In Situ Biosurfactant Production by Bacillus Strains Injected into a Limestone Petroleum Reservoir

Biosurfactant-mediated oil recovery may be an economic approach for recovery of significant amounts of oil entrapped in reservoirs, but evidence that biosurfactants can be produced in situ at concentrations needed to mobilize oil is lacking. We tested whether two Bacillus strains that produce lipopeptide biosurfactants can metabolize and produce their biosurfactants in an oil reservoir. Five wells that produce from the same Viola limestone formation were used. Two wells received an inoculum (a mixture of Bacillus strain RS-1 and Bacillus subtilis subsp. spizizenii NRRL B-23049) and nutrients (glucose, sodium nitrate, and trace metals), two wells received just nutrients, and one well received only formation water. Results showed in situ metabolism and biosurfactant production. The average concentration of lipopeptide biosurfactant in the produced fluids of the inoculated wells was about 90 mg/liter. This concentration is approximately nine times the minimum concentration required to mobilize entrapped oil from sandstone cores. Carbon dioxide, acetate, lactate, ethanol, and 2,3-butanediol were detected in the produced fluids of the inoculated wells. Only CO₂ and ethanol were detected in the produced fluids of the nutrient-only-treated wells. Microbiological and molecular data showed that the microorganisms injected into the formation were retrieved in the produced fluids of the inoculated wells. We provide essential data for modeling microbial oil recovery processes in situ, including growth rates (0.06 ± 0.01 h⁻¹), carbon balances (107% ± 34%), biosurfactant production rates (0.02 ± 0.001 h⁻¹), and biosurfactant yields (0.015 ± 0.001 mol biosurfactant/mol glucose). The data demonstrate the technical feasibility of microbial processes for oil recovery.     

Importance of 3-hydroxy fatty acid composition of lipopeptides for biosurfactant activity

Biosurfactant production may be an economic approach to improving oil recovery. To obtain candidates most suitable for oil recovery, 207 strains, mostly belonging to the genus Bacillus, were tested for growth and biosurfactant production in medium with 5% NaCl under aerobic and anaerobic conditions. All strains grew aerobically with 5% NaCl, and 147 strains produced a biosurfactant. Thirty-five strains grew anaerobically with 5% NaCl, and two produced a biosurfactant. In order to relate structural differences to activity, eight lipopeptide biosurfactants with different specific activities produced by various Bacillus species were purified by a new protocol. The amino acid compositions of the eight lipopeptides were the same (Glu/Gln:Asp/Asn:Val:Leu, 1:1:1:4), but the fatty acid compositions differed. Multiple regression analysis showed that the specific biosurfactant activity depended on the ratios of both iso to normal even-numbered fatty acids and anteiso to iso odd-numbered fatty acids. A multiple regression model accurately predicted the specific biosurfactant activities of four newly purified biosurfactants (r2= 0.91). The fatty acid composition of the biosurfactant produced by Bacillus subtilis subsp. subtilis strain T89-42 was altered by the addition of branched-chain amino acids to the growth medium. The specific activities of biosurfactants produced in cultures with different amino acid additions were accurately predicted by the multiple regression model derived from the fatty acid compositions (r2= 0.95). Our work shows that many strains of Bacillus mojavensis and Bacillus subtilis produce biosurfactants and that the fatty acid composition is important for biosurfactant activity.     

Basis for formulating biosurfactant mixtures to achieve ultra low interfacial tension values against hydrocarbons

Biosurfactants could potentially replace or be used in conjunction with synthetic surfactants to provide for more cost-effective subsurface remediation. The design of surfactant formulations that are effective in lowering interfacial tension (IFT), which is necessary to mobilize entrapped hydrocarbons, requires information about the surface-active agent (surfactant) and the targeted non-aqueous phase liquids (NAPL). We hypothesized that biosurfactant and synthetic surfactant mixtures can be formulated to provide the appropriate hydrophobic/hydrophilic conditions necessary to produce low IFT against NAPLs, and that such mixtures will produce synergism that make them more effective than individual biosurfactants or synthetic surfactants. Our work tested the interfacial activity of biosurfactants from individual strains and mixtures of biosurfactants from different strains with and without a synthetic surfactant. Multiple regression analysis showed that, for lipopeptide biosurfactants produced by various Bacillus species, the interfacial activity against toluene depended on the relative proportions of 3-OH-C₁₄, C₁₅, C₁₆, and C₁₈ in the fatty acid tail. As the fatty acid composition became more heterogeneous the system produced lower IFT against toluene. In mixtures of lipopeptide biosurfactants with the more hydrophilic, rhamnolipid biosurfactant, the IFT against toluene decreased as the percentage of the 3-OH C₁₄ fatty acid increased in the lipopeptide. Mixtures of lipopeptide biosurfactants with the more hydrophobic synthetic surfactant, C12, C13-8PO SO₄Na, were able to produce low IFT against hexane and decane. In general, we found that lipopeptide biosurfactants with a heterogeneous fatty acid composition or mixtures of lipopeptide and rhamnolipid biosurfactants lowered the IFT against hydrophilic NAPLs. Conversely, mixtures of lipopeptide biosurfactants with a more hydrophobic synthetic surfactant lowered the IFT against hydrophobic NAPLs.     

Importance of 3-Hydroxy Fatty Acid Composition of Lipopeptides for Biosurfactant Activity

Biosurfactant production may be an economic approach to improving oil recovery. To obtain candidates most suitable for oil recovery, 207 strains, mostly belonging to the genus Bacillus, were tested for growth and biosurfactant production in medium with 5% NaCl under aerobic and anaerobic conditions. All strains grew aerobically with 5% NaCl, and 147 strains produced a biosurfactant. Thirty-five strains grew anaerobically with 5% NaCl, and two produced a biosurfactant. In order to relate structural differences to activity, eight lipopeptide biosurfactants with different specific activities produced by various Bacillus species were purified by a new protocol. The amino acid compositions of the eight lipopeptides were the same (Glu/Gln:Asp/Asn:Val:Leu, 1:1:1:4), but the fatty acid compositions differed. Multiple regression analysis showed that the specific biosurfactant activity depended on the ratios of both iso to normal even-numbered fatty acids and anteiso to iso odd-numbered fatty acids. A multiple regression model accurately predicted the specific biosurfactant activities of four newly purified biosurfactants (r² = 0.91). The fatty acid composition of the biosurfactant produced by Bacillus subtilis subsp. subtilis strain T89-42 was altered by the addition of branched-chain amino acids to the growth medium. The specific activities of biosurfactants produced in cultures with different amino acid additions were accurately predicted by the multiple regression model derived from the fatty acid compositions (r² = 0.95). Our work shows that many strains of Bacillus mojavensis and Bacillus subtilis produce biosurfactants and that the fatty acid composition is important for biosurfactant activity.     

Bacterial biosurfactant increases ex situ biodiesel bioremediation in clayey soil

The contamination of soils by oily compounds has several environmental impacts, which can be reversed through bioremediation, using biosurfactants as auxiliaries in the biodegradation process. In this study, we aimed to perform ex situ bioremediation of biodiesel-contaminated soil using biosurfactants produced by Bacillus methylotrophicus. A crude biosurfactant was produced in a whey-based culture medium supplemented with nutrients and was later added to biodiesel-contaminated clayey soil. The produced lipopeptide biosurfactant could reduce the surface tension of the fermentation broth to 30.2 mN/m. An increase in the microbial population was observed in the contaminated soil; this finding can be corroborated by the finding of increased CO₂ release over days of bioremediation. Compared with natural attenuation, the addition of a lower concentration of the biosurfactant (0.5% w/w in relation to the mass of diesel oil) to the soil increased biodiesel removal by about 16% after 90 days. The added biosurfactant did not affect the retention of the contaminant in the soil, which is an important factor to be considered when applying in situ bioremediation technologies.

     

Biosurfactant-producing Bacillus are present in produced brines from Oklahoma oil reservoirs with a wide range of salinities

Nine wells producing from six different reservoirs with salinities ranging from 2.1% to 15.9% were surveyed for presence of surface-active compounds and biosurfactant-producing microbes. Degenerate primers were designed to detect the presence of the surfactin/lichenysin (srfA3/licA3) gene involved in lipopeptide biosurfactant production in members of Bacillus subtilis/licheniformis group and the rhlR gene involved in regulation of rhamnolipid production in pseudomonads. Polymerase chain reaction amplification, cloning, and sequencing confirmed the presence of the srfA3/licA3 genes in brines collected from all nine wells. The presence of B. subtilis/licheniformis strains was confirmed by sequencing two other genes commonly used for taxonomic identification of bacteria, gyrA (gyrase A) and the 16S rRNA gene. Neither rhlR nor 16S rRNA gene related to pseudomonads was detected in any of the brines. Intrinsic levels of surface-active compounds in brines were low or not detected, but biosurfactant production could be stimulated by nutrient addition. Supplementation with a known biosurfactant-producing Bacillus strain together with nutrients increased biosurfactant production. The genetic potential to produce lipopeptide biosurfactants (e.g., srfA3/licA3 gene) is prevalent, and nutrient addition stimulated biosurfactant production in brines from diverse reservoirs, suggesting that a biostimulation approach for biosurfactant-mediated oil recovery may be technically feasible.     

厌氧产脂肽工程菌的构建及其代谢活性评价

利用微生物产生生物表面活性剂驱油,是微生物采油的重要技术之一.但油藏的缺氧环境使得大多数生物表面活性剂产生菌的代谢活性受到限制.本研究以筛选自油田采出水中的好氧产脂肽类表面活性剂的解淀粉芽孢杆菌BQ-2和兼性厌氧的施氏假单胞菌DQ-1为亲本菌,通过原生质体融合的方法构建了一株能在厌氧条件下迅速生长并能产脂肽类表面活性剂的融合子JD-3.融合子JD-3的菌落形态与亲本菌株BQ-2相似,其16S rDNA序列与BQ-2的相似度达99%;在厌氧条件下培养36 h,融合子JD-3发酵液的表面张力由初始的63.0 mN·m^-1降至32.5 mN·m^-1;薄层层析及红外光谱分析结果显示,JD-3在厌氧条件下的产物为脂肽类表面活性剂;该表面活性剂的临界胶束浓度(CMC)为90 mg·L^-1,且对原油、液体石蜡、煤油等有较好的乳化活性.JD 3在厌氧条件下可以蔗糖、葡萄糖或甘油为碳源,以蛋白胨等为氮源合成脂肽类表面活性剂,且经多次厌氧传代培养仍保持稳定的产生物表面活性剂功能,显示该菌株在油藏厌氧条件下对提高原油采收率具有较好的应用潜力.     

Antimicrobial potential of a lipopeptide biosurfactant derived from a marine Bacillus circulans

Aims: To isolate the biologically active fraction of the lipopeptide biosurfactant produced by a marine Bacillus circulans and study its antimicrobial potentials. Methods and Results: The marine isolate B. circulans was cultivated in glucose mineral salts medium and the crude biosurfactant was isolated by chemical isolation method. The crude biosurfactants were solvent extracted with methanol and the methanol extract was subjected to reverse phase high‐performance liquid chromatography (HPLC). The crude biosurfactants resolved into six major fractions in HPLC. The sixth HPLC fraction eluting at a retention time of 27·3 min showed the maximum surface tension‐reducing property and reduced the surface tension of water from 72 mNm^?1 to 28 mNm^?1. Only this fraction was found to posses bioactivity and showed a pronounced antimicrobial action against a panel of Gram‐positive and Gram‐negative pathogenic and semi‐pathogenic micro‐organisms including a few multidrug‐resistant (MDR) pathogenic clinical isolates. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of this antimicrobial fraction of the biosurfactant were determined for these test organisms. The biosurfactant was found to be active against Gram‐negative bacteria such as Proteus vulgaris and Alcaligens faecalis at a concentration as low as 10 μg ml^?1. The biosurfactant was also active against methicillin‐resistant Staphylococcus aureus (MRSA) and other MDR pathogenic strains. The chemical identity of this bioactive biosurfactant fraction was determined by post chromatographic detection using thin layer chromatography (TLC) and also by Fourier transform infrared (FTIR) spectroscopy. The antimicrobial HPLC fraction resolved as a single spot on TLC and showed positive reaction with ninhydrin, iodine and rhodamine‐B reagents, indicating its lipopeptide nature. IR absorption by this fraction also showed similar and overlapping patterns with that of other lipopeptide biosurfactants such as surfactin and lichenysin, proving this biosurfactant fraction to be a lipopeptide. The biosurfactant did not show any haemolytic activity when tested on blood agar plates, unlike the lipopeptide biosurfactant surfactin produced by Bacillus subtilis. Conclusions: The biosurfactant produced by marine B. circulans had a potent antimicrobial activity against Gram‐positive and Gram‐negative pathogenic and semi‐pathogenic microbial strains including MDR strains. Only one of the HPLC fractions of the crude biosurfactants was responsible for its antimicrobial action. The antimicrobial lipopeptide biosurfactant fraction was also found to be nonhaemolytic in nature. Significance and impact of the study: This work presents a nonhaemolytic lipopeptide biosurfactant produced by a marine micro‐organism possessing a pronounced antimicrobial action against a wide range of bacteria. There is a high demand for new antimicrobial agents because of the increased resistance shown by pathogenic micro‐organisms against the existing antimicrobial drugs. This study provides an insight into the search of new bioactive molecules from marine micro‐organisms.     

Potential application of Bacillus subtilis SPB1 biosurfactants in laundry detergent formulations: Compatibility study with detergent ingredients and washing performance

Surfactants play a very important role in laundry and household cleaning products ingredients. In this research, the application of lipopeptide biosurfactants, produced by Bacillus subtilis SPB1, in the formulation of a washing powder was investigated. The SPB1 biosurfactant was mixed with sodium tripolyphosphate as a builder and sodium sulfate as filler. The efficiency of the formulated detergent composition with different washing conditions to remove a stain from cotton fabric was examined. The results showed that the formulated detergent was effective in oil removal, with optimal washing conditions of pH, temperature, striate and time of washing system of 7, 65°C, 1000 RPM and 60 min, respectively. A comparative study of different detergent compositions (biosurfactant‐based detergent, combined biosurfactant‐commercial detergent, and a commercial detergent) for the removal of oil and tea stains, proved that the bio‐scouring was more effective (>75%) in terms of the stain removal than the commercial powders (<60%). Moreover, the results demonstrated that the biosurfactant acts additively with a commercial detergent and enhances their performance from 33 to 45% in removing oil stain and from 57 to 64% in removing tea stain. As a conclusion, in addition to the low toxicity and the high biodegradability of the microbial biosurfactants, the results of this study have shown that the future use of this lipopeptide biosurfactant as laundry detergent additive is highly promising.     

Evaluation of bioemulsifier mediated Microbial Enhanced Oil Recovery using sand pack column

Bacillus licheniformis K125, isolated from an oil reservoir, produces an effective bioemulsifier. The crude bioemulsifier showed 66% emulsification activity (E(24)) and reduced the surface tension of water from 72 to 34 mN/m. It contains substantial amount of polysaccharide, protein and lipid. This bioemulsifier is pseudoplastic non-Newtonian in nature. It forms oil in water emulsion which remains stable at wide range of pH, temperature and salinity. It gave 43+/-3.3% additional oil recovery upon application to a sand pack column designed to simulate an oil reservoir. This is 13.7% higher than that obtained from crude lipopeptide biosurfactants produced by the standard strain, Bacillus mojavensis JF2 and 8.5% higher than hot water spring isolate, Bacillus licheniformis TT42. The increased oil recovery obtained by using the crude bioemulsifier can be attributed to its combined surface and emulsification activity. Its mechanism of oil recovery must be similar to the mechanism exhibited by surfactant-polymer flooding process of chemical enhanced oil recovery.     

Screening of biosurfactant-producing Bacillus strains using glycerol from the biodiesel synthesis as main carbon source

Glycerol, a co-product of biodiesel production, was evaluated as carbon source for biosurfactant production. For this reason, seven non-pathogenic biosurfactant-producing Bacillus strains, isolated from the tank of chlorination at the Wastewater Treatment Plant at Federal University of Ceara, were screened. The production of biosurfactant was verified by determining the surface tension value, as well as the emulsifying capacity of the free-cell broth against soy oil, kerosene and N-hexadecane. Best results were achieved when using LAMI005 and LAMI009 strains, whose biosurfactant reduced the surface tension of the broth to 28.8?±?0.0 and 27.1?±?0.1?mN?m(-1), respectively. Additionally, at 72?h of cultivation, 441.06 and 267.56?mg?L(-1) of surfactin were produced by LAMI005 and LAMI009, respectively. The biosurfactants were capable of forming stable emulsions with various hydrocarbons, such as soy oil and kerosene. Analyses carried out with high performance liquid chromatography (HPLC) showed that the biosurfactant produced by Bacillus subtilis LAMI009 and LAMI005 was compatible with the commercially available surfactin standard. The values of minimum surface tension and the CMC of the produced biosurfactant indicated that it is feasible to produce biosurfactants from a residual and renewable and low-cost carbon source, such as glycerol.     

Production and characterization of biosurfactants from Bacillus licheniformis F2.2

A biosurfactant-producing strain, Bacillus licheniformis F2.2, was isolated from a fermented food in Thailand. The strain was capable of producing a new biosurfactant, BL1193, as well as two kinds of popular lipopeptide biosurfactants, plipastatin and surfactin. Mass spectrometry and FT-IR analysis indicated that BL1193 had a molecular mass of 1,193 Da with no peptide portion in the molecule. While plipastatin and surfactin were abundantly produced in a nutrient YPD medium, BL1193 was produced only in a synthetic DF medium containing no amino acids. According to an oil displacement activity test, the specific activity of BL1193 (6.53 kBS units/mg) is equivalent to that of surfactin (5.78-6.83 kBS units/mg).     

The Effects of a Bacillus Biosurfactant on Methanogenic Hexadecane Degradation

The effects of microbially produced biosurfactants on hydrocarbon degradation have been examined previously by other researchers. However, almost all of these studies were conducted using rhamnolipid biosurfactants produced by various Pseudomonas species under aerobic conditions. The purpose of this study was to elucidate the effects of various levels of the Bacillus sp. JF2 lipopeptide biosurfactant on the degradation of hexadecane under methanogenic conditions. Hexadecane degradation did increase significantly when levels below critical micelle concentration of the pre-purified biosurfactant were added. However, at levels above this amount of biosurfactant, degradation of hexadecane appeared to be inhibited. The terminal electron accepting process, methanogenesis, was stimulated by surfactant addition. A review of the published literature revealed a wide variety of results, some which are similar to, but many that differ from those reported here. However, the results from this study were reproducible. Although there is no clear explanation for these results, more research on the effect of biosurfactants produced by Gram positive bacteria on the biodegradation of hydrocarbons is needed, as well as further studies under anaerobic conditions.     

The Effects of a Bacillus Biosurfactant on Methanogenic Hexadecane Degradation

The effects of microbially produced biosurfactants on hydrocarbon degradation have been examined previously by other researchers. However, almost all of these studies were conducted using rhamnolipid biosurfactants produced by various Pseudomonas species under aerobic conditions. The purpose of this study was to elucidate the effects of various levels of the Bacillus sp. JF2 lipopeptide biosurfactant on the degradation of hexadecane under methanogenic conditions. Hexadecane degradation did increase significantly when levels below critical micelle concentration of the pre-purified biosurfactant were added. However, at levels above this amount of biosurfactant, degradation of hexadecane appeared to be inhibited. The terminal electron accepting process, methanogenesis, was stimulated by surfactant addition. A review of the published literature revealed a wide variety of results, some which are similar to, but many that differ from those reported here. However, the results from this study were reproducible. Although there is no clear explanation for these results, more research on the effect of biosurfactants produced by Gram positive bacteria on the biodegradation of hydrocarbons is needed, as well as further studies under anaerobic conditions.     

Anti-adhesion activity of two biosurfactants produced by <Emphasis Type="Italic">Bacillus</Emphasis> spp. prevents biofilm formation of human bacterial pathogens

In this work, two biosurfactant-producing strains, Bacillus subtilis and Bacillus licheniformis, have been characterized. Both strains were able to grow at high salinity conditions and produce biosurfactants up to 10% NaCl. Both extracted-enriched biosurfactants showed good surface tension reduction of water, from 72 to 26–30 mN/m, low critical micelle concentration, and high resistance to pH and salinity. The potential of the two lipopeptide biosurfactants at inhibiting biofilm adhesion of pathogenic bacteria was demonstrated by using the MBEC device. The two biosurfactants showed interesting specific anti-adhesion activity being able to inhibit selectively biofilm formation of two pathogenic strains. In particular, Escherichia coli CFT073 and Staphylococcus aureus ATCC 29213 biofilm formation was decreased of 97% and 90%, respectively. The V9T14 biosurfactant active on the Gram-negative strain was ineffective against the Gram-positive and the opposite for the V19T21. This activity was observed either by coating the polystyrene surface or by adding the biosurfactant to the inoculum. Two fractions from each purified biosurfactant, obtained by flash chromatography, fractions (I) and (II), showed that fraction (II), belonging to fengycin-like family, was responsible for the anti-adhesion activity against biofilm of both strains.     

Detecting Surfactant-producing Microorganisms by the Drop-collapse Test

Summary A rapid method, ’drop-collapse’, was used for screening biosurfactant production by Pseudomonas aeruginosa, Bacillus subtilis, Candida albicans and Phanerochaete chrysosporium liquid cultures. Before measuring the total biosurfactant, the drop-collapse method was used in order to detect rhamnolipid presence in the culture broths. The method was performed in a microwell plate; the polystyrene platform with small wells. If the culture broth contained biosurfactant, the droplets of the broth in the oil-coated wells collapsed. If not, there was no change in the shape of the droplets. Pseudomonas aeruginosa and Bacillus subtilis culture supernatants showed spreading movement, meaning that they produced biosurfactants. However, Candida albicans and Phanerochaete chrysosporium supernatants remained beaded, meaning they did not produce any type of microbial surfactant.     

Substrate dependent production of extracellular biosurfactant by a marine bacterium

The potential of a marine microorganism to utilize different carbon substrates for the production of an extracellular biosurfactant was evaluated. Among the several carbon substrates tested for this purpose, production of the crude biosurfactant was found to be highest with glycerol (2.9+/-0.11 g L(-1)) followed by starch (2.5+/-0.11 g L(-1)), glucose (1.16+/-0.11 g L(-1)) and sucrose (0.94+/-0.07 g L(-1)). The crude biosurfactant obtained from glycerol, starch and sucrose media had significantly higher antimicrobial action than those obtained from glucose containing medium. RP-HPLC resolved the crude biosurfactants into several fractions one of which had significant antimicrobial action. The antimicrobial fraction was found in higher concentrations in biosurfactant obtained using glycerol, starch and sucrose as compared to the biosurfactants from glucose medium, thereby explaining higher antimicrobial activity. The carbon substrate was thus found to affect biosurfactant production both in a qualitative and quantitative manner.     

Rapid quantification of a microbial surfactant by a simple turbidometric method

Quantification of the biosurfactants produced by a variety of microorganisms is a time taking and difficult task due to the lack of rapid, efficient and accurate methods. This work presents a simple turbidometric method for quantification of crude biosurfactants based on their property to become insoluble at low pH values. Biosurfactants obtained from a Bacillus sp. using different carbon substrates showed a good linear correlation (R(2)>0.99) between biosurfactant concentrations and turbidity in the range of 1 to 10 g L(-1) of crude biosurfactants. The substrate specific equations (SSE) and generalized equations (GE) developed in this work effectively predicted the amount of crude biosurfactant produced in different sets of fermentation experiments validating the method. A similar linear correlation was also observed with biosurfactants obtained from two other strains, Bacillus circulans and Pseudomonas sp. This simple method may prove to be effective in fast, accurate and inexpensive quantification of crude biosurfactants produced by diverse bacteria.     

Bench-Scale Production of Biosurfactants and their Potential in Ex-Situ MEOR Application

The fermentative production of biosurfactants by five Bacillus strains in a bench-scale bioreactor and evaluation of biosurfactant-based enhanced oil recovery using sand pack columns were investigated. Adjusting the initial dissolved oxygen to 100% saturation, without any further control and with collection of foam and recycling of biomass, gave higher biosurfactant production. The microorganisms were able to produce biosurfactants, thus reducing the surface tension and interfacial tension to 28 mN/m and 5.8–0.5 mN/m, respectively, in less than 10 hours. The crude surfactant concentration of 0.08–1.1 g/L, and critical micelle concentration (CMC) values of 19.4–39 mg/L, corresponding to the biosurfactants produced by the different Bacillus strains, were observed. The efficiency of crude biosurfactant preparation obtained from Bacillus strains for enhanced oil recovery, by sand pack column studies, revealed it to vary from 30.22–34.19% of the water flood residual oil saturation. The results are indicative of the potential of the strains for the development of ex-situ, microbial-enhanced, oil recovery processes.     

厌氧产表面活性剂微生物提高原油采收率的研究进展

微生物强化采油(microbial enhanced oil recovery,MEOR)是近年来在国内外发展迅速的一项提高原油采收率技术。微生物在油藏中高效生产表面活性剂等驱油物质是微生物采油技术成功实施的关键之一。然而,油藏的缺/厌氧环境严重影响好氧表面活性剂产生菌在油藏原位的生存与代谢活性;油藏注空气会增加开采成本,且注入空气的作用时效和范围难以确定。因此,开发厌氧产表面活性剂菌种资源并强化其驱油效率对于提高原油采收率具有重要意义。本文综述了国内外近年来利用厌氧产表面活性剂微生物提高原油采收率的研究进展,简述了微生物厌氧产表面活性剂的相关驱油机理、菌种资源开发现状以及油藏原位驱油应用进展,并对当前的研究提出了一些思考。