Surfactin from Bacillus velezensis H2O-1: Production and Physicochemical Characterization for Postsalt Applications

The use of surfactin, a powerful biosurfactant, is generally hampered by poor production yield. Consequently, identification of new producers and the study of operational parameters are essential. We identify Bacillus sp. H2O-1 as Bacillus velezensis, a species previously not investigated for its biosurfactant production. Among the nitrogen sources we tested, (NH₄)₂SO₄ and NH₄NO₃ were the most appropriate for surfactin production, reaching 608.5 and 659.5 mg L⁻¹, respectively. Only temperature affected the production, whereas rotation and the C/N ratio did not. Biosurfactants can be used in enhanced oil recovery (EOR) in reservoirs located in the presalt and postsalt layers, where conditions of temperature, pressure, and salinity are quite varied, requiring a study of the stability of these molecules under these conditions. We found the surfactin produced by B. velezensis to be stable at different temperatures, pH, and ionic strengths. We evaluated the concurrent effects of different salinity, temperature, and pressure conditions on surface and interfacial activities of this surfactin. Overall, we found the surfactin produced by B. velezensis H2O-1 to have considerable potential for industrial applications, mainly due to the stability of its physical and chemical characteristics when subjected to different temperatures, pressures, and salinities, in addition to its low toxicity.     

Studies on Biosurfactants Produced using Bacillus cereus Isolated from Seawater with Biotechnological Potential for Marine Oil-Spill Bioremediation

With the aim of producing a biotensioactive material for use in the remediation of marine environments, screening for biosurfactant-producing bacteria was conducted with strains isolated from seawater contaminated with petroleum derivatives. Gene sequencing revealed that all four promising biosurfactant-producing isolates belonged to the same genus and species, namely Bacillus cereus. The biosurfactant-producing bacteria were cultivated with different carbon (glucose, soybean oil, and waste frying soybean oil) and nitrogen (ammonium chloride, sodium nitrate, urea, and peptone) sources. B. cereus strain BCS0 was chosen as the best biosurfactant producer in a mineral medium with 2% frying oil and 0.12% peptone. Following the optimization of agitation and cultivation time, an agitation rate of 250 rpm and 48 h of cultivation were selected. Under these conditions, the surface tension was reduced to 27 mN m⁻¹ and the biosurfactant concentration was 3.5 g L⁻¹. The critical micelle concentration (CMC) of the biosurfactant was defined as 500 mg L⁻¹. The biosurfactant remained stable within large ranges of pH (2–10), salinity (2–10%), and temperature (5–120 °C). Under these conditions, motor oil emulsification rates were greater than 90%. Moreover, the biosurfactant properties remained unaltered after heating at 90 °C for 120 min. The biosurfactant enhanced the degradation of motor oil up to 96% in 27 days and exhibited considerable motor oil displacement capacity. Thus, the biosurfactant has potential in the application of remediation processes in marine environments.     

Structural characterization of a biosurfactant produced by Bacillus subtilis at 45°C

Structural and biochemical characterization of a biosurfactant produced by Bacillus subtilis under thermophilic conditions was performed. Preliminary structural determination of CHCl₃/CH₃OH (65∶15) extracts by thin-layer chromatographic reagents showed it to be identical to surfactin. Also, the infrared, ¹H nuclear magnetic resonance, and mass spectroscopy analysis confirmed it to be identical to surfactin. Biochemically, the surfactant was a lipopeptide-containing lipid (17.05%) and protein (13.2%). The surfactant yielded a minimal aqueous surface-tension value of 28 dyne/cm and an interfacial tension value at 0.1% concentration of 0.2 dyne/cm against diesel oil. The critical micelle concentration of the surfactant was 35 mg/L. The biosurfactant exhibited an emulsification value (E ₂₄) of 90 against diesel oil and a sand-pack oil recovery of 62%. It has potential application in microbial-enhanced oil recovery in thermophilic, alkaline, acidic, and halophilic environments.     

Production and stability studies of the biosurfactant isolated from marine Nocardiopsis sp. B4

A potential biosurfactant producing strain, marine Nocardiopsis B4 was isolated from the West coast of India. Culture conditions involving variations in carbon and nitrogen sources were examined at constant pH, temperature and revolutions per min (rpm), with the aim of increasing productivity in the process. The biosurfactant production was followed by measuring the surface tension, emulsification assay and emulsifying index E24. Enhanced biosurfactant production was carried out using olive oil as the carbon source and phenyl alanine as the nitrogen source. The maximum production of the biosurfactant by Nocardiopsis occurred at a C/N ratio of 2:1 and the optimized bioprocess condition was pH 7.0, temperature 30° C and salt concentration 3%. The production of the biosurfactant was growth dependent. The surface tension was reduced up to 29 mN/m as well as the emulsification index E24 was 80% in 6 to 9 days. Properties of the biosurfactant that was separated by acid precipitation were investigated. The biosurfactant activity was stable at high temperature, a wide range of pH and salt concentrations thus, indicating its application in bioremediation, food, pharmaceutical and cosmetics industries.     

Biosurfactant-and-Bioemulsifier Produced by a Promising Cunninghamella echinulata Isolated from Caatinga Soil in the Northeast of Brazil

A Mucoralean fungus was isolated from Caatinga soil of Pernambuco, Northeast of Brazil, and was identified as Cunninghamella echinulata by morphological, physiological, and biochemical tests. This strain was evaluated for biosurfactant/bioemulsifier production using soybean oil waste (SOW) and corn steep liquor (CSL) as substrates, added to basic saline solution, by measuring surface tension and emulsifier index and activity. The best results showed the surface water tension was reduced from 72 to 36 mN/m, and an emulsification index (E₂₄) of 80% was obtained using engine oil and burnt engine oil, respectively. A new molecule of biosurfactant showed an anionic charge and a polymeric chemical composition consisting of lipids (40.0% w/w), carbohydrates (35.2% w/w) and protein (20.3% w/w). In addition, the biosurfactant solution (1%) demonstrated its ability for an oil displacement area (ODA) of 37.36 cm², which is quite similar to that for Triton X-100 (38.46 cm²). The stability of the reduction in the surface water tension as well as of the emulsifier index proved to be stable over a wide range of temperatures, in pH, and in salt concentration (4%–6% w/v). The biosurfactant showed an ability to reduce and increase the viscosity of hydrophobic substrates and their molecules, suggesting that it is a suitable candidate for mediated enhanced oil recovery. At the same time, these studies indicate that renewable, relatively inexpensive and easily available resources can be used for important biotechnological processes.     

Formulation of ultralow interfacial tension systems using extended surfactants

Inspired by the concept of lipophilic and hydrophilic linkers, extended surfactants have been proposed as highly desirable candidates for the formulation of microemulsions with high solubilization capacity and ultralow interfacial tension (IFT), especially for triglyceride oils. The defining characteristic of an extended surfactant is the presence of one or more intermediate-polarity groups between the hydrophilic head and the hydrophobic tail. Currently only limited information exists on extended surfactants; such knowledge is especially relevant for cleaning and separation applications where the cost of the surfactant and environmental regulations prohibit the use of concentrated surfactant solutions. In this work, we examine surfactant formulations for a wide range of oils using dilute solutions of the extended surfactant classes sodium alkyl polypropyleneoxide sulfate (R-(PO) _x −SO₄Na), and sodium alkyl polypropyleneoxide-polyethyleneoxide sulfate (R-(PO) _y -(EO) _z −SO₄Na). The IFT of these systems was measured as a function of electrolyte and surfactant concentration for polar and nonpolar oils. The results show that these extended surfactant systems have low critical micelle concentrations (CMC) and critical microemulsion concentrations (CμC) compared with other surfactants. We also found that the unique structure of these extended surfactants allows them to achieve ultralow IFT with a wide range of oils, including highly hydrophobic oils (e.g., hexadecane), triolein, and vegetable oils, using only ppm levels of these extended surfactants. It was also found that the introduction of additional PO and EO groups in the extended surfactant yielded lower IFT and lower optimum salinity, both of which are desirable in most formulations. Based on the optimum formulation conditions, it was found that the triolein sample used in these experiments behaved as a very polar oil, and all other vegetable oils displayed very hydrophobic behavior. This unexpected triolein behavior is suspected to be due to uncharacterized impurities in the triolein sample, and will be further evaluated in future research.     

Synthesis of Didodecylmethylcarboxyl Betaine and Its Application in Surfactant–Polymer Flooding

Enhanced crude oil recovery by chemical flooding has been a main measure for postponing the overall decline of crude oil output in China, and surfactant-polymer (SP) flooding may replace alkali-surfactant-polymer flooding in the future for avoiding the undesired effects of using alkali. In this paper the synthesis of a surfactant with a large hydrophobe, didodecylmethylcarboxyl betaine (diC₁₂B), and its adaptability in SP flooding were investigated. The results show that diC₁₂B can be synthesized by reaction of didodecylmethyl amine, a product commercially available, with chloroacetic acid in the presence of NaOH, with a resulting yield as high as 80?wt% under appropriate conditions. With double dodecyl chain diC₁₂B is highly surface active as displayed by its low CMC, 3.7?×?10^?6?mol?L^?1, low ??_CMC, 27?mNm^?1, as well as high adsorption and small cross section area (??0.25?nm²) at both air/water and oil/water interfaces at 25?°C. By mixing with conventional hydrophilic surfactants diC₁₂B can be well dissolved in Daqing connate water and reduce the Daqing crude oil/connate water interfacial tension to about 10^?3?mN?m^?1 at 45?°C in a wide total surfactant concentration range, from 0.01 to 0.5 wt%. And a tertiary oil recovery, 18?±?1.5?% OOIP, can been achieved by SP flooding using natural cores without adding any alkaline agent or neutral electrolyte. DiC₁₂B seems thus to be a good surfactant for enhanced oil recovery by SP flooding.     

Synthesis of an Alkyl Polyoxyethylene Ether Sulfonate Surfactant and Its Application in Surfactant Flooding

Surfactant flooding as a potential enhanced oil‐recovery technology in a high‐temperature and high‐salinity oil reservoir after water flooding has attracted extensive attention. In this study, the synthesis of an alkyl alcohol polyoxyethylene ether sulfonate surfactant (C₁₂EO₇S) with dodecyl alcohol polyoxyethylene ether and sodium 2‐chloroethanesulfonate monohydrate, and its adaptability in surfactant flooding were investigated. The fundamental parameters of C₁₂EO₇S were obtained via surface tension measurement. And the ability to reduce oil–water interfacial tension (IFT), wettability alteration, emulsification, and adsorption was determined. The results illustrated that IFT could be reduced to 10^?3 mN m^?1 at high temperature and high salinity without additional additives, and C₁₂EO₇S exhibited benign wettability alternate ability, and emulsifying ability. Furthermore, the oil‐displacement experiments showed that C₁₂EO₇S solution could remarkably enhance oil recovery by 16.19% without adding any additives.     

Isolation,characterization, and antifungal application of a biosurfactant produced by Enterobacter sp. MS16

Isolate MS16 obtained from diesel contaminated soil, identified as Enterobacter sp. using 16S rRNA gene analysis produced biosurfactant when grown on unconventional substrates like groundnut oil cake, sunflower oil, and molasses. Of these carbon substrates used, sunflower oil cake showed highest biosurfactant production (1.5 g/L) and reduction in surface tension (68%). The biosurfactant produced by MS16 efficiently emulsified various hydrocarbons. The carbohydrates and fatty acids of the biosurfactants were studied using TLC, FTIR, NMR, and GC‐MS. The carbohydrate composition as determined by GC‐MS of their alditol acetate derivatives showed the predominance of glucose, galactose and arabinose, and hydroxyl fatty acids of chain length of C₁₆ and C₁₈ on the basis of FAMEs analysis. Biosurfactant showed antifungal activity and inhibited the fungal spore germination. Practical applications : Enterobacter sp., MS16 produces a biosurfactant composed of carbohydrates and fatty acids which exhibits excellent surface active properties. Use of industrial wastes for biosurfactant production is economical and facilitates the industrial production of this biosurfactant which has potential antifungal activity.     

Effects of various nutritional supplements on biosurfactant production by a strain of <Emphasis Type="Italic">Bacillus subtilis</Emphasis> at 45°C

Effects of various factors on growth and biosurfactant production by Bacillus subtilis MTCC 2423 were studied. Sucrose (2%) and potassium nitrate (0.3%) were the best carbon and nitrogen sources. The addition of various metal supplements (magnesium, calcium, iron, and trace elements) greatly affected growth and biosurfactant production. The effect of the metal cations, used together, is greater than when they are used individually. The biosurfactant production increased considerably (almost double) by addition of metal supplements. Very high concentrations of metal supplements, however, inhibited biosurfactant production. Amino acids such as aspartic acid, asparagine, glutamic acid, valine, and lysine increased the final yield of biosurfactant by about 60%. The organism could produce biosurfactant at 45°C and within the pH range of 4.5–10.5. The biosurfactant was thermostable and pH stable (from 4.0 to 12.0). The capability of the organism to produce biosurfactant under thermophilic, alkaliphilic, and halophilic conditions makes it a suitable candidate for field applications. Infrared, nuclear magnetic resonance, and mass spectroscopy studies showed the surfactant to be identical to surfactin.     

Biosurfactant Production by Bacillus tequilensis ZSB10: Structural Characterization,Physicochemical, and Antifungal Properties

A new biosurfactant was obtained from a moderately halophilic bacterium identified as Bacillus tequilensis ZSB10 that was isolated from a saline water pond located in Tehuacan-Cuicatlan valley, Mexico. A kinetic analysis of the bacterial growth of the ZSB10 strain showed a maximum growth at 24 h regardless of the initial pH (5, 7.4, and 9). The best results were found at pH = 7.4 in terms of bacterial growth, besides which the produced biosurfactant showed emulsifying and surfactant properties with an emulsification index (E₂₄) and surface tension change (ΔST) of 54 ± 0% and 26 mN m⁻¹, respectively. Extracted ZSB10 crude biosurfactant had a yield of 106 ± 6 mg L⁻¹, an E₂₄ = 58.4 ± 0.2%, and a ΔST = 26 mN m⁻¹ with a critical micelle concentration (CMC) of 44.82 mg L⁻¹. Also, its structure was characterized by MALDI-TOF mass spectrometry as a surfactin, iturin A, and fengycin mixture whose main isoform was leu/ile-7 C₁₅ surfactin [M + Na]⁺. Finally, the ZSB10 crude biosurfactant showed antifungal activity against Helminthosporium sp., with a 79.3% growth inhibition and an IC₅₀ of 1.37 mg per disc. Therefore, this biosurfactant could be used as biopesticide.     

一株耐温耐盐烃降解菌Geobacillus sp. XDF-4性能

从大庆油田龙虎泡区块采油地层水中分离得到一株性能很好的耐盐耐温的兼性烃降解菌XDF-4,经形态观察、生理生化实验和16SrDNA基因序列分析,初步鉴定为地芽孢杆菌Geobacillus sp.。该菌在45～75℃、pH 6.5～9.0、盐的质量分数0～10%下生长良好,其最适生长温度为65℃,最适盐的质量分数为 3.0%。研究发现,该菌株能以原油为唯一碳源生长并合成生物表面活性剂, 发酵相似文献   

Interfacial Rheology Measured with a Spinning Drop Interfacial Rheometer: Particularities in More Realistic Surfactant–Oil–Water Systems Close to Optimum Formulation at HLDN = 0

Three different cases were selected to study the effect of physicochemical formulation on interfacial rheology properties of surfactant–oil–water (SOW) systems by increasing the complexity of the system from a basic case. This was performed by changing the normalized hydrophilic–lipophilic deviation (HLD_N) to attain the optimum formulation at HLD_N = 0. Two types of SOW systems were studied: the first one used an ionic surfactant with a salinity scan, and the second one a mixture of two nonionic surfactants in a formulation scan produced by changing their proportion. Both of them contained cyclohexane as a pure oil phase, without alcohol. Sec-butanol was then added as a co-surfactant with hardly any formulation influence on HLD_N. The complexity in interfacial rheology was then increased by changing the oil to a light crude with low asphaltene content. The interfacial rheology is also reported for a realistic system with a high asphaltene content comprised of crude oil diluted in cyclohexane with a conventional surfactant and a commercial demulsifier. The findings confirm that at optimum formulation and whatever the scanning variable (salinity, average ethylene oxide number in the nonionic surfactant mixture, or surfactant/demulsifier concentration), the interfacial tension, and interfacial elastic moduli E, E′, and E″ exhibit a deep minimum. These observations are related to the acceleration of the surfactant exchanges between the interface, oil, and water, near the optimum formulation. Several arguments are put forward to explain how these findings could contribute to the decrease in emulsion stability at HLD_N = 0.     

Biodegradability Study of the Biosurfactant Contained in a Crude Extract from Corn Steep Water

Over the last few years, the global biosurfactant market has raised due to the increasing awareness among consumers, for the use of biological or bio-based products. Because of their composition, it can be speculated that these are more biocompatible and more biodegradable than their chemical homologous. However, at the moment, no studies exist in the literature about the biodegradability of biosurfactants. In this work, a biosurfactant contained in a crude extract, obtained from a corn wet-milling industry stream that ferments spontaneously in the presence of lactic acid bacteria, was subjected to a biodegradation study, without addition of external microbial biomass, under different conditions of temperature (5–45 °C), biodegradation time (15–55 days), and pH (5–7). For that, a Box–Behnken factorial design was applied, which allowed to predict the percentage of biodegradation for the biosurfactant contained in the crude extract, between the range of the independent variables selected in the study, obtaining biodegradation values between 3 and 80%. The percentage of biodegradation for the biosurfactant was calculated based on the increase in the surface tension of samples of the crude extract. Furthermore, it was also possible to predict the variation in t_1/2 for the biosurfactant (time to achieve the 50% of biodegradation) under different conditions.     

Lauryl alcohol and amine oxide as foam stabilizers in the presence of hardness and oily soil

The effects of two potential foam boosters, n-dodecanol (or lauryl alcohol: LA) and tetradecyldimethylamine oxide (C₁₄DMAO), were investigated for two situations in which foam made from a 0.01 wt% solution of a common alkylethoxy sulfate surfactant was highly unstable in the presence of oil drops consisting of an n-hexadecane/oleic acid mixture. In one case in which dissolved CaCl₂ was present at alkaline pH, insoluble calcium oleate particles formed in situ and facilitated foam breakage. In the other, a much higher concentration of calcium was present at neutral pH, and drops of a microemulsion phase formed but no calcium oleate. In both cases, 0.005 wt% LA reduced the entry coefficient, E, of the oil to the air-water surface sufficiently to prevent drop entry and stabilized the foam. In contrast, 0.005 wt% C₁₄DMAO caused smaller reductions in E and was ineffective as a foam booster. LA was more effective because it was able to form a more compact monolayer with the surfactant than C₁₄DMAO at the air-water surface, which led to lower surface tensions and hence lower values of E.     

Utilization of molasses for biosurfactant production by two Bacillus strains at thermophilic conditions

Traditionally, biosurfactants have been produced from hydrocarbons. Some possible substitutes for microbial growth and biosurfactant production include urban wastes, peat hydrolysate, and agro-industrial by-products. Molasses, a nonconventional substrate (agro-industrial by-product) can also be used for biosurfactant production. It has been utilized by two strains of Bacillus subtilis (MTCC 2423 and MTCC1427) for biosurfactant production and growth at 45°C. As a result of biosurfactant accumulation, the surface tension of the medium was lowered to 29 and 31 dynes/cm by the two strains, respectively. This is the first report of biosurfactant production by strains of B. subtilis at 45°C. Potential application of the biosurfactant in microbial enhanced oil recovery is also presented.     

The effect of divalent cations (Ca++ and Mg++) on the optimal salinity and salt tolerance of petroleum sulfonate and ethoxylated sulfonate mixtures in relation to improved oil recovery

It was demonstrated that a surfactant formulation consisting of a petroleum sulfonate and an ethoxylate sulfonate can tolerate a large amount of CaCl₂ and MgCl₂ in solution without any precipitation or phase-separation. The stability of this surfactant formulation was not influenced significantly by the presence of divalent cations. The maximum salt concentration permissible for a stable formulation depended primarily on the ionic strength of the salt solution and not on the relative proportions of the divalent and monovalent cations. It was also observed that though the optimal salinity (Sγ) decreased upon increasing the amount of divalent cations, the interfacial tension at optimal salinity was always in the millidyne (≃10⁻³ dynes/cm) range. This study has a practical application in designing the surfactant formulations for tertiary oil recovery process for reservoirs consisting of high concentrations of mono- and divalent cataions.     

Economic production of Bacillus subtilis SPB1 biosurfactant using local agro‐industrial wastes and its application in enhancing solubility of diesel

BACKGROUND: The present work aimed to optimize a new economic medium for lipopeptide biosurfactant production by Bacillus subtilis SPB1 for application in the environmental field as an enhancer of diesel solubility. Statistical experimental designs and response surface methodology were employed to optimize the medium components. RESULTS: A central composite design was applied to increase the production yield and predict the optimal values of the selected factors. An optimal medium, for biosurfactant production of about 4.5 g L^?1, was found to be composed of sesame peel flour (33 g L^?1) and diluted tuna fish cooking residue (40%) with an inoculum size of 0.22. Increased inoculum size (final OD₆₀₀) significantly improved the production yield. The emulsifier produced was demonstrated to be an alternative to chemically synthesized surfactants since it shows high solubilization efficiency towards diesel oil in comparison with SDS and Tween 80. CONCLUSION: Optimization studies led to a strong improvement in production yield. The emulsifier produced, owing its high solubilization capacity and its large tolerance to acidic and alkaline pH values and salinity, shows great potential for use in bioremediation processes to enhance the solubility of hydrophobic compounds. © 2012 Society of Chemical Industry     

Dialkyl Sulfobetaine Surfactants Derived from Guerbet Alcohol Polyoxypropylene–Polyoxyethylene Ethers for SP Flooding of High Temperature and High Salinity Reservoirs

Dialkyl hydroxypropyl sulfobetaine (HSB) surfactants, C₁₆GA-(PO)₅-(EO)₃-HSB and C₂₄GA-(PO)₁₀-(EO)₁₀-HSB, were synthesized from Guerbet alcohols (GA) polyoxypropylene–polyoxyethylene (PO-EO) ethers and their behaviors in surfactant-polymer (SP) flooding of high temperature and high salinity reservoirs were examined and compared with their anionic hydroxypropyl sulfonate (HS) counterparts, C₁₆GA-(PO)₅-(EO)₃-HS and C₂₄GA-(PO)₁₀-(EO)₁₀-HS. The PO-EO chain embedded improves their aqueous solubility, and the sulfobetaines show better salt resistance than sulfonates. For a reservoir condition of total salinity 19,640 mg L⁻¹ and 60–80°C, C₁₆GA-(PO)₅-(EO)₃-HSB alone can reduce crude oil/connate water interfacial tension (IFT) to ultralow at 0.25–5 mM, which can be further widened to 0.1–5 mM by mixing with dodecylhexyl (C₁₂₊₆) glyceryl ether hydroxypropyl sulfobetaine (C₁₂₊₆GE-HSB), a slightly hydrophobic surfactant. C₂₄GA-(PO)₁₀-(EO)₁₀-HSB is more hydrophobic for the specified reservoir condition, however, by mixing with hexadecyl dimethyl hydroxypropyl sulfobetaine (C₁₆HSB), a hydrophilic surfactant, ultralow IFT can also be achieved at a total concentration of 0.25–5 mM. The anionic counterparts can also reduce IFT to ultralow by mixing with C₁₂₊₆GE-HSB and C₁₆HSB, respectively. Moreover, the optimum binary mixture, C₁₆GA-(PO)₅-(EO)₃-HSB/C₁₂₊₆GE-HSB at a molar fraction ratio of 0.6/0.4, can keep the negatively charged solid surface water-wet (θ_w = 12–23°) in a wide concentration range, and can still achieve ultralow IFT after stored at 90°C for 90 days (initially 5 mM), which overall are favor of improving oil displacement efficiency at high temperature and high salinity reservoir conditions.     

Optimization and Characterization of Biosurfactant Rhamnolipid Production by Pseudomonas aeruginosa Isolated from an Artificially Contaminated Soil

Biosurfactants are surfactants biologically produced by microorganisms, presenting several advantages when compared to synthetic surfactants. Pseudomonas aeruginosa is known for producing rhamnolipids, considered one of the most interesting types of biosurfactants due to their high yields, when compared to other types. In this work, the production of rhamnolipid from P. aeruginosa was optimized. At first, the Plackett–Burman design was used to select most significant variables affecting the biosurfactant production yield among nine variables—carbon–nitrogen ratio, carbon concentration, nitrogen source, pH, cultivation time, potassium and magnesium concentrations, agitation, and temperature. Then, using main variables, a central point experimental design aiming to optimize rhamnolipid production was performed. The maximum biosurfactant concentration obtained was 0.877 mg L⁻¹. The rhamnolipid also displayed a great emulsification rate, reaching approximately 67%, and the ability to reduce water surface tension from 72.02 to 35.26 mN m⁻¹ at a critical micelle concentration (CMC) of 127 mg L⁻¹, in addition to presenting a good stability when exposed to wide pH and salinity ranges. The results suggest that rhamnolipids are promising substitutes for synthetic surfactants, especially due to lower impacts on the environment.