Biodegradation of crude oil by soil microorganisms in the tropic

Five microorganisms, three bacteria and two yeasts, capable of degrading Tapis light crude oil were isolated from oil-contaminated soil in Bangkok, Thailand. Soil enrichment culture was done by inoculating the soil in mineral salt medium with 0.5% v/v Tapis crude oil as the sole carbon source. Crude oil biodegradation was measured by gas chromatography method. Five strains of pure microorganisms with petroleum degrading ability were isolated: three were bacteria and the other two were yeasts. Candida tropicalis strains 7Y and 15Y were identified as efficient oil degraders. Strain 15Y was more efficient, it was able to reduce 87.3% of the total petroleum or 99.6% of n-alkanes within the 7-day incubation period at room temperature of 25 ± 2 °C.     

Biodegradation and conversion of alkanes and crude oil by a marine Rhodococcus

A hydrocarbon degrader isolated from a chronically oil-polluted marine site was identified as Rhodococcus sp. on the basis of morphology, fatty acid methyl ester pattern, cell wall analysis, biochemical tests and G + C content of DNA. It degraded upto 50% of the aliphatic fraction of Assam crude oil, in seawater supplemented with 35 mM nitrogen as urea and 0.1 mM phosphorus as dipotassium hydrogen orthophosphate, after 72 h at 30 ° and 150 revolutions per minute. The relative percentage of intracellular fatty acid was higher in hydrocarbon-grown cells compared to fructose-grown cells. The fatty acids C₁₆ , C16_{16 :1} C₁₈ and C_{18 : 1} were constitutively present regardless of the growth substrate. In addition to these constitutive acids, other intracellular fatty acids varied in correlation to the hydrocarbon chain length supplied as a substrate. When grown on odd carbon number alkanes, the isolate released only monocarboxylic acids into the growth medium. On even carbon number alkanes only dicarboxylic acids were produced.     

Biodegradation of topped Kuwait crude

Summary Biodegradation of a topped Kuwait crude by a mixed microbial culture in a stirred tank fermenter was characterised by bursts of respiratory activity. Acinetobacter calcoaceticus var anitratus predominated during the degradation process. n-Alkanes were rapidly and completely removedlosses from other hydrocarbon classes were only partial. The products of the reaction were CO₂, biomass and oxidised hydrocarbon derivatives.     

饱和粘土中的三氯乙烯迁移特性

利用土柱模型以及吸附实验,分析不同ＮａＣｌ浓度情况下,三氯乙烯（ＴＣＥ）在蒙脱土和高岭土中的迁移特性．从实验中得到的等温吸附曲线表明,ＴＣＥ在蒙脱土中的吸附分配系数比在高岭土中的分配系数大３～８倍．由此可认为蒙脱上是一种可用于环境治理的天然材料．     

Biodegradation of a crude oil by three microbial consortia of different origins and metabolic capabilities

Microbial consortia were obtained three by sequential enrichment using different oil products. Consortium F1AA was obtained on a heavily saturated fraction of a degraded crude oil; consortium TD, by enrichment on diesel and consortium AM, on a mixture of five polycyclic aromatic hydrocarbons [PAHs]. The three consortia were incubated with a crude oil in order to elucidate their metabolic capabilities and to investigate possible differences in the biodegradation of these complex hydrocarbon mixtures in relation to their origin. The efficiency of the three consortia in removing the saturated fraction was 60% (F1AA), 48% (TD) and 34% (AM), depending on the carbon sources used in the enrichment procedures. Consortia F1AA and TD removed 100% of n-alkanes and branched alkanes, whereas with consortium AM, 91% of branched alkanes remained. Efficiency on the polyaromatic fraction was 19% (AM), 11% (TD) and 7% (F1AA). The increase in aromaticity of the polyaromatic fraction during degradation of the crude oil by consortium F1AA suggested that this consortium metabolized the aromatic compounds primarily by oxidation of the alkylic chains. The 500-fold amplification of the inocula from the consortia by subculturing in rich media, necessary for use of the consortia in bioremediation experiments, showed no significant decrease in their degradation capability. Journal of Industrial Microbiology & Biotechnology (2002) 28, 252–260 DOI: 10.1038/sj/jim/7000236 Received 12 July 2001/ Accepted in revised form 11 November 2001     

Biodegradation of Tapis blended crude oil in marine sediment by a consortium of symbiotic bacteria

Biodegradation rate and the high molecular weight hydrocarbons are among the important concerns for bioremediation of crude oil. Inoculation of a non-oil-degrading bacterium as supplementary bacteria increased oil biodegradation from 57.1% to 63.0% after 10 days of incubation. Both the oil-degrading bacteria and the non-oil-degrading bacteria were isolated from Malaysian marine environment. Based on the 16S rDNA sequences, the oil-degrading bacteria was identified as Pseudomonas pseudoalcaligenes (99% similarity) while the non-oil-degrading bacterium was Erythrobacter citreus (99% similarity). E. citreus does not grow on crude oil enriched medium under present experimental condition but it withstands 5000 mg kg^?1 Tapis blended crude oil in sediment. Under optimal condition, the oil-degrading bacterium; P. pseudoalcaligenes, alone utilized 583.3 ± 3.8 mg kg^?1 (57.1%) at the rate of 3.97 × 10^?10 mg kg^?1 cell^?1 day^?1 Tapis blended crude oil from 1000 mg kg^?1 oil-contaminated sediment. Inoculation of E. citreus as the supplementary bacteria to P. pseudoalcaligenes enhanced biodegradation. The bacterial consortium degraded 675.8 ± 18.5 mg kg^?1 (63.0%) Tapis blended crude oil from the 1000 mg kg^?1 oil-contaminated sediment. Biodegradation rate of the bacterial consortium increased significantly to 4.59 × 10^?10 mg kg^?1 cell^?1 day^?1 (p = 0.02). Improvement of the oil degradation by the bacterial consortium was due to the synergetic reaction among the bacterial inoculants. There are two implications: (1) E. citreus may have a role in removing self-growth-inhibiting compounds of P. pseudoalcaligens. (2) P. pseudoalcaligenes degraded Tapis blended crude oil while E. citreus competes for the partially degraded hydrocarbons by P. pseudoalcaligenes. P. pseudoalcaligenes forced to breakdown more hydrocarbons to sustain its metabolic requirement. The bacterial consortium degraded 78.7% of (C₁₂–C₃₄) total aliphatic hydrocarbons (TAHs) and 74.1% of the 16 USEPA prioritized polycyclic aromatic hydrocarbons.     

Biodegradation of wood in crude oil-polluted soil

A field investigation (April–November) in Nigeria showed that biodegradation of obeche (Triplochiton scleroxylon) wood blocks was initially retarded in crude oil-contaminated soil but later became enhanced as indicated by loss of compression resistance. Further indication of this pattern was the detection of soft-rot cavities and basidiomycete fungi after 2–3 months exposure when compared to control blocks in uncontaminated soil. Laboratory tests with Pleurotus sp., Trametes sp., Gloeophyllum sp. (basidiomycetes) and Chaetomium sp. (soft-rot fungus) confirmed that degradation of crude oil-coated obeche blocks was markedly retarded without the presence of hydrocarbon-degrading bacteria. The filtrate of hydrocarbon-degrading Pseudomonas sp. grown in mineral salt/crude oil medium for 3–4 weeks supported growth of the test fungi better than in carboxymethyl cellulose medium but less than in potato dextrose broth. Similarly, wood blocks immersed in the filtrate became significantly more susceptible to fungal degradation. Pseudomonas sp. from stationary phase growth in crude oil medium depleted residual sugar in basidiomycete-degraded sawdust with a concomitant marked increase in its population. It may be concluded that readily metabolizable products of crude oil degradation by soil organisms and the removal of residual sugar which may have prevented catabolite repression of cellulases, culminated in increased attack on the wood by soil-borne wood-decomposing organisms.     

Biodegradation of phenanthrene by Pseudomonas sp. BZ-3, isolated from crude oil contaminated soil

A phenanthrene (PHE) degrading bacterium strain BZ-3 was isolated from the crude oil contaminated soil in Binzhou, China. The isolate was identified as Pseudomonas sp. BZ-3 on the basis of 16S rRNA gene sequence. Various experiments were conducted to investigate the effect of pH, salinity and PHE concentration on the degradation efficiency of PHE. The degradation efficiency and degradation metabolites of PHE were detected by using GC–MS and HPLC-MS analyses. The strain BZ-3 could degrade 75% of PHE at an initial concentration of 50 mg/L under 20 g/L salinity in 7 days. PHE degradation kinetics was estimated in a first-order degradation rate model and the rate coefficient was calculated as 0.108 d⁻¹. On the basis of the identified degradation metabolites, the strain BZ-3 could degrade PHE in the salicylate metabolic pathway. In a mixture system consisting of PHE and other PAHs including naphthalene (NA), anthracene (ANTH), and pyrene (PYR), the strain BZ-3 showed an efficiently degradation capability. Further study showed that the strain BZ-3 could also use NA, ANTH, PYR, xylene, 1-hydroxy-2-naphthoic acid, and hexane as the sole carbon and energy source, but did not grow on nitrobenzene-containing medium.     

Biodegradation of crude oil and pure hydrocarbons by extreme halophilic archaea from hypersaline coasts of the Arabian Gulf

Two extreme halophilic Haloferax strains and one strain each of Halobacterium and Halococcus were isolated from a hypersaline coastal area of the Arabian Gulf on a mineral salt medium with crude oil vapor as a sole source of carbon and energy. These archaea needed at least 1 M NaCl for growth in culture, and grew best in the presence of 4 M NaCl or more. Optimum growth temperatures lied between 40 and 45oC. The four archaea were resistant to the antibiotics chloramphenicol, cycloheximide, nalidixic acid, penicillin, streptomycin and tetracycline. The strains could grow on a wide scope of aliphatic and aromatic (both mono-and polynuclear) hydrocarbons, as sole sources of carbon and energy. Quantitative measurements revealed that these extreme halophilic prokaryotes could biodegrade crude oil (13–47%, depending on the strain and medium salinity), n-octadecane (28–67%) and phenanthrene (13–30%) in culture after 3 weeks of incubation. The rates of biodegradation by all strains were enhanced with increasing NaCl concentration in the medium. Optimal concentration was 3 M NaCl, but even with 4 M NaCl the hydrocarbon-biodegradation rates were higher than with 1 and 2 M NaCl. It was concluded that these archaea could contribute to self-cleaning and bioremediation of oil-polluted hypersaline environments.     

Biodegradation of engine oil in soil

Laboratory experiments were conducted with the aim of bioremediation of sandy soil from engine oil in 5% concentration. Bacterial strains, active in degrading oil hydrocarbons as a sole source of carbon and energy were selected and identified. Optimal parameters, such as concentration of inorganic nutrients (expressed as C:N and C:P ratio) and the size of inoculum were established in experiments on 1% engine oil biodegradation. Process enhancing role of surfactants addition, the application of immobilized biomass and reinoculations was also evaluated.     

Corticosteroid and thyroid responses of larval and juvenile turbot exposed to the water-soluble fraction of crude oil

Turbot larvae (24–590 degree C days; 2–32 days post-hatch) and juveniles (1345 degree C days; 98 days post-hatch), were exposed for 6 h to 25, 33 and 50% water-soluble fraction (WSF) of crude oil in either static or flow-through test systems. Larvae showed generalized primary endocrine responses, identified by elevated whole body cortisol content from as early as 2 days post-hatch. In older larvae and juveniles, the response was related to the WSF concentration. This dose-response relationship was not apparent in younger and yolk-sac larvae. Whole body thyroxine content of turbot larvae exposed to the WSF of crude oil was increased, but triiodothyronine content remained stable. Aromatic hydrocarbon concentrations [benzene, toluene, ethylbenzene and xylene (BTEX) and naphthalenes] remained constant during flow-through tests, but 65% of the initial level of BTEX hydrocarbons and 40% of the naphthalenes were lost during static exposures. Larval mortalities increased with exposure to an increasing concentration of crude oil WSF. Larval activity was significantly reduced even at the lowest WSF concentration.     

Effects of nitrogen source on crude oil biodegradation

Summary The effects of NH₄Cl and KNO₃ on biodegradation of light Arabian crude oil by an oil-degrading enrichment culture were studied in respirometers. In poorly buffered sea salts medium, the pH decreased dramatically in cultures that contained NH₄Cl, but not in those supplied with KNO₃. The ammonia-associated pH decline was severe enough to completely stop oil biodegradation as measured by oxygen uptake. Regular adjustment of the culture pH allowed oil biodegradation to proceed normally. A small amount of nitrate accumulated in all cultures that contained ammonia, but nitrification accounted for less than 5% of the acid that was observed. The nitrification inhibitor, nitrapyrin, had no effect on the production of nitrate or acid in ammonia-containing cultures. When the culture pH was controlled, either by regular adjustment of the culture pH or by supplying adequate buffering capacity in the growth medium, the rate and extent of oil biodegradation were similar in NH₄Cl- and KNO₃-containing cultures. the lag time was shorter in pH-controlled cultures supplied with ammonia than in nitrate-containing cultures.     

Biodegradation of petroleum-based oil wastes through composting

Composting of horse manure was used as a means of degradation of two oil wastes, oil sludge from petrol stations and petroleum residues from a refinery. Paraffin oil was chosen as a reference. Oil wastes decomposed to 78–93% during 4.5 months of composting. The degradation of the waste oils was higher than that of the reference paraffin oil and no difference was found between the two types of oil wastes concerning their decomposition. At the end of the experiment, most of the polyaromatic hydrocarbons had been degraded except pyrene, chrysene and dibenz(ah)anthracene. Gaseous losses of oil compounds through volatilisation from composts were found not to be significant.     

Biological upgrading of heavy crude oil

Heavy crudes (bitumen) are extremely viscous and contain high concentrations of asphaltene, resins, nitrogen and sulfur containing heteroaromatics and several metals, particularly nickel and vanadium. These properties of heavy crude oil present serious operational problems in heavy oil production and downstream processing. There are vast deposits of heavy crude oils in many parts of the world. In fact, these reserves are estimated at more than seven times the known remaining reserves of conventional crude oils. It has been proven that reserves of conventional crude oil are being depleted, thus there is a growing interest in the utilization of these vast resources of unconventional oils to produce refined fuels and petrochemicals by upgrading. Presently, the methods used for reducing viscosity and upgradation is cost intensive, less selective and environmentally reactive. Biological processing of heavy crudes may provide an ecofriendly alternative or complementary process with less severe process conditions and higher selectivity to specific reactions to upgrade heavy crude oil. This review describes the prospects and strengths of biological processes for upgrading of heavy crude oil.     

Corrosion of Pembina crude oil pipeline

Summary Corrosion failure of the Pembina pipeline system of North Central Alberta, Canada, was frequent and was associated with constant bacterial load and sulphide in the crude oil and produced water. The bacterial load included a variety of anaerobic and aerobic/facultative bacteria which acted in concert to produce sulphide, giving rise to a cascade of sulphide generation.A total of 256 isolates from the crude oil were tested for ability to reduce oxidized sulphur compounds to sulphide. Five groups of bacteria, (A-E), based on this ability to reduce sulphur compounds, existed in the crude oil system. Group A reduced sulphur compounds with oxidation states +6; and lower, Group B reduced oxidation state +4 and below; Group C, oxidation states +2 and lower. Group D reduced only oxidation state 0 (elemental Sulphur), while Group E could reduce no sulphur compound to sulphide. It was found that a ceiling on the reductive capability of each bacterial group was set by the oxidation state of the sulphur compounds. The result is a synergistic relationship whereby intermediate products of reductive activities of each group form the substrate for subsequent action by other groups until sulphide is produced.     

Endocrine, osmoregulatory, respiratory and haematological parameters in flounder exposed to the water soluble fraction of crude oil

Flounders Pleuronectes flesus with an implanted vascular catheter were exposed to a 50% dilution of the water soluble fraction (WSF) of Omani crude oil (c. 6ppm total aromatic hydrocarbons) and serial blood samples taken to determine their endocrine status (cortisol, catecholamines and thyroid hormones) and the resultant and/or causal physiological (haematological, ionoregulatory and respiratory) disturbances. This resulted in a progressive increase in plasma cortisol concentrations from 3 h onwards (rising from 18 to 51 ng ml⁻¹ after 48-h exposure), and increased plasma glucose concentrations indicating a generalized stress response. Plasma T3 and T4 concentrations of both control and WSF-exposed groups declined progressively over the experimental period; exposure to the WSF of crude oil further depressed plasma T4 concentrations but not plasma T₃ concentrations relative to those of control fish. Plasma osmolality and sodium and chloride concentrations were stable in WSF-exposed fish, however, plasma potassium concentrations were increased significantly at the 24-and 48-h sampling points. The most profound physiological disturbance in WSF-exposed fish was a dramatic decline in blood oxygen content (CvO₂) (from 2–8 to 0–8 ml 100 ml⁻¹ after 48-h exposure), which is likely to be the cause of the increased plasma noradrenaline concentrations from 3 h onwards. Increased noradrenaline is likely in turn to have been responsible for the significant increase in blood haematocrit and blood haemoglobin at the 3-h sampling point, although the dominant effect in the longer-term was a significant decline in both of these haematological parameters.     

Individual to population level effects of South Louisiana crude oil water accommodated hydrocarbon fraction (WAF) on a marine meiobenthic copepod

Acute toxicities of crude oil and crude oil water accommodated hydrocarbon fraction (WAF) are relatively well documented, but data on the biological effects of chronic exposures to WAF on species and populations are scarce. South Louisiana Sweet crude oil was used to assess the effects of crude oil WAF on the copepod Amphiascus tenuiremis' survival, development and reproduction. Effects were evaluated using a 96-well microplate full life-cycle toxicity test, a test that allows tracking of individuals from the nauplius stage to sexual maturation and reproduction. Briefly, 24-h hatched nauplii were followed to adulthood (n_i = ≥ 120 nauplii/treatment) in individual glass-coated microplate wells containing 200 μL of seawater solution. Treatments consisted of 10%, 30%, 50% and 100% Louisiana WAF, with seawater used as control. Nauplii were monitored through development to adulthood, and sexually mature virgin copepods were mated pairwise in wells containing original rearing treatments. Nauplius-to-copepodite survival was reduced by 57% in exposures to 100% WAF, relative to controls (88 ± 3%), and copepodite-to-adult survival was reduced by 18% in the 50% WAF, relative to controls (98 ± 3%). Analysis of development curves showed that nauplii in the 10% WAF developed significantly faster into copepodites, while nauplii in the 50% WAF developed significantly slower than controls. Although the naupliar developmental rate in the 100% WAF was not significantly different from the control, these nauplii showed an average 1.4 day delay in development into copepodites. Similarly, copepodite development into mature females and males was significantly enhanced by 1.2 to 1.8 days and delayed by 1.9 to 2.2 days (p < 0.05) in the 10% and 50% WAFs, respectively, compared to controls. Although the copepodite developmental rate in the 100% WAF was not significantly different from the control, these copepodites still showed an average 1.5 and 2.1 day delay in development into females and males, respectively. Analysis of reproductive endpoints showed that fertility was the only endpoint negatively affected by WAFs; reproductive failure increased by 30% and 41% in exposures to 30% and 100% WAF, respectively, compared to controls (3.33 ± 4.71%). Leslie matrix population projections based on empirical microplate data indicated lower production rates through three generations of exposure to WAFs. Furthermore, a comparison between NIST and Louisiana crude oil WAFs using the same life-cycle approach indicated a greater chronic toxicity for the Louisiana WAF and an overall developmental delay in exposures to high WAFs (50% and 100% WAFs) from both crude oil types.     

Biodegradation of crude oil across a wide range of salinities by an extremely halotolerant bacterial consortium MPD-M,immobilized onto polypropylene fibers

The bacterial consortium MPD-M, isolated from sediment associated with Colombian mangrove roots, was effective in the treatment of hydrocarbons in water with salinities varying from 0 to 180 g L(-1). Where the salinity of the culture medium surpassed 20 g L(-1), its effectiveness increased when the cells were immobilized on polypropylene fibers. Over the range of salinity evaluated, the immobilized cells significantly enhanced the biodegradation rate of crude oil compared with free-living cells, especially with increasing salinity in the culture medium. Contrary to that observed in free cell systems, the bacterial consortium MPD-M was highly stable in immobilized systems and it was not greatly affected by increments in salinity. Biodegradation was evident even at the highest salinity evaluated (180 g L(-1)), where biodegradation was between 4 and 7 times higher with immobilized cells compared to free cells. The biodegradation of pristane (PR) and phytane (PH) and of the aromatic fraction was also increased using cells immobilized on polypropylene fibers.     

Immobilization of bacteria on polymer matrices for degradation of crude oil and oil products

Organic polymer materials (OPM) differing in sets of functional groups, fiber surface thickness and character, and density of fiber packing in fabric were synthesized. OPM were studied for assessing the possibility of their application as sorbents for oil spills in water bodies. The synthesized OPM were used for the creation of bio-hybrid materials as matrices for immobilization of bacteria of the genus Rhodococcus sp. capable of petroleum degradation. Actively dividing bacterial cells forming clusters were shown to be present at the surface of fibers. Active attachment of the cells to polymeric surface due to intrusion and/or excretion of extracellular biopolymeric matrix were detected. The modification of polymer sorbents was shown to influence bacterial immobilization. The peculiarity of growth and the specificity of cell morphology of bacterial culture were noted.