Isolation and characterization of a potential paraffin-wax degrading thermophilic bacterial strain Geobacillus kaustophilus TERI NSM for application in oil wells with paraffin deposition problems

A novel alkane monooxygenase evolved from a broken piece of ribonucleotide reductase in Geobacillus kaustophilus HTA426 isolated from Mariana Trench

We have accidentally found that a thermophilic Geobacillus kaustophilus HTA426 is capable of degrading alkanes although it has no alkane oxygenating enzyme genes. Our experimental results revealed that a putative ribonucleotide reductase small subunit GkR2loxI (GK2771) gene encodes a novel heterodinuclear Mn-Fe alkane monooxygenase/hydroxylase. GkR2loxI protein can perform two-electron oxidations similar to homonuclear diiron bacterial multicomponent soluble methane monooxygenases. This finding not only answers a long-standing question about the substrate of the R2lox protein clade, but also expands our understanding of the vast diversity and new evolutionary lineage of the bacterial alkane monooxygenase/hydroxylase family.

In situ bioremediation of petroleum hydrocarbon–contaminated soil: isolation and application of a Rhodococcus strain

Due to low consumption and high efficiency, in situ microbial remediation of petroleum hydrocarbons (PHs)-contaminated sites in in-service petrochemical enterprises has attracted more and more attention. In this study, a degrading strain was isolated from oil depot-contaminated soil with soil extract (PHs) as the sole carbon source, identified and named Rhodococcus sp. OBD-3. Strain OBD-3 exhibited wide adaptability and degradability over a wide range of temperatures (15-37 °C), pH (6.0-9.0), and salinities (1-7% NaCl) to degrade 60.6-86.6% of PHs. Under extreme conditions (15 °C and 3-7% salinity), PHs were degraded by 60.6 ± 8.2% and more than 82.1% respectively. In OBD-3, the alkane monooxygenase genes alkB1 and alkB2 (GenBank accession numbers: MZ688386 and MZ688387) were found, which belonged to Rhodococcus by sequence alignment. Moreover, strain OBD-3 was used in lab scale remediation in which the contaminated soil with OBD-3 was isolated as the remediation object. The PHs were removed at 2,809 ± 597 mg/kg within 2 months, and the relative abundances of Sphingobium and Pseudomonas in soil increased more than fivefold. This study not only established a system for the isolation and identification of indigenous degrading strains that could efficiently degrade pollutants in the isolated environment but also enabled the isolated degrading strains to have potential application prospects in the in situ bioremediation of PHs-contaminated soils.

Physiological and biochemical characterization and genome analysis of Rhodococcus qingshengii strain 7B capable of crude oil degradation and plant stimulation

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Strain 7B grows in the presence of up to 10% sodium chloride and degrades crude oil, oil sludge and individual hydrocarbons.

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Over 15 days of the experiment, the strain utilized 51% of oil at 28°C and 24% at 45°C.

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When colonizing the wheat root, the strain forms biofilms in the calyptrogen sheath and at the base of the root hairs.

Rhodococci are typical soil inhabitants which take part in remediation of soil polluted with hydrocarbons. In this paper, we describe a new strain, Rhodococcus qingshengii 7B, which is capable of growth and hydrocarbon degradation at 45°C and in the presence of up to 10% NaCl in the medium. The genome of the 7B strain consists of a 6,278,280 bp chromosome and two plasmids. The circular plasmid is 103,992 bp in length. The linear plasmid is 416,450 bp in length. Genome analysis revealed the genes of degradation of various hydrocarbons, resistance to salt stress and plant growth promoting activity. This strain is promising for use in remediation of oil-contaminated soils, because it has a pronounced ability to utilize crude oil, oil sludge and individual hydrocarbons in a wide temperature range. Over 15 days of the experiment, the strain utilized 51% of crude oil at 28°C and 24% at 45 °С.

Mitigation and Remediation Technologies of Waxy Crude Oils’ Deposition within Transportation Pipelines: A Review

Deposition of wax is considered one of the most significant culprits in transporting petroleum crude oils, particularly at low temperatures. When lowering pressure and temperature during the flow of crude oil, the micelle structure of the crude oil is destabilized, allowing oil viscosity to increase and precipitating paraffin (wax) in the well tubulars and pipeline, which increase the complexity of this culprit. These deposited substances can lead to the plugging of production and flow lines, causing a decline in oil production and, subsequently, bulk economic risks for the oil companies. Hence, various approaches have been commercially employed to prevent or remediate wax deposition. However, further research is still going on to develop more efficient techniques. These techniques can be categorized into chemical, physical, and biological ones and hybridized or combined techniques that apply one or more of these techniques. This review focused on all these technologies and the advantages and disadvantages of these technologies.

Extremophilic Microorganisms for the Treatment of Toxic Pollutants in the Environment

As concerns about the substantial effect of various hazardous toxic pollutants on the environment and public health are increasing, the development of effective and sustainable treatment methods is urgently needed. In particular, the remediation of toxic components such as radioactive waste, toxic heavy metals, and other harmful substances under extreme conditions is quite difficult due to their restricted accessibility. Thus, novel treatment methods for the removal of toxic pollutants using extremophilic microorganisms that can thrive under extreme conditions have been investigated during the past several decades. In this review, recent trends in bioremediation using extremophilic microorganisms and related approaches to develop them are reviewed, with relevant examples and perspectives.

Microbial Biodegradation of Paraffin Wax in Malaysian Crude Oil Mediated by Degradative Enzymes

The deposition of paraffin wax in crude oil is a problem faced by the oil and gas industry during extraction, transportation, and refining of crude oil. Most of the commercialized chemical additives to prevent wax are expensive and toxic. As an environmentally friendly alternative, this study aims to find a novel thermophilic bacterial strain capable of degrading paraffin wax in crude oil to control wax deposition. To achieve this, the biodegradation of crude oil paraffin wax by 11 bacteria isolated from seawater and oil-contaminated soil samples was investigated at 70°C. The bacteria were identified as Geobacillus kaustophilus N3A7, NFA23, DFY1, Geobacillus jurassicus MK7, Geobacillus thermocatenulatus T7, Parageobacillus caldoxylosilyticus DFY3 and AZ72, Anoxybacillus geothermalis D9, Geobacillus stearothermophilus SA36, AD11, and AD24. The GCMS analysis showed that strains N3A7, MK7, DFY1, AD11, and AD24 achieved more than 70% biodegradation efficiency of crude oil in a short period (3 days). Notably, most of the strains could completely degrade C₃₇–C₄₀ and increase the ratio of C₁₄–C₁₈, especially during the initial 2 days incubation. In addition, the degradation of crude oil also resulted in changes in the pH of the medium. The degradation of crude oil is associated with the production of degradative enzymes such as alkane monooxygenase, alcohol dehydrogenase, lipase, and esterase. Among the 11 strains, the highest activities of alkane monooxygenase were recorded in strain AD24. A comparatively higher overall alcohol dehydrogenase, lipase, and esterase activities were observed in strains N3A7, MK7, DFY1, AD11, and AD24. Thus, there is a potential to use these strains in oil reservoirs, crude oil processing, and recovery to control wax deposition. Their ability to withstand high temperature and produce degradative enzymes for long-chain hydrocarbon degradation led to an increase in the short-chain hydrocarbon ratio, and subsequently, improving the quality of the oil.

Dynamic Experimental Study on the Paraffin Deposition Prevention Performance of Tungsten Alloy Coating Pipe in Simulating Vertical Wellbore

In this study, a self-designed apparatus was used to provide a quantitative evaluation of the wax prevention effect of tungsten alloy-coated tubing compared with ordinary tubing in oil production. The paraffin deposition of both pipes at different temperatures and different flow rates was studied. The efficiency of paraffin deposition prevention of the tungsten alloy coating pipe was analyzed. The results show that using this apparatus can efficiently and accurately calculate the wax prevention rate and can accurately obtain the wax deposit and wax thickness of the inner wall. The paraffin deposition of both pipes reaches the highest point at 290.15 K, and it reduces with the increase of flow rate. The use of the tungsten alloy coating pipe results in about 30% reduction in paraffin deposition. It provides a promising method for the paraffin inhibition to extend the wax removal cycle.

Newly Isolated Alkane Hydroxylase and Lipase Producing Geobacillus and Anoxybacillus Species Involved in Crude Oil Degradation

Isolation and studies of novel, crude oil biodegrading thermophilic strains may provide a wider knowledge in understanding their role in petroleum degradation. In this study, the screening of ten new thermophilic strains revealed that all strains were alkane hydroxylase producers and seven of them produced lipase concurrently. Three best strains were characterized and identified through 16S rRNA sequence analysis as Geobacillus sp. D4, Geobacillus sp. D7, and Anoxybacillus geothermalis D9 with GenBank accession numbers MK615934.1, MK615935.1, and MK615936.1, respectively. Gas chromatography (GC) analysis showed that all three strains were able to breakdown various compounds in crude oil such as alkanes, toxic poly-aromatic hydrocarbons (PAHs), organosulfur, carboxylic acids, alkene, resins, organosilicon, alcohol, organochlorine, and ester. For the first time, alkane hydroxylase and lipase activity as well as crude oil degradation by A. geothermalis species were reported. Geobacillus sp. D7 is the best alkane degrader followed by A. geothermalis D9 and Geobacillus sp. D4 with 17.3%, 13.1%, and 12.1% biodegradation efficiency (BE%), respectively. The potential of thermophiles isolated can be explored further for bioremediation of sites polluted by petroleum and oil spills.

Lead soaps formation and biodiversity in a XVIII Century wax seal coloured with minium

A multidisciplinary approach was carried out in order to study the biodeterioration and the associated microbiome of a XVIII Century wax seal coloured with minium. A small wax seal fragment was observed by scanning electron microscopy combined with energy dispersive spectroscopy in non-destructive mode. The same object was analysed by Raman and Fourier-transform infrared spectroscopy. The identification of the microbiota growing on the seal was performed with both a culture-dependent strategy, combined with hydrolytic assays, and high-throughput sequencing using the MinION platform. The whole bacterial 16S rRNA gene and the fungal markers ITS and 28S rRNA were targeted. It was observed that the carnauba wax coloured with lead tetroxide (minium) was covered by a biofilm consisting of a network of filaments and other structures of microbial origin. The culture-dependent and culture-independent investigations showed the presence of a complex microbiota composed mainly by fungal members, which demonstrated interesting properties related to lipids and lead processing. The formation of lead soaps and secondary biogenic minerals was also described.

Phenotypic Adaptations Help Rhodococcus erythropolis Cells during the Degradation of Paraffin Wax

During crude oil extraction, the reduction in temperature and pressure results in the precipitation of paraffin wax that contains 20-40 carbon chain hydrocarbons. The paraffin wax may accumulate inside production tubes, pipelines, and processing facilities, and also in tankers during petroleum transportation. There are few bacterial strains that are able to degrade solid substrates. In the present study, the biodegradation of paraffin is evaluated using Rhodococcus erythropolis cells. This bacterium is able to grow using paraffin wax from an oil refinery plant as the sole carbon source. The cells grow as a thick biofilm over the solid substrate, make scale-like structures that increase the area of the initially smooth surface of paraffin, produce biosurfactants, and become more negatively charged than ethanol- or glucose-grown cells. When paraffin wax is supplied as microparticles, to increase the cell-substrate contact area and to simulate paraffin precipitation, the cells also adjust the composition of the fatty acids of the phospholipids of the cellular membrane to decrease its fluidity and paraffin biodegradation increases considerably. The study suggests that the phenotypic adaptation of R. erythropolis cells may be used to degrade paraffin wax under real conditions.

Peculiarities and biotechnological potential of environmental adaptation by Geobacillus species

The genus Geobacillus comprises thermophilic bacilli capable of endospore formation. The members of this genus provide thermostable proteins and can be used in whole cell applications at elevated temperatures; therefore, these organisms are of biotechnological importance. While these applications have been described in previous reviews, the present paper highlights the environmental adaptations and genome diversifications of Geobacillus spp. and their applications in evolutionary-protein engineering. Despite their obligate thermophilic properties, Geobacillus spp. are widely distributed in nature. Because several isolates demonstrate remarkable properties for cell reproduction in their respective niches, they seem to exist not only as endospores but also as vegetative cells in diverse environments. This suggests their excellence in environmental adaptation via genome diversification; in fact, evidence suggests that Geobacillus spp. were derived from Bacillus spp. while diversifying their genomes via horizontal gene transfer. Moreover, when subjected to an environmental stressor, Geobacillus spp. diversify their genomes using inductive mutations and transposable elements to produce derivative cells that are adaptive to the stressor. Notably, inductive mutations in Geobacillus spp. occur more rapidly and frequently than the stress-induced mutagenesis observed in other microorganisms. Owing to this, Geobacillus spp. can efficiently generate mutant genes coding for thermostable enzyme variants from the thermolabile enzyme genes under appropriate selection pressures. This phenomenon provides a new approach to generate thermostable enzymes, termed as thermoadaptation-directed enzyme evolution, thereby expanding the biotechnological potentials of Geobacillus spp. In this review, we have discussed this approach using successful examples and major challenges yet to be addressed.

Methanogenic Paraffin Biodegradation: Alkylsuccinate Synthase Gene Quantification and Dicarboxylic Acid Production

Paraffinic n-alkanes (>C17) that are solid at ambient temperature comprise a large fraction of many crude oils. The comparatively low water solubility and reactivity of these long-chain alkanes can lead to their persistence in the environment following fuel spills and pose serious problems for crude oil recovery operations by clogging oil production wells. However, the degradation of waxy paraffins under the anoxic conditions characterizing contaminated groundwater environments and deep subsurface energy reservoirs is poorly understood. Here, we assessed the ability of a methanogenic culture enriched from freshwater fuel-contaminated aquifer sediments to biodegrade the model paraffin n-octacosane (C28H58). Compared with that in controls, the consumption of n-octacosane was coupled to methane production, demonstrating its biodegradation under these conditions. Smithella was postulated to be an important C28H58 degrader in the culture on the basis of its high relative abundance as determined by 16S rRNA gene sequencing. An identified assA gene (known to encode the α subunit of alkylsuccinate synthase) aligned most closely with those from other Smithella organisms. Quantitative PCR (qPCR) and reverse transcription qPCR assays for assA demonstrated significant increases in the abundance and expression of this gene in C28H58-degrading cultures compared with that in controls, suggesting n-octacosane activation by fumarate addition. A metabolite analysis revealed the presence of several long-chain α,ω-dicarboxylic acids only in the C28H58-degrading cultures, a novel observation providing clues as to how methanogenic consortia access waxy hydrocarbons. The results of this study broaden our understanding of how waxy paraffins can be biodegraded in anoxic environments with an application toward bioremediation and improved oil recovery.IMPORTANCE Understanding the methanogenic biodegradation of different classes of hydrocarbons has important applications for effective fuel-contaminated site remediation and for improved recovery from oil reservoirs. Previous studies have clearly demonstrated that short-chain alkanes (C17) that comprise many fuel mixtures. Using an enrichment culture derived from a freshwater fuel-contaminated site, we demonstrate that the model waxy alkane n-octacosane can be biodegraded under methanogenic conditions by a presumed Smithella phylotype. Compared with that of controls, we show an increased abundance and expression of the assA gene, which is known to be important for anaerobic n-alkane metabolism. Metabolite analyses revealed the presence of a range of α,ω-dicarboxylic acids found only in n-octacosane-degrading cultures, a novel finding that lends insight as to how anaerobic communities may access waxes as growth substrates in anoxic environments.

Enzyme-mediated biodegradation of long-chain n-alkanes (C32 and C40) by thermophilic bacteria

Removal of long-chain hydrocarbons and n-alkanes from oil-contaminated environments are mere important to reduce the ecological damages, while bio-augmentation is a very promising technology that requires highly efficient microbes. In present study, the efficiency of pure isolates, i.e., Geobacillus thermoparaffinivorans IR2, Geobacillus stearothermophillus IR4 and Bacillus licheniformis MN6 and mixed consortium on degradation of long-chain n-alkanes C₃₂ and C₄₀ was investigated by batch cultivation test. Biodegradation efficiencies were found high for C₃₂ by mixed consortium (90%) than pure strains, while the pure strains were better in degradation of C₄₀ than mixed consortium (87%). In contrast, the maximum alkane hydroxylase activities (161 µmol mg^-1 protein) were recorded in mixed consortium system that had supplied with C₄₀ as sole carbon source. Also, the alcohol dehydrogenase (71 µmol mg^-1 protein) and lipase activity (57 µmol mg^-1 protein) were found high. Along with the enzyme activities, the hydrophobicity natures of the bacterial strains were found to determine the degradation efficiency of the hydrocarbons. Thus, the study suggested that the hydrophobicity of the bacteria is a critical parameter to understand the biodegradation of n-alkanes.

Bioremediation of synthetic fatliquors under microaerobic condition

Synthetic fatliquors are useful as a fatliquoring agent, flotation agent and emulsifying agent in a wide range of industrial applications such as leather, pharmacy and farm chemicals. These fatliquors remain recalcitrant to natural biota in existing treatment plants. In the present study, the isolated microaerophilic Serratia sp. HA1 strain CSMB3 is capable of utilizing structurally different fatliquors as the sole substrate for their growth under microaerobic conditions. Degradation of vegetable fatliquors was observed from 95 to 97% in terms of lipids, with the production of lipase at 72 h. Degradation of synthetic fatliquors was observed in terms of chemical oxygen demand from 85% to a minimum of 25%. It is in the order of sulfited/sulfated fatliquors > sulfochlorinated fatliquors > chlorinated fatliquors. A thin layer chromatography chromatogram confirmed the degradation of non polar fatliquor to polar compounds. Production of the red pigment prodigiosin in synthetic fatliquors enhanced the growth of the isolate. Fourier transform infrared spectroscopy (FTIR) confirmed the bioremediation of sulfochlorinated fatliquor into lipids and fatty acids and gas chromatography-mass spectrometry (GC-MS) results confirmed that alcohols and esters are the final end products. Thus the isolated strain CSMB3 may be used in the treatment of wastewaters containing vegetable and synthetic fatliquors.

Systematic investigations on the biodegradation and viscosity reduction of long chain hydrocarbons using Pseudomonas aeruginosa and Pseudomonas fluorescens

The use of microorganisms has been researched extensively for possible applications related to hydrocarbon degradation in the petroleum industry. However, attempts to improve the effect of microorganisms on the viscosity of hydrocarbons, which find potential use in the development of robust models for biodegradation, have been rarely documented. This study investigates the degradation of long chain hydrocarbons, such as hexadecane and eicosane using Pseudomonas fluorescens PMMD3 (P. fluorescens) and Pseudomonas aeruginosa CPCL (P. aeruginosa). P. aeruginosa used here is isolated from petroleum contaminated sediments and the P. fluorescens is from the coastal area, and both have hydrocarbon degrading genes. The degradation of hydrocarbons is studied using carbon profiling and reduction in viscosity pre- and post-degradation of hydrocarbons. The carbon profiling has been obtained using gas chromatography-mass spectroscopy (GC-MS), and Fourier transform infrared spectrometer (FTIR) results. GC-MS results have indicated an improved biodegradation of hydrocarbons by 77-93% in one day. The yield coefficients of biomass (YX/S) for P. aeruginosa and P. fluorescens using hexadecane as a carbon source are 1.35 and 0.81 g g(-1), and the corresponding values with eicosane are 0.84 and 0.88 g g(-1). The viscosity of hexadecane is reduced by the order of 53 and 47%, while that of eicosane was reduced by 53 and 65%, using P. aeruginosa and P. fluorescens, respectively. This study also presents information on the activity of enzymes responsible for the hydrocarbon degradation. Pseudomonas species have shown their use in potential applications for bioremediation, oil-spill treatment, and flow assurance. We believe that this study will also provide stringent tests for possible model development for the bioremediation of long chain paraffins suitable for oilfield applications.

Biodiesel derived waste glycerol as an economic substrate for biosurfactant production using indigenous Pseudomonas aeruginosa

Biodiesel plant waste glycerol as low-cost substrate for biosurfactant production.

Vacuum distillation residue upgrading by an indigenous Bacillus cereus

BACKGROUND

Biological processing of heavy fractions of crude oils offers less severe process conditions and higher selectivity for refining. Biochemical Processes are expected to be low demand energy processes and certainly ecofriendly.

RESULTS

A strain of biosurfactant producing bacterium was isolated from an oil contaminated soil at Tehran refinery distillation unit. Based on selected phenotypic and genotypic characteristic including morphology, biochemical proprety, and 16 SrRNA sequencing identified as a novel strain of Bacillus cereus (JQ178332). This bacterium endures a wide range of pH, salinity and temperature. This specific strain utilizes both paraffin and anthracene as samples of aliphatic and polycyclic aromatic hydrocarbons. The ability of this bacterium to acquire all its energy and chemical requirements from Vacuum Distillation Residue (VR), as a net sample of problematic hydrocarbons in refineries, was studied. SARA test ASTM D4124-01 revealed 65.5% decrease in asphaltenic, 22.1% in aliphatics and 30.3% in Aromatics content of the VR in MSM medium. Further results with 0.9% saline showed 55% decrease in asphaltene content and 2.1% Aromatics respectively.

CONCLUSION

Remarkable abilities of this microorganism propose its application in an ecofriendly technology to upgrade heavy crude oils.

Identification of metabolites from benzo[a]pyrene oxidation by ligninolytic enzymes of Polyporus sp. S133

The biodegradation of benzo[a]pyrene (BaP) by using Polyporus sp. S133, a white-rot fungus isolated from oil-contaminated soil was investigated. Approximately 73% of the initial concentration of BaP was degraded within 30 d of incubation. The isolation and characterization of 3 metabolites by thin layer chromatography, column chromatography, and UV-vis spectrophotometry in combination with gas chromatography-mass spectrometry, indicated that Polyporus sp. S133 transformed BaP to BaP-1,6-quinone. This quinone was further degraded in 2 ways. First, BaP-1,6-quinone was decarboxylated and oxidized to form coumarin, which was then hydroxylated to hydroxycoumarin, and finally to hydroxyphenyl acetic acid by addition of an epoxide group. Second, Polyporus sp. S133 converted BaP-1,6-quinone into a major product, 1-hydroxy-2-naphthoic acid. During degradation, free extracellular laccase was detected with reduced activity of lignin peroxidase, manganese-dependent peroxidase and 2,3-dioxygenase, suggesting that laccase and 1,2-dioxygenase might play an important role in the transformation of PAHs compounds.

Isolation of a thermophilic bacterium, Geobacillus sp. SH-1, capable of degrading aliphatic hydrocarbons and naphthalene simultaneously, and identification of its naphthalene degrading pathway

A thermophilic naphthalene- and aliphatic hydrocarbon-degrading bacterium SH-1 was isolated from a deep oil well and identified as Geobacillus sp. n-alkanes from C12 to C33 in crude oil and naphthalene were effectively degraded by strain SH-1, and this strain could readily utilize these compounds as its sole carbon and energy resources. During the degradation of naphthalene, strain SH-1 initiated its attack on naphthalene by a monooxygenation at its C-1 to give 1-naphthol and further monooxygenation at C-2 to produce 1,2-dihydroxynaphthalene. The ring of 1,2-dihydroxynaphthalene was cleaved to form trans-o-hydroxybenzylidenepyruvate. Subsequently, trans-o-hydroxybenzylidenepyruvate was transformed to (2E)-3-(2-hydroxyphenyl)prop-2-enal by losing a carboxyl group. Additionally, benzoic acid was identified as an intermediate in the naphthalene degradation pathway of this Geobacillus strain. This study highlights an important potential use of the thermophilic degradative strain SH-1 in the cleanup of environmental contamination by naphthalene and crude oil and presents a mechanism for naphthalene metabolism.

Effect of microbial treatment on the prevention and removal of paraffin deposits on stainless steel surfaces

In this study, biosurfactant-producing strain N2 and non-biosurfactant producing stain KB18 were used to investigate the effects of microbial treatment on the prevention and removal of paraffin deposits on stainless steel surfaces. Strain N2, with a biosurfactant production capacity, reduced the contact angle of stainless steel to 40.04°, and the corresponding adhesion work of aqueous phase was decreased by 26.5 mJ/m(2). By contrast, KB18 could only reduce the contact angle to 50.83°, with a corresponding 7.6 mJ/m(2) decrease in the aqueous phase work adhesion. The paraffin removal test showed that the paraffin removal efficiencies of strain N2 and KB18 were 79.0% and 61.2%, respectively. Interestingly, the N2 cells could attach on the surface of the oil droplets to inhibit droplets coalescence. These results indicate that biosurfactant-producing strains can alter the wettability of stainless steel and thus eliminate paraffin deposition.

Microbial Prevention of Wax Deposition in Crude Oil

Microorganisms were obtained by separation and purification experiment from waxy oil production wells in Daqing Oilfield. The paraffin removal strain was named for S1, and the biological surfactant strain was named for G1. Microscopic and morphological examinations showed strain S1 was to be Bacillus Subtilis and strain G1 was to be Bacillus Cereus. As an indicator of the degradation of paraffin, strain S1 and strain G1 were added in different proportions, the optimum proportion was 5:2. In this proportion the degradation rate of paraffin could reach to 64%, the prevention rate of paraffin could reach to 55%. By experiment after mixed bacteria group treatment, the viscosity of crude oil reduced from 36.9mPa•s to 27.8mPa•s, the reduction rate of viscosity was 24.7%, and the freezing point of crude oil reduced by 3.6°C, paraffinic hydrocarbons of crude oil were degraded.

Isolation, characterization of Rhodococcus sp. P14 capable of degrading high-molecular-weight polycyclic aromatic hydrocarbons and aliphatic hydrocarbons

Rhodococcus sp. P14 was isolated from crude oil-contaminated sediments. This strain was capable of utilizing three to five rings polycyclic aromatic hydrocarbons (PAHs) including phenanthrene (Phe), pyrene (Pyr), and benzo[a]pyrene (BaP) as a sole carbon and energy source. After cultivated with 50mg/L of each PAH, strain P14 removed 43% Phe, 34% Pyr and 30% BaP in 30 d. Four different hydroxyphenanthrene products derived from Phe by strain P14 (1,2,3,4-hydroxyphenanthrene) were detected using SPME-GC-MS. Strain P14 also was capable of degrading mineral oil with n-alkanes of C17 to C21 carbon chain length. Compared with glucose-grown cells, PAHs-grown cells had decreased contents of shorter-chain length fatty acids (≤ C16:0), increased contents of C18:0, Me-C19:0 and disappeared odd-number carbon chain fatty acids. The contents of unsaturated C19:1, Me-C19:0 increased and C18:0 decreased in mineral oil-grown cells. At the same time, the strain P14 tended to float when cultivated in mineral oil-supplemented liquid medium. The degradation capability of P14 to alkane and PAHs and its floating characteristics will be very helpful for future's application in oil-spill bioremediation.

Simultaneous hydrocarbon biodegradation and biosurfactant production by oilfield-selected bacteria

AIMS

To study the bacterial diversity associated with hydrocarbon biodegradation potentiality and biosurfactant production of Tunisian oilfields bacteria.

METHODS AND RESULTS

Eight Tunisian hydrocarbonoclastic oilfields bacteria have been isolated and selected for further characterization studies. Phylogenetic analysis revealed that three thermophilic strains belonged to the genera Geobacillus, Bacillus and Brevibacillus, and that five mesophilic strains belonged to the genera Pseudomonas, Lysinibacillus, Achromobacter and Halomonas. The bacterial strains were cultivated on crude oil as sole carbon and energy sources, in the presence of different NaCl concentrations (1, 5 and 10%, w/v), and at 37 or 55°C. The hydrocarbon biodegradation potential of each strain was quantified by GC-MS. Strain C450R, phylogenetically related to the species Pseudomonas aeruginosa, showed the maximum crude oil degradation potentiality. During the growth of strain C450R on crude oil (2%, v/v), the emulsifying activity (E24) and glycoside content increased and reached values of 77 and 1.33 g l(-1), respectively. In addition, the surface tension (ST) decreased from 68 to 35.1 mN m(-1), suggesting the production of a rhamnolipid biosurfactant. Crude biosurfactant had been partially purified and characterized. It showed interest stability against temperature and salinity increasing and important emulsifying activity against oils and hydrocarbons.

CONCLUSIONS

The results of this study showed the presence of diverse aerobic bacteria in Tunisian oilfields including mesophilic, thermophilic and halotolerant strains with interesting aliphatic hydrocarbon degradation potentiality, mainly for the most biosurfactant produced strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

It may be suggested that the bacterial isolates are suitable candidates for practical field application for effective in situ bioremediation of hydrocarbon-contaminated sites.

Modification of progesterone and testosterone by a food-borne thermophile Geobacillus kaustophilus

The present work was carried out to study structural modification of steroids by Geobacillus kaustophilus, a bacterial thermophile present in milk and the environment. Incubation of progesterone and testosterone with G. kaustophilus at 65 degrees C resulted in oxygenated steroid nuclei. The oxygenation of the steroid molecule was stereo specific. Seven metabolites of progesterone horizontal line 6beta/6alpha-hydroxytestosterone, 20-hydroxyprogesterone, 6beta-/6alpha-20-dihydroxyprogesterone, 5alpha-pregnane-3,6,20-trione, and 3beta-hydroxy-5alpha-pregnane-6,20-dione horizontal line were identified. Four compounds horizontal line namely, 66-/6--hydroxytestosterone and 6beta/6alpha-hydroxyandrostenedione horizontal line and androst-4-en-3,17-dione were identified as testosterone metabolites. This shows that G. kaustophilus is capable of modifying steroid nuclei at elevated temperatures. G. kaustophilus is a stable thermophile first isolated from milk. Our results show that endogenous steroids present in milk can be modified by G. kaustophilus, causing detrimental effect on human health.

Naphthalene metabolism in Nocardia otitidiscaviarum strain TSH1, a moderately thermophilic microorganism

The thermophilic bacterium Nocardia otitidiscaviarum strain TSH1, originally isolated in our laboratory from a petroindustrial wastewater contaminated soil in Iran, grows at 50 degrees C on a broad range of hydrocarbons. Transformation of naphthalene by strain TSH1 which is able to use this two ring-polycyclic aromatic hydrocarbon (PAH) as a sole source of carbon and energy was investigated. The metabolic pathway was elucidated by identifying metabolites, biotransformation studies and monitoring enzyme activities in cell-free extracts. The identification of metabolites suggests that strain TSH1 initiates its attack on naphthalene by dioxygenation at its C-1 and C-2 positions to give 1,2-dihydro-1,2-dihydroxynaphthalene. The intermediate 2-hydroxycinnamic acid, characteristic of the meta-cleavage of the resulting diol was identified in the acidic extract. Apart from typical metabolites of naphthalene degradation known from mesophiles, benzoic acid was identified as an intermediate for the naphthalene pathway of this Nocardia strain. Neither phthalic acid nor salicylic acid metabolites were detected in culture extracts. Enzymatic experiments with cell extract showed the catechol 1,2-dioxygenase activity while transformation of phthalic acid and protocatechuic acid was not observed. The results of enzyme activity assays and identification of benzoic acid in culture extract provide strong indications that further degradation goes through benzoate and beta-ketoadipate pathway. Our results indicate that naphthalene degradation by thermophilic N. otitidiscaviarum strain TSH1 differs from the known pathways found for the thermophilic Bacillus thermoleovorans Hamburg 2 and mesophilic bacteria.