Isolation and comparison of biosurfactants produced by Bacillus subtilis PT2 and Pseudomonas aeruginosa SP4 for microbial surfactant-enhanced oil recovery

Application of biosurfactants in enhanced oil recovery ex-situ: a review

With a growing focus on environmentally friendly solutions, biosurfactants derived from plants or microorganisms have gained attention for Enhanced Oil Recovery (EOR) applications. Biosurfactants offer several advantages over existing options, including biodegradability, low toxicity, availability of raw materials, resistance to harsh reservoir conditions, and improved water/oil interfacial tension reduction. Different organisms, such as bacteria, fungi, and plants, can produce these natural surfactants. Bacillus sp. and Pseudomonas sp. bacteria are extensively studied for their ability to produce biosurfactants using low-cost carbon and nitrogen sources, exhibiting excellent surface activity and low critical micellar concentration (CMC). Fungi, though less commonly used, can also produce biosurfactants, albeit with lower interfacial activity. Plant-derived natural surfactants find wide application in laboratory tests for EOR, despite having higher CMC. This review not only summarizes the current knowledge on biosurfactants but also offers a novel comparative analysis of those produced by bacteria, fungi, and plants, examining their CMC, surface tension, and interfacial tension properties. Additionally, it quantifies the number of publications on the use of biosurfactants for Microbial Enhanced Oil Recovery ex-situ (MEOR ex-situ) over the past 30 years and compares these with biosurfactants derived from plant sources. Our study is unique in its comparative approach and the quantification of literature on MEOR ex-situ. The findings reveal that biosurfactants produced by bacteria generally exhibit superior surface activity, even at lower concentrations, compared to those produced by plants or fungi. This new comparative perspective and thorough literature analysis highlight the distinctive contributions of this study. Overall, the use of biosurfactants for EOR represents a promising approach to cleaner energy production, with the potential to reduce environmental impact while improving oil recovery.

Characterization and treatment of oily sludge: A systematic review

Oily sludge is a prevalent hazardous waste generated in the petroleum industry, and effectively treating it remains a key challenge for the petroleum and petrochemical sectors. This paper provides an introduction to the origin, properties, and hazards of oil sludge while summarizing various treatment methods focused on reduction, recycling, and harmlessness. These methods include combustion, stabilization/solidification, oxidation and biodegradation techniques, solvent extraction, centrifugation, surfactant-enhanced oil recovery processes as well as freezing-thawing procedures. Additionally discussed are pyrolysis, microwave radiation applications along with electrokinetic method utilization for oily sludge treatment. Furthermore explored are ultrasonic radiation techniques and froth flotation approaches. These technologies have been thoroughly examined through discussions that analyze their process principles while considering influencing factors as well as advantages and disadvantages associated with each method. Based on the characteristics of oily sludge properties and treatment requirements, a selection methodology for choosing appropriate oily sludge treatment technology is proposed in this study. The development direction of processing technology has also been explored to provide guidance aimed at improving efficiency by optimizing existing processing technologies. The paper presents a comprehensive treatment method for oily sludge, ensuring that all the parameters meet the standard requirements.

Biosurfactant and biopolymer producing microorganisms from West Kazakhstan oilfield

Microbiological enhanced oil recovery (MEOR) uses indigenous or exogenous microorganisms and nutrients to enhance oil production through synthesis of metabolites reducing oil viscosity and surface tension. In order to find bacteria suitable for MEOR, we studied 26 isolates from wells in the Akingen oilfield in West Kazakhstan. Six of them were selected for further analysis based on their ability to reduce surface tension to less than 40 mN/m, with the A9 isolate exhibiting tension reduction values of 32.76 ± 0.3 mN/m. Based on the morphological features, biochemical activities, and the 16S rRNA gene, the isolates were classified to the Bacillus subtilis group. In the phylogenetic analysis the isolates grouped into two main clusters. Genes encoding the surfactin synthetase subunits were found in A2, A8, A9, A12, PW2, only the PW2 strain had lchAA encoding lichenysin, while sacB encoding levan was noted in A2, A8, A9, and A12. The expression of srfAB, srfAC, and sacB tested with qPCR varied among strains. Nevertheless, whereas temperature moderately affects the expression level, with the highest level recorded at 40 °C, salinity significantly impacts the expression of the genes encoding biosurfactants. B. subtilis strains isolated in the study, especially A9, are promising for microbial-enhanced oil recovery.

Valorization of oily sludge waste using biosurfactant-producing bacteria

Oily sludge generated by the petroleum industry is not only an environmental hazard, but since it contains crude oil too, it is a valuable resource as well. This study demonstrates a methodology for the valorization of the oily sludge that allows the recovery of oil fractions by the action of microbes producing surface-active metabolites. Two bacterial isolates were used in the study that were producing different biosurfactants, identified via FTIR analysis as well as through genomic mapping of the biosurfactant pathways using RAST, ANTISMASH 7.0, STRING databases. Serratia spp. AKBS12, produced a mono-rhamnolipid, while Acinetobacter spp. AKBS16, produced emulsan. Although recovery efficiency of both biosurfactants was similar, the recovery profile with respect to the class of hydrocarbons differed. The rhamnolipid produced by Serratia spp. AKBS12 extracted mono-chained paraffins and linear alkanes, while emulsan, produced by Acinetobacter spp. AKBS16 could extract heavier paraffins. The extraction procedure is simple and involves mixing the biosurfactant with oily sludge at a temperature of 30 °C with an incubation of 9 days. Sulphuric acid precipitation releases the oil trapped in the oily sludge. The study is the first step in developing user-friendly, innovative technologies that can be linked to the concept of a circular economy.

Microbial Lipopeptides: Properties, Mechanics and Engineering for Novel Lipopeptides

Microorganisms produce active surface agents called lipopeptides (LPs) which are amphiphilic in nature. They are cyclic or linear compounds and are predominantly isolated from Bacillus and Pseudomonas species. LPs show antimicrobial activity towards various plant pathogens and act by inhibiting the growth of these organisms. Several mechanisms are exhibited by LPs, such as cell membrane disruption, biofilm production, induced systematic resistance, improving plant growth, inhibition of spores, etc., making them suitable as biocontrol agents and highly advantageous for industrial utilization. The biosynthesis of lipopeptides involves large multimodular enzymes referred to as non-ribosomal peptide synthases. These enzymes unveil a broad range of engineering approaches through which lipopeptides can be overproduced and new LPs can be generated asserting high efficacy. Such approaches involve several synthetic biology systems and metabolic engineering techniques such as promotor engineering, enhanced precursor availability, condensation domain engineering, and adenylation domain engineering. Finally, this review provides an update of the applications of lipopeptides in various fields.

The release of petroleum hydrocarbons from a saline-sodic soil by the new biosurfactant-producing strain of Bacillus sp

Adsorption of old-aged petroleum hydrocarbons to the soil solid phase, which causes biosurfactant loss of performance, is among the limiting factors for the remediation of the saline-sodic soils contaminated with petroleum. Therefore, to find a functional biosurfactant in oil-contaminated saline-sodic soils, the efficiency of 39 bacteria isolated from petroleum-contaminated soils was evaluated. The strains were cultured in the Bushnell-Haas medium, and the produced biosurfactants and bioemulsifiers in this medium were extracted using chloroform/methanol and ethyl acetate extraction methods, respectively. Their partial purification was performed by column chromatography, and eventually, their performance in releasing TPH from the contaminated soil was evaluated. The soil test results revealed that the highest TPH releases due to the effects of the biosurfactants and bioemulsifier produced from SHA302, SH21, and SH72 isolates were 42.4% ± 0.2, 21.6% ± 0.15 and 24.3% ± 0.91, respectively. Based on the 16S rRNA gene sequence, the SHA302 strain showed 93.98% phylogenetic similarity with Bacillus pumilus strain ATCC 7061. The Fourier transform infrared spectroscopy and thin-layer chromatography results proved that the biosurfactants produced by isolates SHA302, SH21 and SH72 showed lipopeptide, glycolipoprotein and glycoprotein natures, respectively. The performance of the biosurfactant produced by SHA302 isolate indicated that it could be used as a good candidate for releasing TPH from saline-sodic soils with old contamination and facilitating the degradation of hydrocarbons.

Trend in Research on Characterization, Environmental Impacts and Treatment of Oily Sludge: A Systematic Review

Oily sludge is a hazardous material generated from the petroleum industry that has attracted increasing research interest. Although several review articles have dealt with specific subtopics focusing on the treatment of oily sludge based on selected references, no attempt has been made to demonstrate the research trend of oily sludge comprehensively and quantitatively. This study conducted a systematic review to analyze and evaluate all oily sludge-related journal articles retrieved from the Web of Science database. The results show that an increase in oily sludge-related research did not take place until recent years and the distribution of the researchers is geographically out of balance. Most oily sludge-related articles focused on treatment for harmfulness reduction or valorization with limited coverage of formation, characterization, and environmental impact assessment of oily sludge. Pyrolytic treatment has attracted increasing research attention in recent years. So far, the research findings have been largely based on laboratory-scale experiments with insufficient consideration of the cost-effectiveness of the proposed treatment methods. Although many methods have been proposed, few alone could satisfactorily achieve cost-effective treatment goals. To enable sustainable management of oily sludge on a global scale, efforts need to be made to fund more research projects, especially in the major oil-producing countries. Pilot-scale experiments using readily available and affordable materials should be encouraged for practical purposes. This will allow a sensible cost-benefit analysis of a proposed method/procedure for oily sludge treatment. To improve the treatment performance, combined methods are more desirable. To inform the smart selection of methods for the treatment of different oily sludge types, it is suggested to develop universally accepted evaluation systems for characterization and environmental risk of oily sludge.

Physicochemical Upgrading of a Biodetergent for Application in the Industrial Energy Sector

In the industries across the petroleum chain and those involved in energy generation, the use of petroderivatives as fuel oils is common. To clean parts, equipment and environments contaminated by hydrocarbons, they use expensive, toxic products, bringing risks to the environment as well as to workers’ health. Thus, the aim of this study was to check the stability of a biodetergent prepared using atoxic substances for large-scale production and industrial energy sector application. The relationship between volume (4 to 10 L) and stirring time (5 to 10 min) of the formulation at 3200 rpm and 80 °C was evaluated. The hydrophilic lipophilic balance (HLB), long-term stability (365 days), toxicity and efficiency of low-sulfur, viscous fuel oil removal from metal pieces and floors were investigated. The interaction among operating conditions was shown to influence the features of the product, which achieved approximately 100% stability after a stirring time of 7 min. The emulsion HBL index varied between 4.3 and 11.0. The biodetergent maintained its physicochemical properties during its 365 days of storage and showed high efficiency, removing 100% of the OCB1 impregnated on the metallic surfaces and floors tested. The formulation showed reliability in scale up when submitted to the study of physicochemical factors in the productive process, and safe application, by reducing risks for workers’ health and environment.

Nanobubbles activate anaerobic growth and metabolism of Pseudomonas aeruginosa

The effect of nanobubbles on anaerobic growth and metabolism of Pseudomonas aeruginosa was investigated. P. aeruginosa grew earlier in the culture medium containing nanobubbles and the bacterial cell concentration in that culture medium was increased a few times higher compared to the medium without nanobubbles under anaerobic condition. Both gas and protein, which are the metabolites of P. aeruginosa, were remarkably produced in the culture medium containing nanobubbles whereas those metabolites were little detected in the medium without nanobubbles, indicating nanobubbles activated anaerobic growth and metabolism of P. aeruginosa. The carbon dioxide nanobubbles came to be positively charged by adsorbing cations and delivered ferrous ions, one of the trace essential elements for bacterial growth, to the microbial cells, which activated the growth and metabolism of P. aeruginosa. The oxygen nanobubbles activated the activities of P. aeruginosa as an oxygen source.

Bioremediation of an agricultural saline soil contaminated with endosulfan and Escherichia coli by an active surface agent induced in a Penicillium crustosum culture

This study evaluates the production of a biological active surface agent (BASA) through its surface tension (ST) and emulsifying activity (E₂₄) for endosulfan degradation (ED) and Escherichia coli growth inhibition (EcGI) in an agricultural saline soil. The fungus, identified as Penicillium crustosum was isolated from the Citrus sinensis peel (CsP), then the surface properties were evaluated in 9 culture media through a Taguchi L9 experimental design. The culture conditions included: stirring speed, pH, carbon (C) and nitrogen (N) sources; being glucose, NH₄N0₃, 120 rpm and pH of 5, the most significant parameters in the BASA production. The BASA identified as a lipopeptide type, showed a ST = 38 mN m^-1 and E₂₄=71%. Both properties were stable at 80 °C, while ST presented stability in the pH range of 2 - 12, and a saline concentration of 200 g L^-1; E₂₄ was also stable at a pH between 8-12. Further application of BASA and fungal inoculum to a contaminated agricultural saline soil presented an EcGI of 99.8% on the 8th day, and ED of 92.9 ± 4.7% in 30 days, respectively; being the first report that uses this fungus for pesticide and bacteria elimination from an agricultural saline soil.

Kurstakin molecules facilitate diesel oil assimilation by Acinetobacter haemolyticus strain 2SA through overexpression of alkane hydroxylase genes

Biodegradation is a cost-effective process commonly used to eliminate many xenobiotic hydrocarbons such as diesel oils. However, their hydrophobic character reduces the biodegradation efficiency. In order to overcome this hurdle, kurstakins isolated from Bacillus thuringiensis strain 7SA were used as emulsifying agents. The influence of kurstakin molecules on diesel oil degradation by Acinetobacter haemolyticus strain 2SA was evaluated in the presence and absence of the aforementioned lipopeptide. The degradation rates and gene expressions of alkane hydroxylases were evaluated at days 4, 10, 14 and 21. Results showed that kurstakin molecules increased the hydrophobicity of 2SA. Moreover, diesel oil degradation activities were higher in the presence of kurstakin with 29%, 35%, 29% and 23% improvement at 4th, 10th, 14th and 21st day respectively. Statistical analysis indicated that the difference between the degradation rates in the presence and absence of kurstakin was significant with p = 0.03. The detection of three different hydroxylase genes namely alkB, almA and cyp153 in 2SA genome, might have allowed more efficient degradability of alkanes. According to the real-time PCR results, cyp153 was the most induced gene during diesel oil degradation in the presence and absence of kurstakin. Yet, the three genes demonstrated higher levels of expression in the presence of kurstakin when compared to its absence. This study showed that kurstakins enhance the diesel oil biodegradation rate by increasing the hydrophobicity of 2SA. In addition to their anti-fungal activities, kurstakins can be used as biosurfactant to increase biodegradation of diesel oil.

Effect of Fluid-Rock Interactions on In Situ Bacterial Alteration of Interfacial Properties and Wettability of CO2-Brine-Mineral Systems for Geologic Carbon Storage

This study explored the feasibility of biosurfactant amendment in modifying the interfacial characteristics of carbon dioxide (CO₂) with rock minerals under high-pressure conditions for GCS. In particular, while varying the CO₂ phase and the rock mineral, we quantitatively examined the production of biosurfactants by Bacillus subtilis and their effects on interfacial tension (IFT) and wettability in CO₂-brine-mineral systems. The results demonstrated that surfactin produced by B. subtilis caused the reduction of CO₂-brine IFT and modified the wettability of both quartz and calcite minerals to be more CO₂-wet. The production yield of surfactin was substantially greater with the calcite mineral than with the quartz mineral. The calcite played the role of a pH buffer, consistently maintaining the brine pH above 6. By contrast, an acidic condition in CO₂-brine-quartz systems caused the precipitation of surfactin, and hence surfactin lost its ability as a surface-active agent. Meanwhile, the CO₂-driven mineral dissolution and precipitation in CO₂-brine-calcite systems under a non-equilibrium system altered the solid substrates, produced surface roughness, and caused contact angle variations. These results provide unique experimental data on biosurfactant-mediated interfacial properties and wettability in GCS-relevant conditions, which support the exploitation of in situ biosurfactant production for biosurfactant-aided CO₂ injection.

Perylene pigment wastewater treatment by fenton-enhanced biological process

Polycyclic aromatic hydrocarbons (PAHs) are regarded as priority pollutants owing to their toxic, mutagenic and carcinogenic characteristics. Perylene is a kind of 5-ring PAH with biological toxicity, and classified as a class III carcinogen by the World Health Organization (WHO). Nowadays, some of its derivatives are often used as industrial pigments. Hence, urgent attention is highly needed to develop new and improved techniques for PAHs and their derivatives removal from the environment. In this study, Fenton oxidation process was hybridized with the biological (anaerobic and aerobic) treatments for the removal of perylene pigment from wastewater. The experiments were carried out by setting Fenton treatment system before and between the biological treatments. The biological results showed that COD removal efficiency reached 60% during 24 h HRT with an effluent COD concentration of 1567.78 mg/L. After the HRT increased to 48 h, the COD removal efficiency was slightly increased (67.9%). However, after combining Fenton treatment with biological treatment (Anaerobic-Fenton-Aerobic), the results revealed over 85% COD removal efficiency and the effluent concentration less than 600 mg/L which was selected as the better treatment configuration for the biological and chemical combined system. The microbial community analysis of activated sludge was carried out with high-throughput Illumina sequencing platform and results showed that Pseudomonas, Citrobacter and Methylocapsa were found to be the dominant genera detected in aerobic and anaerobic reactors. These dominant bacteria depicted that the community composition of the reactors for treating perylene pigments wastewater were similar to that of the soil contaminated by PAHs and the activated sludge from treating PAHs wastewater. Economic analysis results revealed that the reagent cost was relatively cheap, amounting to 10.64 yuan per kilogram COD. This study vividly demonstrated that combining Fenton treatment with biological treatment was efficient and cost-effective.

Swift production of rhamnolipid biosurfactant, biopolymer and synthesis of biosurfactant-wrapped silver nanoparticles and its enhanced oil recovery

Microbial enhanced oil recovery (MEOR) is a kind of enhanced oil recovery (EOR) development, often used as a tertiary stage where oil recovery is no longer possible utilizing primary and secondary conventional techniques. Among a few potential natural operators valuable for MEOR, biosurfactants, biopolymers and biosurfactant based nanoparticles assume key jobs. Biosurfactant which are produced by microorganisms’ act as are surface active agents that can be used as an alternative to chemically synthesized surfactants. Pseudomonas aeruginosa TEN01, a gram-negative bacterium isolated from the petroleum industry is a potential biosurfactant (Rhamnolipid) producer using cassava waste as the substrate. This work focuses on production and characterization of rhamnolipid from P. aeruginosa TEN01 and its use in enhanced oil recovery. The effectiveness of Chitosan that is deacetylated form of chitin which is a biopolymer that provides density and viscosity to the fluids is not known in enhanced oil recovery yet and so it is studied. Moreover, the fabrication of biosurfactant-mediated silver nanocrystals and its application in enhanced oil recovery is also studied. Sand-Pack column was constructed and the mechanism of oil recovery in the column was studied. While incubating the crude oil containing sand packed column with Biosurfactant-biopolymer and brine flooding in the ratio of 1:2, and Biosurfactant incubation - flooding with 3 g/l of biopolymer was found to be 34.28% and 44.5% respectively. The biosurfactant based silver nanoparticles are non-toxic and have better stability when compared to chemically synthesized silver nanoparticles. The oil recovery percentage by chemical based Ag NPs and biosurfactant based Ag NPs are 14.94% and 14.28% respectively.

Enhanced biodegradation of styrene vapors in the biotrickling filter inoculated with biosurfactant-generating bacteria under H2O2 stimulation

Biotrickling filters (BTFs) applied to hydrophobic volatile organic compounds (VOCs) suffer from limited mass transfer. Phase transfer kinetic and equilibrium effects limit the biodegradation of hydrophobic VOCs especially at high concentrations. This study evaluates two strategies for overcoming the problem. First, a natural process was used to enhance the aqueous availability of styrene, a hydrophobic VOC model, by inoculating the BTF with a mixture of biosurfactant-generating bacteria. This method achieved a maximum elimination capacity (ECmax) of 139 g m^-3h^-1 in the BTF at an empty bed residence time (EBRT) of 60s. The highest concentrations of the biosurfactants surfactin and rhamnolipid were 205 and 86 mg L^-1, respectively, in this step. Sequencing 16S rRNA confirmed the presence of biosurfactant-producing bacteria capable of biodegrading styrene in the BTF including Bacillus sonorensis, Bacillus subtilis, Lysinibacillus sphaericus, Lysinibacillus fusiformis, Alcaligenes feacalis, Arthrobacter creatinolyticus, and Kocuria rosea. Second, the effect of adding H₂O₂ to the recycle liquid on the BTF performance was determined. The biodegradation and mineralization of styrene in the BTF operated at a loading rate of 266 g m^-3h^-1 and H₂O₂/styrene molar ratio of 0.05 with EBRT as short as 15 s were 94% and 53%, respectively, with the EC of 250 g m^-3h^-1. High concentrations of antioxidant enzymes (peroxidase and catalase: 56 and 7 U g_biomass^-1, respectively) were produced and biosurfactant generation was increased in this step, contributing to enhanced styrene biodegradation and mineralization. The styrene biodegradation and mineralization values in the BTF in the last day operated under similar conditions but without H₂O₂ were 11.4% and 5.3%, respectively. The bacterial population had no considerable change in the BTF after adding H₂O₂. Accordingly, stimulating the BTF inoculated with biosurfactant-generating bacteria with H₂O₂ is a promising strategy for improving the biodegradation of hydrophobic VOCs.

Evaluation of a new strategy in the elaboration of culture media to produce surfactin from hemicellulosic corncob liquor

The biosurfactant production is characterized by high costs with substrates, which does not make them sufficiently competitive against synthetic surfactants. The insertion of alternative sources of low cost, especially agro-industrial residue, is an excellent alternative to make this competitiveness viable. An alkaline pretreatment was used to extract the hemicellulose from corncob in order to enhance its C5 fraction, common to vegetable biomasses. The hemicellulosic corncob liquor was used with glucose and mineral salt solution as carbon and nutrients sources in a fermentation process for the growth of Bacillus subtilis. It was performed a 2³ full factorial design to determine the best conditions for the surfactin production in relation to the following response variables: surface tension reduction rate (STRR) and emulsification index (EI₂₄), from which were obtained two optimized bioproducts under specific conditions. The optimized biosurfactants found to be effected presenting a critical micelle concentration of 100 mg.L^-1 and a maximum bioremediation potential of 85.18%, as well as maximum values of 57.38% and 65.30% for STRR and EI₂₄ variables, respectively. Overall results pointed for a successful commercial application for the surfactin produced.

Effect of biosurfactant derived from Vibrio natriegens MK3 against Vibrio harveyi biofilm and virulence

Vibrio harveyi is a marine luminous pathogen, which causes biofilm-mediated infections, pressures the search for an innovative alternate approach to strive against vibriosis in aquaculture. This study anticipated to explore the effect of glycolipid biosurfactant as an antipathogenic against V. harveyi to control vibriosis. In this study, 27 bacterial strains were isolated from marine soil sediments. Out of these, 11 strains exhibited surfactant activity and the strain MK3 showed high emulsification index. The potent strain was identified as Vibrio natriegens and named as V. natriegens MK3. The extracted biosurfactant was purified using high-performance liquid chromatography and it was efficient to decrease the surface tension of the growth medium up to 21 mN/m. The functional group and composition of the biosurfactant were determined by Fourier-transform infrared spectroscopy and nuclear magnetic resonance spectroscopy spectral studies and the nature of the biosurfactant was identified as glycolipid. The surfactant was capable of reducing the biofilm formation, bioluminescence, extracellular polysaccharide synthesis, and quorum sensing in marine shrimp pathogen V. harveyi. The antagonistic effect of biosurfactant was evaluated against V. harveyi-infected brine shrimp Artemia salina. This study reveals that biosurfactant can be considered for the management of biofilm-related aquatic infections.

Production and characterization of bioemulsifiers from Acinetobacter strains isolated from lipid-rich wastewater

In this study, two indigenous bacterial strains (Ab9-ES and Ab33-ES) isolated from lipid-rich wastewater showed potential to produce bioemulsifier in the presence of 2% (v/v) olive oil as a carbon source. These bacterial strains were identified as Acinetobacter sp. Ab9-ES and Acinetobacter sp. Ab33-ES by polymerase chain reaction and analysis of 16S rRNA gene sequences. Bioemulsifier production by these strains was found to be growth-linked. Maximum emulsifying activities (83.8% and 80.8%) were recorded from strains Ab9-ES and Ab33-ES, respectively. Bioemulsifier yields of 4.52 g/L and 4.31 g/L were obtained from strains Ab9-ES (XB9) and Ab33-ES (YB33), respectively. Fourier-transform infrared spectroscopic analysis revealed the glycoprotein nature of the bioemulsifiers. The bioemulsifiers formed stable emulsions only in the presence of edible oils. Maximum emulsifying activities of 79.6% (XB9) and 67.9% (YB33) were recorded in the presence of sunflower oil. The bioemulsifiers were found to be stable at a broad range of temperature (4-121 °C), moderate pH (5.0-10.0) and salinity (1-6%). In addition, bioemulsifier XB9 showed maximum emulsifying activities (77.3%, 74.5%, and 74.9%) at optimum temperature (50 °C), pH (7.0), and NaCl concentration (3%), respectively. On the contrary, YB33 demonstrated highest activities (73.6%, 72%, and 61.2%) at optimum conditions of 70 °C, pH 7.0, and NaCl concentration of 5%, respectively. Findings from this study suggest the potential biotechnological applications of the bioemulsifiers, especially in the remediation of oil-polluted sites.

Biosurfactant-Producing Capability and Prediction of Functional Genes Potentially Beneficial to Microbial Enhanced Oil Recovery in Indigenous Bacterial Communities of an Onshore Oil Reservoir

Microbial enhanced oil recovery (MEOR) is a bio-based technology with economic and environmental benefits. The success of MEOR depends greatly on the types and characteristics of indigenous microbes. The aim of this study was to evaluate the feasibility of applying MEOR at Mae Soon Reservoir, an onshore oil reservoir experiencing a decline in its production rate. We investigated the capability of the reservoir's bacteria to produce biosurfactants, and evaluated the potentials of uncultured indigenous bacteria to support MEOR by means of prediction of MEOR-related functional genes, based on a set of metagenomic 16s rRNA gene data. The biosurfactant-producing bacteria isolated from the oil-bearing sandstones from the reservoir belonged to one species: Bacillus licheniformis, with one having the ability to decrease surface tension from 72 to 32 mN/m. Gene sequences responsible for biosurfactant (licA3), lipase (lipP1) and catechol 2,3-dioxygenase (C23O) were detected in these isolates. The latter two, and other genes encoding MEOR-related functional proteins such as enoyl-CoA hydratase and alkane 1-monooxygenase, were predicted in the bacterial communities residing the reservoir's sandstones. Exposure of these sandstones to nutrients, consisting of KNO₃ and NaH₂PO₄, resulted in an increase in the proportions of some predicted functional genes. These results indicated the potentials of MEOR application at Mae Soon site. Using the approaches demonstrated in this study would also assist evaluation of the feasibility of applying MEOR in oil reservoirs, which may be enhanced by an appropriate nutrient treatment.

Experimental Investigations of Behaviour of Biosurfactants in Brine Solutions Relevant to Hydrocarbon Reservoirs

In this study, we investigated the behaviour of rhamnolipid and Greenzyme in brine solutions relevant to hydrocarbon reservoir. Prior to this work, several studies only reported the behaviour of the biosurfactants dissolved in sodium chloride solutions of varied salinity. The results of this study are relevant to the application of the biosurfactants in enhanced oil recovery, during which the compounds are injected into reservoir saturated with formation water, typically of high salinity and complex composition. Surface tension and conductivity methods were used to determine the critical micelle concentrations of the biosurfactants, Gibbs surface excess concentrations and standard free energy at water-air interface. The results show that rhamnolipid and Greenzyme could reduce the surface tension of water from 72.1 ± 0.2 mN/m to 34.7 ± 0.4 mN/m and 47.1 ± 0.1 mN/m respectively. They were also found to be stable in high salinity and high temperature with rhamnolipid being sensitive to brine salinity, composition and pH while Greenzyme showed tolerance for high salinity. Furthermore, the Gibbs standard free energy of micellisation shows that rhamnolipid and Greenzyme have the tendency to spontaneously form micelles with rhamnolipid showing more surface adsorption. However from maximal Gibbs surface excess concentration calculations, Greenzyme monomers tend to favour aggregation more than that of rhamnolipid.

Maximisation of oil recovery from an oil-water separator sludge: Influence of type, concentration, and application ratio of surfactants

Worldwide the generation of oil sludges is approximately 160 million metric tonnes per annum. The washing of oil sludge with surfactant solutions can be used to recover the oil and reused as a feedstock for fuel production. There is a need to establish the influence of the surfactant type, concentration, and application (surfactant to oil sludge, S/OS) ratio to oil sludge for the maximisation of oil recovery. This study presented the oil recovery rates from the washing of an oil-water separator sludge using surfactants, Triton X-100, sodium dodecyl sulphate (SDS), Tween 80, rhamnolipid, and Triton X-114. The surfactants were characterised by critical micelle concentration (CMC), micelle size, and surface activity. A Taguchi experimental design was applied to reduce the number of experimental runs. In general, Triton X-100 and X-114, and rhamnolipid had higher micelle sizes and surfactant activities which resulted in higher oil recoveries. The key role of the surfactants in the washing was evidenced because the ORR values with the surfactants were significantly higher than the value with the control with no surfactant solution. The S/OS ratio was the factor with the largest effect on the Taguchi signal-to-noise ratio (an indicator of variation) of the oil recovery rate. The levels with the maximum recovery rate were 1:1 S/OS, 2CMC of surfactant concentration and Triton X-100 (32% ± 5), Triton X-114 (30% ± 7), and rhamnolipid (29% ± 8). In conclusion, less surfactant solution (1:1 S/OS) and low surfactant concentration (≤2CMC) provided the maximum oil recovery from this type of oil sludge. To our knowledge, no previous study with surfactants has reported low oil recovery values at high S/OS ratios in the oil sludge washing.

Partial characterization of a biosurfactant extracted from Pseudomonas sp. B0406 that enhances the solubility of pesticides

Biodegradation of some organochlorine and organophosphate pesticides is difficult because of their low solubility in water and, therefore, their low bioavailability. To overcome the hydrophobicity problem and the limited pesticide availability, biosurfactants play a major role. In this study, we evaluated the effect of an extract from Pseudomonas sp. B0406 strain with surfactant properties, on the solubility of two pesticides: endosulfan (ED) and methyl parathion (MP). Such a process was performed in order to increase the aqueous solubility of both pesticides, to increase its availability to microorganisms and to promote their biodegradation. The extract from Pseudomonas sp. B0406 showed a critical micellar concentration of 1.4 g/L and the surface tension at that point was 40.4 mN/m. The preliminary chemical and physical partial characterization of the extract with surfactant properties indicated that it is an anionic glycolipid, which increases the solubility of both pesticides of 0.41 at 0.92 mg/L for ED and of 34.58 at 48.10 mg/L for MP. The results of this study suggest the effectiveness of this extract in improving the solubility of both pesticides ED and MP in water and, therefore, of its potential use to enhance the degradation of these pesticides.

Optimization and characterization of biosurfactant production from kitchen waste oil using Pseudomonas aeruginosa

Kitchen waste oil (KWO) from catering industries or households was used as a low-cost carbon source for producing biosurfactants by self-isolated Pseudomonas aeruginosa. Fermentation performance with KWO was superior to those with four other carbon sources, with higher optical density (OD₆₀₀) of 2.33 and lower interfacial tension of 0.57 mN/m. Culture conditions for biosurfactant production were optimized, with optimal pH of 8.0 and nitrogen source concentration of 2.0 g/L, respectively. The results of infrared spectroscopy and liquid chromatography-mass spectrometry (LC-MS) showed that the biosurfactant was a mixture of six rhamnolipid congeners, among which Rha-Rha-C₁₀-C₁₀ and Rha-C₁₀-C₁₀ were the main components, with mass fraction of approximately 34.20 and 50.86%, respectively. The critical micelle concentration (CMC) obtained was 55.87 mg/L. In addition, the rhamnolipids exhibited excellent tolerance to temperature (20-100 °C), pH (6.0-12.0), and salinity (2-20%; w/v) in a wide range, thereby showing good stability to extreme environmental conditions. The rhamnolipids positively affected oil removal from oil sludge and KWO-contaminated cotton cloth, with removal rate of 34.13 and of 30.92%, respectively. Our results demonstrated that biosurfactant production from KWO was promising, with advantages of good performance, low cost and environmental safety.

Toward high-efficiency production of biosurfactant rhamnolipids using sequential fed-batch fermentation based on a fill-and-draw strategy

Rhamnolipids are the most promising biosurfactants, have widespread applications in many fields. However, low yield and productivity in fermentation caused a high production cost and thus prohibited the bulk applications of rhamnolipids in industry. In this study, a sequential fed-batch fermentation process with fill-and-draw operation was developed to improve rhamnolipids production. By utilizing this strategy, the total produced rhamnolipids reached over 150g/L, had a 163% and 102% increase over the traditional batch and fed-batch processes, respectively. This remarkable high production efficiency was achieved by the well-maintained high productivity of 0.4g/Lh for a period of 17 d. Astonishingly, the conversion yield was high as 84%, while this value was only 53.2% and 42.7% in the traditional batch and fed-batch process, respectively. The high-efficiency rhamnolipids production in this sequential fed-batch fermentation could be largely explained by a high presence of cell coupled with the replenishment of nutrients and dilution of toxic byproducts via fill-and-draw operation. In all, this validated fermentation strategy offers a great prospect for high-efficiency production of rhamnolipids in industry.

Increased Biological Activity of Aneurinibacillus migulanus Strains Correlates with the Production of New Gramicidin Secondary Metabolites

The soil-borne gram-positive bacteria Aneurinibacillus migulanus strain Nagano shows considerable potential as a biocontrol agent against plant diseases. In contrast, A. migulanus NCTC 7096 proved less effective for inhibition of plant pathogens. Nagano strain exerts biocontrol activity against some gram-positive and gram-negative bacteria, fungi and oomycetes through the production of gramicidin S (GS). Apart from the antibiotic effects, GS increases the rate of evaporation from the plant surface, reducing periods of surface wetness and thereby indirectly inhibiting spore germination. To elucidate the molecular basis of differential biocontrol abilities of Nagano and NCTC 7096, we compared GS production and biosurfactant secretion in addition to genome mining of the genomes. Our results proved that: (i) Using oil spreading, blood agar lysis, surface tension and tomato leaves wetness assays, Nagano showed increased biosurfactant secretion in comparison with NCTC 7096, (ii) Genome mining indicated the presence of GS genes in both Nagano and NCTC 7096 with two amino acid units difference between the strains: T342I and P419S. Using 3D models and the DUET server, T342I and P419S were predicted to decrease the stability of the NCTC 7096 GS synthase, (iii) Nagano produced two additional GS-like molecules GS-1155 (molecular weight 1155) and GS-1169 (molecular weight 1169), where one or two ornithine residues replace lysine in the peptide. There was also a negative correlation between surface tension and the quantity of GS-1169 present in Nagano, and (iv) the Nagano genome had a full protein network of exopolysaccharide biosynthesis in contrast to NCTC 7096 which lacked the first enzyme of the network. NCTC 7096 is unable to form biofilms as observed for Nagano. Different molecular layers, mainly gramicidin secondary metabolite production, account for differential biocontrol abilities of Nagano and NCTC 7096. This work highlighted the basis of differential biological control abilities between strains belonging to the same species and demonstrates techniques useful to the screening of effective biocontrol strains for environmentally friendly secondary metabolites that can be used to manage plant pathogens in the field.

Enhanced separation and analysis procedure reveals production of tri-acylated mannosylerythritol lipids by Pseudozyma aphidis

Mannosylerythritol lipids (MELs) are one of the most promising biosurfactants because of their high fermentation yields (>100 g l−1) and during the last two decades they have gained a lot of attention due to their interesting self-assembling properties and biological activities. In this study, MELs were produced by fed-batch bioreactor fermentation of rapeseed oil with Pseudozyma aphidis MUCL 27852. This high-level MEL-producing yeast secretes four conventional MEL structures, -A, -B, -C and -D, which differ in their degree of acetylation. During our research, unknown compounds synthesized by P. aphidis were detected by thin-layer chromatography. The unknown compounds were separated by flash chromatography and identified as tri-acylated MELs by high-performance liquid chromatography tandem mass spectrometry (HPLC–MS/MS). The third fatty acid chain on the tri-acylated MELs was positioned on the primary alcohol of the erythritol moiety and comprised long-chain acids, mainly oleic and linoleic acid, which are not found in conventional di-acylated MELs. Furthermore, the LC–MS analysis time of conventional MELs was reduced to almost one-third by switching from HPLC–MS/MS to ultraperformance liquid chromatography tandem mass spectrometry (UPLC–MS/MS). Provided optimization of the fermentation yield, P. aphidis could be an interesting novel producer of tri-acylated MELs and, thereby expand the supply and applicability of biosurfactants.

Biosurfactants: Promising Molecules for Petroleum Biotechnology Advances

The growing global demand for sustainable technologies that improves the efficiency of petrochemical processes in the oil industry has driven advances in petroleum biotechnology in recent years. Petroleum industry uses substantial amounts of petrochemical-based synthetic surfactants in its activities as mobilizing agents to increase the availability or recovery of hydrocarbons as well as many other applications related to extraction, treatment, cleaning, and transportation. However, biosurfactants have several potential applications for use across the oil processing chain and in the formulations of petrochemical products such as emulsifying/demulsifying agents, anticorrosive, biocides for sulfate-reducing bacteria, fuel formulation, extraction of bitumen from tar sands, and many other innovative applications. Due to their versatility and proven efficiency, biosurfactants are often presented as valuable versatile tools that can transform and modernize petroleum biotechnology in an attempt to provide a true picture of state of the art and directions or use in the oil industry. We believe that biosurfactants are going to have a significant role in many future applications in the oil industries and in this review therefore, we highlight recent important relevant applications, patents disclosures and potential future applications for biosurfactants in petroleum and related industries.

Production of lipopeptide biosurfactants by Bacillus atrophaeus 5-2a and their potential use in microbial enhanced oil recovery

Background

Lipopeptides are known as promising microbial surfactants and have been successfully used in enhancing oil recovery in extreme environmental conditions. A biosurfactant-producing strain, Bacillus atrophaeus 5-2a, was recently isolated from an oil-contaminated soil in the Ansai oilfield, Northwest China. In this study, we evaluated the crude oil removal efficiency of lipopeptide biosurfactants produced by B. atrophaeus 5-2a and their feasibility for use in microbial enhanced oil recovery.

Results

The production of biosurfactants by B. atrophaeus 5-2a was tested in culture media containing eight carbon sources and nitrogen sources. The production of a crude biosurfactant was 0.77 g L⁻¹ and its surface tension was 26.52 ± 0.057 mN m⁻¹ in a basal medium containing brown sugar (carbon source) and urea (nitrogen source). The biosurfactants produced by the strain 5-2a demonstrated excellent oil spreading activity and created a stable emulsion with paraffin oil. The stability of the biosurfactants was assessed under a wide range of environmental conditions, including temperature (up to 120 °C), pH (2–13), and salinity (0–50 %, w/v). The biosurfactants were found to retain surface-active properties under the extreme conditions. Additionally, the biosurfactants were successful in a test to simulate microbial enhanced oil recovery, removing 90.0 and 93.9 % of crude oil adsorbed on sand and filter paper, respectively. Fourier transform infrared spectroscopy showed that the biosurfactants were a mixture of lipopeptides, which are powerful biosurfactants commonly produced by Bacillus species.

Conclusions

The study highlights the usefulness of optimization of carbon and nitrogen sources and their effects on the biosurfactants production and further emphasizes on the potential of lipopeptide biosurfactants produced by B. atrophaeus 5-2a for crude oil removal. The favorable properties of the lipopeptide biosurfactants make them good candidates for application in the bioremediation of oil-contaminated sites and microbial enhanced oil recovery process.

Utilization of Paneer Whey Waste for Cost-Effective Production of Rhamnolipid Biosurfactant

The present study aimed at isolating rhamnolipid biosurfactant-producing bacteria that could utilize paneer whey, an abundant waste source as sole medium for the production purpose. Pseudomonas aeruginosa strain, SR17, was isolated from hydrocarbon-contaminated soil that could efficiently utilize paneer whey for rhamnolipid production and reduce surface tension of the medium from 52 to 26.5 mN/m. The yield of biosurfactant obtained was 2.7 g/l, upgraded to 4.8 g/l when supplemented with 2 % glucose and mineral salts. Biochemical, FTIR, and LC-MS analysis revealed that extracted biosurfactant is a combination of both mono and di-rhamnolipid congeners. The critical micelle concentration (CMC) was measured to be 110 mg/l. Emulsification activity of the biosurfactant against n-hexadecane, olive oil, kerosene, diesel oil, engine oil, and crude oil were found to be 83, 88, 81, 92, 86, and 100 %, respectively. The rhamnolipid was detected to be non-toxic against mouse fibroblastic cell line L292.

Biosurfactant as a Promoter of Methane Hydrate Formation: Thermodynamic and Kinetic Studies

Natural gas hydrates (NGHs) are solid non-stoichiometric compounds often regarded as a next generation energy source. Successful commercialization of NGH is curtailed by lack of efficient and safe technology for generation, dissociation, storage and transportation. The present work studied the influence of environment compatible biosurfactant on gas hydrate formation. Biosurfactant was produced by Pseudomonas aeruginosa strain A11 and was characterized as rhamnolipids. Purified rhamnolipids reduced the surface tension of water from 72 mN/m to 36 mN/m with Critical Micelle Concentration (CMC) of 70 mg/l. Use of 1000 ppm rhamnolipids solution in C type silica gel bed system increased methane hydrate formation rate by 42.97% and reduced the induction time of hydrate formation by 22.63% as compared to water saturated C type silica gel. Presence of rhamnolipids also shifted methane hydrate formation temperature to higher values relative to the system without biosurfactant. Results from thermodynamic and kinetic studies suggest that rhamnolipids can be applied as environment friendly methane hydrate promoter.

Bacterial degradation of crude oil using solid formulations of bacillus strains isolated from oil-contaminated soil towards microbial enhanced oil recovery application

Microbial enhanced oil recovery has played a major role in enhancing crude oil recovery from depleted oil reservoirs to solve stagnant petroleum production.