Biodegradation of Crude Oil by Individual Bacterial Strains and a Mixed Bacterial Consortium Isolated from Hydrocarbon Contaminated Areas

A preliminary study was undertaken to determine the optimal conditions for the biodegradation of a crude oil. Among 57 oil‐degrading bacterial cultures isolated from oil‐contaminated soil samples, Bacillus sp. IOS1‐7, Corynebacterium sp. BPS2‐6, Pseudomonas sp. HPS2‐5, and Pseudomonas sp. BPS1‐8 were selected for the study based on the efficiency of crude oil utilization. Along with the selected individual strains, a mixed bacterial consortium prepared using the above strains was also used for degradation studies. The mixed bacterial consortium showed more growth and degradation than did individual strains. At 1% crude oil concentration, the mixed bacterial consortium degraded a maximum of 77% of the crude oil. This was followed by 69% by Pseudomonas sp. BPS1‐8, 64% by Bacillus sp. IOS1‐7, 45% by Pseudomonas sp. HPS2‐5, and 41% by Corynebacterium sp. BPS2‐6. The percentage of degradation by the mixed bacterial consortium decreased from 77 to 45% as the concentration of crude oil was increased from 1 to 12%. Temperature of 35°C and pH 7 were found to be optimum for maximum degradation.     

Isolation and characterization of two crude oil-degrading yeast strains, Yarrowia lipolytica PG-20 and PG-32, from the Persian Gulf

Among six crude oil-degrading yeasts that were isolated from an oil-polluted area in the Persian Gulf, two yeast strains showed high degradation activity of aliphatic hydrocarbons. From an analysis of 18S rRNA sequences and biochemical characteristics, these strains were identified as Yarrowia lipolytica strains PG-20 and PG-32. Gas Chromatography (GC) analysis of the crude oil remaining in the culture medium after 1 week at 30°C showed that the strains PG-20 and PG-32 degraded 68% and 58% of crude oil, respectively. The optimal growth condition and biodegradation of hydrocarbons was in ONR medium with an acidic pH (pH5). These two strains may degrade aliphatic hydrocarbons more efficiently than aromatic hydrocarbons, although strain PG-20 had better degradation than strain PG-32. The two Y. lipolytica strains reduce surface tension when cultured on hydrocarbon substrates (1% v/v). These strains showed a cell surface hydrophobicity higher than 70%. These results suggested that Y. lipolytica strains PG-20 and PG-32 have high crude oil degrading activity due to their high emulsifying activity and cell hydrophobicity. In conclusion, these yeast strains can be useful for the bioremediation process in the Persian Gulf and decreasing oil pollution in this marine ecosystem.     

The flavour and chemical assessment of dabs (Limanda limanda) caught in the vicinity of the Beatrice Oil Platform

Dabs (Limanda limanda) caught in close proximity to the Beatrice Oil Platform have been assessed for the presence of an oil taint and chemically analysed for n-alkane and polynuclear aromatic hydrocarbons.Although contamination from petrogenic hydrocarbons was apparent, none of the fish were found to have a definite taint.     

Isolation and characterization of a novel hydrocarbon-degrading bacterium Achromobacter sp. HZ01 from the crude oil-contaminated seawater at the Daya Bay,southern China

Microorganisms play an important role in the biodegradation of petroleum contaminants, which have attracted great concern due to their persistent toxicity and difficult biodegradation. In this paper, a novel hydrocarbon-degrading bacterium HZ01 was isolated from the crude oil-contaminated seawater at the Daya Bay, South China Sea, and identified as Achromobacter sp. Under the conditions of pH 7.0, NaCl 3% (w/v), temperature 28 °C and rotary speed 150 rpm, its degradability of the total n-alkanes reached up to 96.6% after 10 days of incubation for the evaporated diesel oil. Furthermore, Achromobacter sp. HZ01 could effectively utilize polycyclic aromatic hydrocarbons (PAHs) as its sole carbon source, and could remove anthracene, phenanthrene and pyrence about 29.8%, 50.6% and 38.4% respectively after 30 days of incubation. Therefore, Achromobacter sp. HZ01 may employed as an excellent degrader to develop one cost-effective and eco-friendly method for the bioremediation of marine environments polluted by crude oil.     

Survival of two species of amphipods in aqueous extracts of petroleum oils

Aqueous extracts of two petroleum oils, No. 2 fuel oil and Southern Louisiana crude, were tested on two amphipods, Gammarus muccronatus and Amphithoe valida, for survival. The oils were toxic at concentrations of 0.8 ppm (fuel oil) and 2.4 ppm (S. Louisiana crude). Mortalities increased with the concentration and length of exposure. Few or no young were produced at these and higher concentrations (breeding adults were decreasing rapidly in numbers). The amphipods are more sensitive to aqueous extracts of these oils than benthic polychaetes and shrimp, for which data are available.     

The effect of volatile components in oil on evolutionary characteristics of diamondoids during oil thermal pyrolysis

On the basis of the results of simulation experiments, now we better understand the contribution of high carbon number hydrocarbons to diamondoid generation during thermal pyrolysis of crude oil and its sub-fractions(saturated, aromatic, resin, and asphalene fractions). However, little is known about the effect of volatile components in oil on diamondoid generation and diamondoid indices due to the lack of attention to these components in experiments. In this study, the effect of volatile components in oil on diamondoid generation and maturity indices was investigated by the pyrolysis simulation experiments on a normal crude oil from the HD23 well of the Tarim Basin and its residual oil after artificial volatilization, combined with quantitative analysis of diamondoids. The results indicate that the volatile components(≤n C12) in oil have an obvious contribution to the generation of adamantanes, which occurs mainly in the early stage of oil cracking(Easy Ro1.0%), and influences the variations in maturity indices of adamantanes; but they have no obvious effect on the generation and maturity indices of diamantanes. Therefore, some secondary alterations e.g., migration, gas washing, and biodegradation, which may result in the loss of light hydrocarbons in oil under actual geological conditions, could affect the identification of adamantanes generated during the late-stage cracking of crude oil, and further influence the practical application of adamantane indices.     

The bacterial community composition of an active oil field in the northwestern Gulf of Mexico

The bacterial composition of the water column around two oil production platforms and a control site was examined. Samples were collected during three seasons of a 12-month sampling period three water depths were sampled at all stations occupied.No major differences were discovered in taxonomic or physiological makeup of bacterial populations of the oil field and control site. The genus Pseudomonas predominated at the oil field stations and the control. Bacterial numbers were lower for oil field stations than the control and generally decreased with depth. Microbial biomass estimates were consistently higher at the control site. Oil degrading and sulphur oxidizing bacteria were more numerous within the oil field, and their numbers decreased with distance from the platforms. Buccaneer crude oil did not adversely affect growth or attachment ability of oil field isolates.     

Role of a moderately halophilic bacterial consortium in the biodegradation of polyaromatic hydrocarbons

Polycyclic aromatic hydrocarbons are ubiquitous pollutants in the environment, and most high molecular weight PAHs cause mutagenic, teratogenic and potentially carcinogenic effects. While several strains have been identified that degrade PAHs, the present study is focused on the degradation of PAHs in a marine environment by a moderately halophilic bacterial consortium. The bacterial consortium was isolated from a mixture of marine water samples collected from seven different sites in Chennai, India. The low molecular weight (LMW) PAHs phenanthrene and fluorine, and the high molecular weight (HMW) PAHs pyrene and benzo(e)pyrene were selected for the degradation study. The consortium metabolized both LMW and HMW PAHs. The consortium was also able to degrade PAHs present in crude oil-contaminated saline wastewater. The bacterial consortium was able to degrade 80% of HMW PAHs and 100% of LMW PAHs in the saline wastewater. The strains present in the consortium were identified as Ochrobactrum sp., Enterobacter cloacae and Stenotrophomonas maltophilia. This study reveals that these bacteria have the potential to degrade different PAHs in saline wastewater.     

Potential petroleum sources and exploration directions around the Manjar Sag in the Tarim Basin

Since the discovery of the Tahe oilfield, it has been controversial on whether the main source rock is in the Cambrian or Middle-Upper Ordovician strata. In this paper, it is assumed that the crude oil from the Wells YM 2 and TD 2 was derived from the Middle-Upper Ordovician and Cambrian source rocks, respectively. We analyzed the biomarkers of the crude oil, asphalt-adsorbed hydrocarbon and saturated hydrocarbon in bitumen inclusions from the Lunnan and Hade areas in the North Uplift of the Tarim Basin. Results show that the ratios of tricyclic terpane C₂₁/C₂₃ in the crude oil, asphalt-adsorbed hydrocarbon and saturated hydrocarbon in bitumen inclusions are less than 1.0, indicating that they might be from Upper Ordovician source rocks; the ratios of C₂₈/(C₂₇+C₂₈+C₂₉) steranes in the saturated hydrocarbon from reservoir bitumen and bitumen inclusions are higher than 25, suggesting that they might come from the Cambrian source rocks, however, the ratios of C₂₈/(C₂₇+C₂₈+C₂₉) steranes in oil from the North Uplift are less than 25, suggesting that they might be sourced from the Upper Ordovician source rocks. These findings demonstrate that the sources of crude oil in the Tarim Basin are complicated. The chemical composition and carbon isotopes of Ordovician reservoired oil in the Tarim Basin indicated that the crude oil in the North Uplift (including the Tahe oilfield) and Tazhong Depression was within mixture areas of crude oil from the Wells YM 2 and TD 2 as the end members of the Cambrian and Middle-Upper Ordovician sourced oils, respectively. This observation suggests that the crude oil in the Ordovician strata is a mixture of oils from the Cambrian and Ordovician source rocks, with increasing contribution from the Cambrian source rocks from the southern slope of the North Uplift to northern slope of the Central Uplift of the Tarim Basin. Considering the lithology and sedimentary facies data, the spatial distribution of the Cambrian, Middle-Lower Ordovician and Upper Ordovician source rocks was reconstructed on the basis of seismic reflection characteristics, and high-quality source rocks were revealed to be mainly located in the slope belt of the basin and were longitudinally developed over the maximum flooding surface during the progressive-regressive cycle. Affected by the transformation of the tectonic framework in the basin, the overlays of source rocks in different regions are different and the distribution of oil and gas was determined by the initial basin sedimentary structure and later reformation process. The northern slope of the Central Uplift-Shuntuo-Gucheng areas would be a recent important target for oil and gas exploration, since they have been near the slope area for a long time.     

Isolation and characterization of alkane degrading bacteria from petroleum reservoir waste water in Iran (Kerman and Tehran provenances)

Petroleum products spill and leakage have become two major environmental challenges in Iran. Sampling was performed in the petroleum reservoir waste water of Tehran and Kerman Provinces of Iran. Alkane degrading bacteria were isolated by enrichment in a Bushnel–Hass medium, with hexadecane as sole source of carbon and energy. The isolated strains were identified by amplification of 16S rDNA gene and sequencing. Specific primers were used for identification of alkane hydroxylase gene. Fifteen alkane degrading bacteria were isolated and 8 strains were selected as powerful degradative bacteria. These 8 strains relate to Rhodococcus jostii, Stenotrophomonas maltophilia, Achromobacter piechaudii, Tsukamurella tyrosinosolvens, Pseudomonas fluorescens, Rhodococcus erythropolis, Stenotrophomonas maltophilia, Pseudomonas aeruginosa genera. The optimum concentration of hexadecane that allowed high growth was 2.5%. Gas chromatography results show that all strains can degrade approximately half of hexadecane in one week of incubation. All of the strains have alkane hydroxylase gene which are important for biodegradation. As a result, this study indicates that there is a high diversity of degradative bacteria in petroleum reservoir waste water in Iran.     

Screening of biosurfactant producers from petroleum hydrocarbon contaminated sources in cold marine environments

An overview of literature about isolating biosurfactant producers from marine sources indicated no such producers have been reported form North Atlantic Canada. Water and sediment samples were taken from petroleum hydrocarbon contaminated coastal and offshore areas in this region. Either n-hexadecane or diesel was used as the sole carbon source for the screening. A modified colony-based oil drop collapsing test was used to cover sessile biosurfactant producers. Fifty-five biosurfactant producers belong to genera of Alcanivorax, Exiguobacterium, Halomonas, Rhodococcus, Bacillus, Acinetobacter, Pseudomonas, and Streptomyces were isolated. The first three genera were established after 1980s with interesting characteristics and limited relevant publications. Some of the 55 isolated strains were found with properties such as greatly reducing surface tension, stabilizing emulsion and producing flocculant. Isolates P6-4P and P1-5P were selected to demonstrate the performance of biosurfactant production, and were found to reduce the surface tension of water to as low as 28 dynes/cm.     

The effect of petroleum hydrocarbons on reproduction of an estuarine planktonic copepod in laboratory cultures

The effect of short-term exposure to high concentration (mg l.^?1) of water soluble fraction of aromatic heating oil on subsequent egg production by the estuarine copepod Eurytemora affinis has been studied in laboratory cultures to investigate possibly sublethal biological effects following exposure to hydrocarbon under an oil spill. Significant reduction in subsequent length of life, total number of eggs produced, mean brood size, and rate of egg production was observed. Exposure to naphthalene alone at 1 mg l.^?1 for 24 h produced a significant effect on total fecundity of the females. Ingestion rates were significantly lower when measured in the presence of the water soluble fraction, and also naphthalene alone at mg l.^?1 concentrations. Exposure to low-levels (10 and 50 μg l.^?1) of ¹⁴C-naphthalene alone over a period of ten days produced no significant effect on feeding or reproduction despite the high concentrations of hydrocarbon accumulated during this period. The results are discussed in relation to previous work on the fate of hydrocarbons in planktonic copepods, using ¹⁴C-1-naphthalene as a model compound.     

Hydrocarbon degraders from tropical marine environments

Analysis of 20 samples of marine mud and water around Mumbai resulted in the isolation of 17 bacteria and yeasts all of which were able to degrade more than 10% of the supplied crude oil. The yeasts strains were important degraders of the aliphatic fraction of crude. All the isolated yeasts belonged to the genus Candida. Using biochemical tests these were identified as Candida parapsilosis, C. albicans, C. guilliermondii, Yarrowia lipolytica, C. tropicalis and C. intermedia. Y. lipolytica was the best degrader utilizing 78% of the aliphatic fraction of Bombay High crude oil. None of these isolates degraded the aromatic or ashphaltene fractions. All the isolates required aeration, nitrogen and phosphate supplementation for optimal degradation. Four out of the six yeasts are human pathogens.     

The recognition of biodegraded petroleum-derived aromatic hydrocarbons in recent marine sediments

Aromatic hydrocarbon fractions isolated from sediments polluted with crude oil, from sampling stations in and around Sullom Voe, Shetland Islands, were found to exhibit, as the major feature in their gas chromatograms, an unresolved complex mixture or ‘hump’. This feature was absent from the gas chromatograms of the aromatic hydrocarbon fractions isolated from corresponding unpolluted sediments in the region. The observed aromatic hump had little resemblance to the distribution of aromatic hydrocarbons in a typical North Sea crude oil. Incubation studies, however, showed that such a hump was appearing when oil-spiked sediments were aerobically biodegraded. From these incubation studies it was also evident that alkylaromatic hydrocarbons in the crude oil were biodegraded before any change in the normal alkanes was apparent. Therefore, the presence of an unresolved complex mixture in the gas chromatograms of aromatic hydrocarbon fractions from recent sediments can act as a marker to recognize contamination by crude oil.     

Biodegradation of petroleum hydrocarbons at low temperature in the presence of the dispersant Corexit 9500

Our study examined the effects of Corexit 9500 and sediment on microbial mineralization of specific aliphatic and aromatic hydrocarbons found in crude oil. We also measured gross mineralization of crude oil, dispersed crude oil and dispersant by a marine microbial consortium in the absence of sediment. When provided as carbon sources, our consortium mineralized Corexit 9500 the most rapidly, followed by fresh oil, and finally weathered oil or dispersed oil. However, mineralization in short term assays favored particular components of crude oil (2-methyl-naphthalene > dodecane > phenanthrene > hexadecane > pyrene) and was not affected by addition of nutrients or sediment (high sand, low organic carbon). Adding dispersant inhibited hexadecane and phenanthrene mineralization but did not affect dodecane and 2-methyl-naphthalene mineralization. Thus, the effect of dispersant on biodegradation of a specific hydrocarbon was not predictable by class. The results were consistent for both high and low oiling experiments and for both fresh and weathered oil. Overall, our results indicate that environmental use of Corexit 9500 could result in either increases or decreases in the toxicity of residual oil through selective microbial mineralization of hydrocarbons.     

Isolation and characterization of crude-oil-degrading bacteria from the Persian Gulf and the Caspian Sea

Twenty-five crude-oil-degrading bacteria were isolated from oil-contaminated sites in the Persian Gulf and the Caspian Sea. Based on a high growth rate on crude oil and on hydrocarbon degradation ability, 11 strains were selected from the 25 isolated strains for further study. Determination of the nucleotide sequence of the 16S rRNA gene showed that these isolated strains belonged to genera Acinetobacter, Pseudomonas, Gordonia, Rhodococcus, Cobetia, Halomonas, Alcanivorax, Marinobacter and Microbacterium. Among the 11 isolates, strains BS (Acinetobacter calcoaceticus, 98%) and PG-12 (Alcanivorax dieselolei, 98%) were the most effective in degrading crude oil. Rate of crude-oil degradation of 82% (isolate BS) and 71% (isolate PG-12) were observed after 1 week of cultivation in mineral medium. These strains had high emulsification activity and biosurfactant production. GC-MS analysis showed that A. dieselolei PG-12 can degrade different alkanes in crude oil. Screening of the distribution of the alkane hydroxylase gene in 25 isolates in relation to the source of isolation indicated that the group (II) alkane hydroxylase is prevalent in the Caspian Sea, but in the Persian Gulf, the frequency of the group (III) alkane hydroxylase gene is greater than that of the group (II) alkane hydroxylase gene.     

Analysis of community structure of a microbial consortium capable of degrading benzo(a)pyrene by DGGE

A microbial consortium was obtained by enrichment culture of sea water samples collected from Botan oil port in Xiamen, China, using the persistent high concentration of a mixture of polycyclic aromatic hydrocarbons enrichment strategy. Denaturing gradient gel electrophoresis (DGGE) was used to investigate the bacterial composition and community dynamic changes based on PCR amplification of 16S rRNA genes during batch culture enrichment. Using the spray-plate method, three bacteria, designated as BL01, BL02 and BL03, which corresponded to the dominant bands in the DGGE profiles, were isolated from the consortium. Sequence analysis showed that BL01, BL02 and BL03 were phylogenetically close to Ochrobactrum sp., Stenotrophomonas maltophilia and Pseudomonas fluorescens, respectively. The degradation of benzo(a)pyrene (BaP), a model high-molecular-weight polycyclic aromatic hydrocarbon (HMW PAH) compound was investigated using individual isolates, a mixture of the three isolates, and the microbial consortium (BL) originally isolated from the oil port sea water. Results showed that the order of degradative ability was BL > the mixture of the three isolates > individual isolates. BL degraded 44.07% of the 10 ppm BaP after 14 days incubation, which showed the highest capability for HMW PAH compound degradation.Our results revealed that this high selective pressure strategy was feasible and effective in enriching the HMW PAH-degraders from the original sea water samples.     

Cracking conditions of crude oil under different geological environments

There are mainly 3 kinds of existing states of oil generating from source rocks, that is, dispersive liquid hydrocarbon inside of source rock, dispersive liquid hydrocarbon outside of source rock and concentrated liquid hydrocarbon outside of source rock. Because of the differences in thermal history and medium conditions around, and the interaction of organic and inorganic matter, the liquid hydrocarbon with 3 kinds of existing state has different cracking conditions. The gas generation dynamics experiments of crude oil matching different mediums indicate that the distribution of activation energy of methane changes a lot according to medium difference. The carbonate has a main influence on oil cracking conditions and can largely reduce its activation energy, which reflects the lower cracking temperature of crude oil. The mudstone takes a second place and the sandstone is the smallest. The catalytic cracking function to the oil of the carbonate, of the mudstone and of the sandstone changes weaken in turn. The corresponding R _o values of main gas generation period in different mediums are as follows: 1.5%–3.8% with pure crude oil, 1.2%–3.2% with dispersive crude oil in carbonate, 1.3%～3.4% with dispersive crude oil in mudstone and 1.4%–3.6% with dispersive crude oil in sandstone. The influence of pressure to crude oil cracking is relatively complicated. In the low heating speed condition, pressure restrains the oil cracking and gas generation, but in the high heating speed condition, pressure has an indistinctive influence to the oil cracking and gas generation. Pressure also makes a different effort in different evolvement stage. Taking the middle and lower Cambrian source rocks in the Tarim Basin as an example, primary oil generating quantity is 2232.24×10⁸t, residual oil and oil cracking gas quantity is 806.21×10⁸t and 106.95×10¹²m³ respectively.     

Compound-specific stable carbon isotopic composition of petroleum hydrocarbons as a tool for tracing the source of oil spills

With the increasing demand for and consumption of crude oils, oil spill accidents happen frequently during the transportation of crude oils and oil products, and the environmental hazard they pose has become increasingly serious in China. The exact identification of the source of spilled oil can act as forensic evidence in the investigation and handling of oil spill accidents. In this study, a weathering simulation experiment demonstrates that the mass loss of crude oils caused by short-term weathering mainly occurs within the first 24h after a spill, and is dominated by the depletion of low-molecular weight hydrocarbons (相似文献   

Effects of surface and sunken crude oil on the behaviour of a sea urchin

Studies have been made of the effects of exposure to various forms of crude oil on the righting behaviour of Paracentrotus lividus and its reactions towards the presence of oil. Prolongation of the righting response was recorded in animals exposed to contact with surface or sunken fresh crude oil or to their water soluble fractions. No such effect was recorded on exposure to weathered oils and results indicate that the more volatile components of crude oil were responsible for this effect. Paracentrotus showed no avoidance reaction to the presence of sunken oil in its vicinity. The likely ecological significance of these results is discussed.