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.     

Sunflower Acid Oil-Based Production of Rhamnolipid Using Pseudomonas aeruginosa and Its Application in Liquid Detergents

Utilization of industrial waste as substrates for the rhamnolipid synthesis by Pseudomonas aeruginosa is a worthy alternative for conventionally used vegetable oils and fatty acids to reduce the production cost of rhamnolipid. Sunflower acid oil (SAO), a by-product of the oil industry, contains 70% 18:0 fatty acid, with oleic acid as a major component. In this scope, production and analysis of rhamnolipid was successfully demonstrated using SAO as a new substrate. Pseudomonas aeruginosa produced rhamnolipid (a glycolipid biosurfactant) at a maximum concentration of 4.9 g L⁻¹ with 60 g L⁻¹ of SAO in the medium. Structural properties of rhamnolipid biosurfactant are confirmed using thin layer chromatography (TLC), high performance liquid chromatography (HPLC), and fourier transformed infrared spectroscopy (FTIR) analysis. Further surface-active properties of the crude rhamnolipid were evaluated by measuring surface tension and emulsification properties. The synthesized rhamnolipid reduced the surface tension of water to 30.12 mN m⁻¹ and interfacial tension (against heptane) to 0.52 mN m⁻¹. Moreover, rhamnolipid shows the highest emulsification index (above 80%) for vegetable oils. This study confirms the use of SAO as a potential substrate for rhamnolipid production. The synthesized rhamnolipid was incorporated in liquid detergent formulation along with alpha olefin sulfonate (AOS) and sodium lauryl ether sulfate (SLES). The performance properties including foaming and cleaning efficiency of liquid detergent were compared.     

Synthesis,Physico-Chemical Properties and Enhanced Oil Recovery Flooding Evaluation of Novel Zwitterionic Gemini Surfactants

In this work, a novel series of zwitterionic gemini surfactants with different hydrophobic tails were synthesized and characterized. The physico‐chemical properties of these products (such as surface tension, oil/water interfacial tension, foaming ability, and the wetting ability of paraffin‐coated sandstone) were fully studied. The CMC of the synthesized surfactants ranged from 2.17 × 10^?4 mol L^?1 to 5.36 × 10^?4 mol L^?1 and corresponding surface tension (γ_CMC) ranged from 26.49 mN m^?1 to 29.06 mN m^?1, which showed excellent efficiency among the comparison surfactants. All the products can reduce the interfacial tension to a relatively low level of about 0.1–1.0 mN m^?1. Additionally, results from applying different hydrocarbons suggested that the synergy will be clearer and oil/water interfacial tension will be lower if the oil components are similar to the surfactants. Contact angle and foaming measurements indicated that the surfactants exhibited good wetting and foaming abilities. The results of oil flooding experiments using an authentic sandstone microscopic model showed that C‐12 and CA‐12 could effectively improve the displacement efficiency by 21–29 %.     

Characterization of Biosurfactant Produced by a Novel Strain of Pseudomonas aeruginosa,Isolate ADMT1

Several biosurfactant‐producing bacterial strains were isolated from petroleum‐contaminated soil. The isolate ADMT1, identified as a new strain of Pseudomonas aeruginosa, was selected for further studies on the basis of oil displacement test and emulsification index (E24). The optimal parameters for production, determined by employing Box–Behnken design, were temperature 36.5 °C and pH 7. The environmental isolate ADMT1 produced significant amount of biosurfactant (1.7 g L^?1 in 72 h) in minimal salt medium (MSM) using dextrose as the sole carbon source. The E24 value and critical micelle concentration (CMC) of the biosurfactant was 100% and 150 mg L^?1, respectively. At CMC, the surface tension of water was reduced to 28.4 mN m^?1. The biosurfactant exhibited hemolytic activity and antibacterial activity against 8 reference strains of pathogenic bacteria, including 2 methicillin‐resistant Staphylococcus aureus strains (MRSA ATCC 562 and MRSA ATCC 43300), with minimum inhibitory concentration (MIC) of 0.4 and 0.2 mg mL^?1, respectively. The structure of biosurfactant was characterized by FTIR, ¹H, and ¹³C NMR spectroscopy. 7 di‐rhamnolipid (RL) congeners were identified in the biosurfactant by ultraperformance liquid chromatography–mass spectrometry analysis. The major congeners, which constituted 67% of the RL mixture, included Rha‐Rha‐C₁₀‐C₁₀, Rha‐Rha‐C₁₂‐C₁₀, and Rha‐Rha‐C_12:1‐C₁₀. The minor congeners were Rha‐Rha‐C₁₀‐C₈, Rha‐Rha‐C_10:1‐C₁₀, Rha‐Rha‐C₁₀‐C_14:1, and Rha‐Rha‐C₁₀‐C₁₄. The congener Rha‐Rha‐C₁₀‐C₁₄ is being reported for the first time from any species of Pseudomonas. The high surface activity and E24 value make the ADMT1‐RL a potential candidate for its use in detergents, environmental bioremediation, and as an emulsifier in the food industry.     

Culture Medium Evaluation Using Low-Cost Substrate for Biosurfactants Lipopeptides Production by Bacillus amyloliquefaciens in Pilot Bioreactor

Total biosurfactant production by Bacillus amyloliquefaciens IT45 was evaluated with different substrates concentrations in a culture medium. A central composite design (CCD) was developed to evaluate the influence of variables, including glucose syrup, yeast extract, and calcium chloride, on surface tension (ST), total biosurfactant production, and residual sugar (RS). As a result, the best observed results for ST, RS, and total biosurfactant production were 30 mN m⁻¹, 31%, and 5.5 g L⁻¹, respectively, after 48 h of fermentations carried out in batch operation process. Characterization of the biosurfactant identified the presence of surfactin. To validate the CCD experiments, fermentations were conducted in a 40 L pilot bioreactor. For this fermentation, the cellular growth was 3.0 × 10⁹ CFU mL⁻¹, surfactin production was 0.55 g L⁻¹, and RS was 28%. The results demonstrate that B. amyloliquefaciens IT45 has the potential to produce biosurfactants and does not require high concentrations of carbon and nitrogen sources for its development.     

Using Corn Husk Powder as a Novel Substrate to Produce a Surface Active Compound from Labrenzia aggregate KP‐5

In this study, surface active compound (SAC)‐producing bacterial isolates were evaluated for SAC production using corn husk powder (CHP) as a sole carbon source. From the 51 isolates screened, Labrenzia aggregate KP‐5 produced the highest SAC activity. The highest SAC production (3.51 g L^?1) was obtained when the strain was cultivated in a minimal salt medium containing 40 g L^?1 CHP and 1 g L^?1 commercial monosodium glutamate at 30 °C and 150 rpm after 51 h of cultivation. The produced SAC had the ability to decrease the surface tension of water from 72.0 to 25.5 mN m^?1, with the critical micelle concentration of 9 mg L^?1 (11.07 mM) and exhibited the highest emulsification activity (EA) of 81% against motor oil. The SAC showed stability at 4–121 °C and pH 4–10 against the surface and EA of vegetable oils and hydrocarbons, and showed tolerance at high salt concentrations (1–10% NaCl). The chemical structure of the SAC was confirmed as a rhamnolipid using Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and mass spectrometric analysis. The SAC did not exhibit inhibitory effects on various vegetables tested; however, strong inhibitory activity against Gram‐positive and Gram‐negative bacteria was observed. The application of SAC for microbial enhanced oil recovery by sand saturated with used lubricating oil resulted in above 89% of oil removal. The properties of the SAC we obtained from CHP have potential applications especially for microbial enhanced oil recovery and/or reducing the intensity of environmental contamination. In addition, the obtained SAC is a suitable alternative to antimicrobial agents.     

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.     

Production of surface-active sophorolipid biosurfactant and crude oil degradability by novel Rhodotorula mucilaginosa strain SKF2

Biosurfactants are produced by important types of microorganisms such as bacteria, yeast, and filamentous fungi and have been used in a variety of industries. Among the 15 crude oil-degrading fungi, the two molds and one yeast were identified by 18S rDNA sequences as Mucor circinelloides strain SKMC, Fusarium fujikuroi strain DB2, and Rhodotorula mucilaginosa strain SKF2. These strains were isolated from crude oil–contaminated soil, diesel oil–contaminated soil, and activated sludge in the Oil Refinery Plant in Isfahan, Iran, respectively. The yeast strain was identified as a novel crude oil–degrading and biosurfactant-producing fungi in the presence of (1% v/v) Iranian light crude oil in the minimal salt medium (MSM). The highest amount of the dry weight of produced biosurfactant was measured at 6.2 g L⁻¹. Chemical nature of produced biosurfactant was determined as a surface-active sophorolipid biosurfactant compound by thin-layer chromatography, Fourier transform infra-red spectroscopy, and gas chromatography–mass spectrometry (GC–MS) analysis. The residual hydrocarbons in the MSM were analyzed by GC–MS, and it was shown that octadecane and docosane were eliminated by this novel strain completely.     

Synthesis,Characterization and Properties of <Emphasis Type="Italic">N</Emphasis>-Alkyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-di(2-hydroxyethyl) Amine Oxides

N‐Dodecyl‐N,N‐di(2‐hydroxyethyl) amine oxide (C₁₂DHEAO) and N‐stearyl‐N,N‐di(2‐hydroxyethyl) amine oxide (C₁₈DHEAO) were synthesized with N‐alkyl‐diethanolamine and hydrogen peroxide. Their chemical structures were confirmed using ¹H‐NMR spectra, mass spectral fragmentation and FTIR spectroscopic analysis. It was found that C₁₂DHEAO and C₁₈DHEAO reduced the surface tension of water to a minimum value of approximately 28.75 mN m^?1 at concentration of 2.48 × 10^?3 mol L^?1 and 32.45 mN m^?1 at concentration of 5.21 × 10^?5 mol L^?1, respectively. The minimum interfacial tension (IFT_min) and the dynamic interfacial tension (DIT) of oil–water system were measured. When C₁₈DHEAO concentration was in the range of 0.1–0.5%, the IFT_min between liquid paraffin and C₁₈DHEAO solutions all reached the ultra‐low interfacial tension. Furthermore, their foam properties were investigated by Ross‐Miles method, and the height of foam of C₁₂DHEAO was 183 mm. It was also found that they showed strong emulsifying power.     

Chicken Tallow,a Renewable Source for the Production of Biosurfactant by Yarrowia lipolytica MTCC9520, and its Application in Silver Nanoparticle Synthesis

The present study is focused on the production of a biosurfactant using Yarrowia lipolytica MTCC 9520 by employing inexpensive lipid waste, chicken tallow from slaughterhouses. Plackett–Burman and Box–Behnken Design analyses were adopted for preliminary screening of medium variables and further optimization. The maximal yield of 4.4 g L⁻¹ of the biosurfactant was obtained from the optimized medium. The highest emulsification activity was found to be 55%, and the surface tension decreased to 37 mN m⁻¹ at the end of 96 h. The critical micelle concentration of the biosurfactant was calculated as 1.2%. The produced biosurfactant was characterized as cationic lipoprotein in type, and the proteins present in the biosurfactant were observed to have molecular weights between 75 and 100 kDa. The fatty acids composition of the biosurfactant was detected by gas chromatography–mass spectrometry (GC–MS) analysis. Fourier transform infra red (FTIR) and nuclear magnetic resonance (NMR) analysis confirmed the lipoprotein nature of the extracted biosurfactant. Thermogravimetric (TG) and differential scanning calorimetry (DSC) analysis revealed the thermostable nature of the extracted biosurfactant. Surface plasmon resonance vibration peak at 421 nm was observed for the surfactant-stabilized silver nanoparticles (AgNP) through UV–Vis spectrophotometry. The average particle size of the synthesized AgNP was calculated as 7.2 ± 0.4 nm from transmission electron microscopy (TEM) analysis. Energy dispersive x-ray (EDX) spectroscopy exhibited the presence of silver in the synthesized nanoparticles. The zeta potential value of the synthesized AgNP was measured as −22.2 mV, and the polydispersity index was found as 2.3 through dynamic light scattering (DLS) analysis.     

Isolation and Identification of Current Biosurfactant-Producing Microbacterium maritypicum ABR5 as a Candidate for Oily Sludge Recovery

Biosurfactants have a wide range of applications in different areas, including petroleum microbiology and environmental biotechnology. In this study, removing and recovering oil from oily sludge using microbactan-producing bacteria have been investigated. The best biosurfactant-producing isolate was obtained from a petroleum reservoir and was identified by 16S rDNA analysis as Microbacterium maritypicum ABR5. Its 16S rDNA sequence was deposited in GenBank, NCBI under the accession number MK100468. Chemical analysis using thin-layer chromatography and Fourier Transform Infrared confirmed that the produced biosurfactant was glycolipoprotein. The strain reduced surface tension from 72 to 34.6 mN m⁻¹. The addition of 5 mg L ZnO nanoparticles to the biosurfactant-producing medium showed no bacterial toxicity effect and raised the emulsification index to 25.7%. Higher concentrations of ZnO nanoparticles, such as 10 and 100 mg L, decreased the bacterial growth rate and biosurfactant production. The mixing of M. maritypicum ABR5 culture medium and oily sludge increased the oil recovery from oily sludge by up to 70% after 5 days of incubation. This is the first report of biosurfactant production by a newly identified strain, M. maritypicum ABR5, isolated from a petroleum reservoir. We proposed that the isolated biosurfactant-producing strain could be considered an economical asset for oil recovery from oily sludge in the petroleum industry and environmental biotechnology.     

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.     

Recycling of Bakery Waste as an Alternative Carbon Source for Rhamnolipid Biosurfactant Production

Production of a rhamnolipid biosurfactant (RBS) using discarded mixed bakery waste (BW) employing bacterial strain Pseudomonas aeruginosa strain PG1 (identified by 16 s rDNA sequencing) was investigated for bioconversion of the food waste. Dry and powder form BW was supplemented with mineral salt media (MSM) as a sole carbon source for production of RBS. RBS production was measured based on the drop collapse assay and surface tension (ST) reduction of the culture media. Production of RBS in the culture media was enhanced by optimizing the carbon source (BW) concentration and the proper nitrogen source along with the pH of the MSM. Under optimized culture conditions, 11.56 g L⁻¹ day⁻¹ crude biosurfactant (BS) was achieved. The RBS had the ability to reduce the ST of the optimized MSM from 72.0 to 25.8 mN m⁻¹ during culture, where the critical micelle concentration (CMC) of the biosurfactant was found to be 100 mg L⁻¹. Liquid Chromatography Mass Spectroscopy (LC-MS), Fourier Transform Infrared spectroscopy (FTIR), and scanning electron microscopy (SEM)–energy dispersive X-ray spectroscopy (EDS) analyses of the purified BS confirmed that it is of rhamnolipid in nature and it is made up of both monorhamnolipid and dirhamnolipid congeners. Furthermore, the RBS did not express any cytotoxic effect on the cell line of mouse L292 fibroblastic cell indicating the biosafety nature of the high-value biomolecule.     

A Comparative Study of O/W Nanoemulsions Using Extra Virgin Olive or Olive‐Pomace Oil: Impacts on Formation and Stability

Nanoemulsions are considered an innovative approach for industrial food applications. The present study explored the potential use of olive‐pomace oil (OPO) for oil‐in‐water (o/w) nanoemulsion preparations and compared the effectiveness of extra virgin olive oil (EVOO) and OPO at nanoemulsion formulations. The ternary‐phase diagrams were constructed and the o/w nanoemulsions properties were evaluated in relation to their composition. The results showed that it is possible to form OPO nanoemulsions using Polysorbate 20 or Polysorbate 40. Nanoemulsions with EVOO and OPO presented desirable properties, in terms of kinetic stability (emulsion stability index % [ESI%]), mean droplet diameter (MDD), polydispersity index (PDI), ζ‐potential, viscosity, and turbidity. EVOO exhibited lower surface and interfacial tension forming nanoemulsions with a high ESI% and a low MDD. However, OPO led to nanoemulsions with a high ESI% but with a higher MDD. It was observed that by increasing the emulsifier concentration the MDD decreased, while increasing the dispersed phase concentration led to a higher MDD and a lower ESI%. Finally, nanoemulsions with the smallest MDD (99.26 ± 4.20 nm) and PDI (0.236 ± 0.010) were formed using Polysorbate 40, which presented lower surface and interfacial tension. Specifically, the nanoemulsion with 6 wt% EVOO and 6 wt% Polysorbate 40 demonstrated an interfacial tension of 51.014 ± 0.919 mN m^?1 and an MDD of 99.26 ± 4.20 nm. However, the nanoemulsion with 6 wt% OPO and 8 wt% Polysorbate 20 presented an interfacial tension of 54.308 ± 0.089 mN m^?1 and an MDD of 340.5 ± 7.1 nm.     

Bioremediation of Polycyclic Aromatic Hydrocarbon Contaminated Soil by a Microbial Consortium through Supplementation of Biosurfactant Produced by Pseudomonas aeruginosa Strain

Lipopeptide biosurfactant produced by Pseudomonas aeruginosa Lbp 3 strain isolated from petroleum contaminated soil was investigated for its potential to enhance bioavailability, and hence, the biodegradation of polycyclic aromatic hydrocarbons (PAHs) in contaminated soil microcosms. Experiments were conducted on a soil spiked with equal parts of the PAHs Phenanthrene, Fluoranthene, and Pyrene to a final concentration of 1200 mg of total PAHs per kg of dry soil. To evaluate biodegradation enhancement efficiency, 50 g spiked soil samples were supplemented with 50 mgL^?1, 100 mgL^?1, 300 mgL^?1, and 1000 mgL^?1of lipopeptide dissolved in 30 mL of MSM, and incubated for 40 days at 30°C in darkness. Statistically significant (P < 0.05) biodegradation rates were observed in all the amended microcosms in comparison to the unamended controls. Maximal biodegradations (> 96% of Phenanthrene and Fluoranthene and > 93% of Pyrene) were observed in the soil microcosms supplemented with 1000 mgL^?1and 50 mgL^?1 lipopeptide. The effect of substrate interactivity of the PAHs on the biodegradation kinetics was also tested in comparison with sole substrate microcosms. Competitive inhibition of the biodegradation of low molecular weight PAHs was observed as a result of substrate interactivity in the multisubstrate system.     

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.     

A Zwitterionic Surfactant Bearing Unsaturated Tail for Enhanced Oil Recovery in High‐Temperature High‐Salinity Reservoirs

High‐temperature/high‐salinity (HTHS) reservoirs contain a significant fraction of the world's remaining oil in place and are potential candidates for enhanced oil recovery (EOR). Selection of suitable surfactants for such reservoirs is a challenging task. In this work, two synthesized zwitterionic surfactants bearing a saturated and an unsaturated tail, namely 3‐(N‐stearamidopropyl‐N,N‐dimethyl ammonium) propanesulfonate and 3‐(N‐oleamidopropyl‐N,N‐dimethyl ammonium) propanesulfonate, respectively, were evaluated. The surfactant with the unsaturated tail showed excellent solubility in synthetic seawater (57,643 ppm) and in formation brine (213,734 ppm). However, the unsaturated surfactant with a saturated tail showed poor solubility, and therefore it was not evaluated further. The thermal stability of the synthesized unsaturated surfactant solution in seawater was evaluated by heating the solution at 90 °C in a sealed aging tube for 2 weeks. The thermal stability of the unsaturated surfactant was confirmed by FTIR and NMR analysis of the aged samples at such harsh conditions. The critical micelle concentration (CMC) of the synthesized unsaturated surfactant in seawater was 1.02 × 10^?4 mol L^?1, while the surface tension at CMC was 30 mN m^?1. The synthesized unsaturated surfactant was able to reduce the oil–water interfacial tension to ~10^?1 mN m^?1 at different conditions. A commercial copolymer of acrylamide and 2‐acrylamido‐2‐methylpropane sulfonic acid (AM‐AMPS) was tested for EOR applications in HTHS conditions. The addition of the synthesized unsaturated surfactant to the AM‐AMPS copolymer increased the viscosity of the system. The increase in oil recovery by injecting the unsaturated surfactant solution and the surfactant–polymer mixture in solution was 8 and 21%, respectively. The excellent properties of the synthesized unsaturated surfactant show that surfactants with an unsaturated tail can be an excellent choice for HTHS reservoirs.     

Synthesis and Properties of Sodium Mono-Alkylamide Phthalate Surfactants

The synthesis of a series of sodium mono-alkylamide phthalate surfactants is described, and the surface activity properties of the surfactants are reported. The mono-alkylamide phthalic acids were synthesized by amidation using primary aliphatic amines (lauryl, myristyl, cetyl) and phthalic anhydride as starting material. They were structurally characterized by IR, ¹H NMR and MS. The sodium mono-alkylamide phthalate surfactants were prepared by neutralization of the precursor acids with sodium hydroxide. They reduced the surface tension of water to 30?C38 mN?m^?1 at concentration levels of 10^?4?mol?L^?1.     

Biosurfactant production by <Emphasis Type="Italic">Bacillus coagulans</Emphasis>

A new biosurfactant producer, Bacillus coagulans, was isolated from soil. Its 24-h-old culture broth had a low surface tension (27–29 mN/m). Optimization of cell growth of this bacterium led to maximal biosurfactant production with glucose or starch as the organic carbon source, a pH in the range 4.0–7.5, and incubation temperatures from 20 to 45°C. The crude biosurfactants obtained after neutralization and lyophilization of the acid precipitate yielded a minimal aqueous solution surface tension value of 29 mN/m and an interfacial tension value of 4.5 mN/m against hexadecane. The critical micelle concentration of the crude biosurfactants was 17 mg/L. Addition of NaCl to the aqueous solution of the crude product caused lowering of surface tension at both the aqueous solution-air and aqueous solution-n-hexadecane interfaces. These results indicate that the biosurfactants obtained have potential environmental and industrial applications and may have uses in microbially enhanced oil recovery.     

Colloidal Characteristics,Drug Encapsulation,and Oil-in-Water Emulsion of Dodecenyl-Modified Alginate

Sodium alginate was hydrophobically modified with dodecenyl succinic anhydride in a neutral aqueous solution (pH = 6.8) at room temperature, forming an environmentally friendly amphiphile dodecenyl-modified alginate (DMA). Surface activity of DMA was assessed using surface tension and zeta-potential measurements. Hydrophobic compound-loading capacity as well as oil-in-water emulsion stability of DMA solutions were investigated to study the potential applications of DMA. The critical micelle concentration (CMC) of DMA aqueous solution was found to be 0.70 mg mL⁻¹ with the surface tension being around 33.0 mN m⁻¹. DMA solutions were able to solubilize hydrophobic compounds like Sudan IV and Clofazimine in aqueous medium. 10% peanut oil-in-water emulsions stabilized by 10 mg mL⁻¹ DMA presented good stability during 7 days of storage and the interfacial tension between water and oil was lowered from 23.0 to 9.0 mN m⁻¹. Results showed that DMA was an efficient surfactant and could work as a drug-delivery vehicle or a natural food emulsion stabilizer in the future.