows: self-remediation (40%) < nitrate application (42%) < introduction of the denitrifying oil-oxidizing community (50%) < introduction of the denitrifying oil-oxidizing community plus nitrate application (60%). The intensification of bioremediation is related to the increase in the population of the hydrocarbon-oxidizing microorganisms, first of all, denitrifying ones, resulting from the introduction of the community.

Biodegradation of black oil by microflora of the Bay of Biscay and biopreparations

Recent research has shown that the bioremediation of oil-polluted soil by activation of microflora is not always advantageous when compared with the introduction of oil degrading microorganisms. Although microflora isolated from oil-polluted sites is adapted for growth under the above conditions, this does not imply a high rate of oil degradation. Indeed, it has been shown that the hydrocarbon-oxidative activity of isolated strains to black oil was 13.1–17.3% (incubation for 10 days at 24 °C), while the activity of a mixture of three aboriginal strains was 17.8%. At the same time, the hydrocarbon-oxidative activity of associations of the strains isolated from other regions was 24.0–30.0% (in 10 days).