Oil spills: impacts and perspectives of treatment technologies with focus on the use of green surfactants.

Oil spills into the oceans cause irreparable damage to marine life and harms the coastal population of the affected areas. The main measures to be taken in response to an oil spill are to reduce the impact on marine life, prevent oil from reaching the shore through its recovery, and accelerate the degradation of unrecovered oil. Any environmental damage can be reduced if the spilled oil is removed from the water quickly and efficiently. Therefore, it is essential to know the treatment strategies for spilled oils. Several technologies are currently available, including booms, skimmers, in situ burning, use of adsorbents, dispersants/surfactants, and bioremediation. The selection of the type of treatment will depend not only on the effectiveness of the technique, but mainly on the type of oil, amount spilled, location, weather, and sea conditions. In this review, the characteristics of oil spills, their origin, destination, and impacts caused, including major accidents around the world, are initially addressed. Then, the main physical, chemical, and biological treatment technologies are presented, describing their advances, advantages, and drawbacks, with a focus on the use of green surfactants. These agents will be described in detail, showing the evolution of research, recent studies, patents, and commercialized products. Finally, the challenges that remain due to spills, the necessary actions, and the prospects for the development of existing treatment technologies are discussed, which must be linked to the use of combined techniques.

The potential application of biosurfactant produced by Pseudomonas aeruginosa TGC01 using crude glycerol on the enzymatic hydrolysis of lignocellulosic material.

The production of biosurfactant by Pseudomonas aeruginosa TGC01 using crude glycerol and sodium nitrate as the sole substrate and nitrogen source, respectively, was investigated using two mineral culture media. Two inoculum sizes (5 and 10% v/v) and two volumes of the culture medium (50 and 100 mL) in 500 mL Erlenmeyer flask also were used. Enzymatic hydrolyses of waste office paper (WOP), newspaper (NP) and eucalyptus wood chips (EWC) were carried out using the biosurfactant from P. aeruginosa TGC01. The decrease in volume of the culture medium increased the production of rhamnolipid by 500% in relation to concentration obtained when higher volume of culture medium was used. High quantity biosurfactant was recovered (11 g/L) with desired surface active properties after extraction using chloroform:methanol (v/v). The biosurfactant was able to reduce the water surface tension from 72 to 27 mN/m with a critical micelle concentration (CMC) of 100 mg/L and a stable emulsion index (above 60%) in the enzymatic hydrolysis (pH 4.8 and 50 °C for 4 h). Biosurfactant increased the glucose released in the enzymatic hydrolysis in relation to control (without tensoactive) when WOP (19% increase) and NP (113% increase) were used. The process for NP (18% lignin) was economical, given that the biosurfactant present made a delignification process unnecessary.

Treatment of oily effluent using a low-cost biosurfactant in a flotation system.

Fuel and lubricating oil leaks produce an oily wastewater that creates an environmental problem for industries. Dissolved air flotation (DAF) has been successfully employed for the separation of oily contaminants. Collectors constitute an auxiliary tool in the DAF process that enhances the separation efficiency by facilitating the adhesion of the contaminant particles. The use of biosurfactants as collectors is a promising technology in flotation processes, as these biomolecules are biodegradable and non-toxic. In the present study, a biosurfactant was produced from the bacteria Pseudomonas aeruginosa UCP 0992 cultivated in 0.5% corn steep liquor and 4.0% vegetable oil residue in a bioreactor at 225 rpm for 120 h, resulting in a surface tension of 26.5 mN/m and a yield of 26 g/L. The biosurfactant demonstrated stability when exposed to different temperatures, heating times, pH values and salt and was characterised as a glycolipid with a critical micelle concentration of 600 mg/L. A central composite rotatable design was used to evaluate the effect of the crude biosurfactant added to a laboratory DAF prototype on the removal efficiency of motor oil. The isolated and formulated forms of the biosurfactant were also tested in the prototype after the optimisation of the operational conditions. The results demonstrated that all forms of the biosurfactant increased the oil separation efficiency of the DAF process by 65 to 95%. In conclusion, the use of biosurfactants is a promising alternative as an auxiliary tool in flotation processes for the treatment of oily waters generated by industrial activities.

Application of a low-cost biosurfactant in heavy metal remediation processes.

The industrial interest in microbial surfactants has intensified in recent years due to the characteristics of these compounds, such as biodegradability, low toxicity, and effectiveness in removing heavy metals and hydrophobic organic compounds from soil and water. This paper describes the production of a biosurfactant by the yeast Candida tropicalis grown in distilled water with 2.5% molasses, 2.5% frying oil and 4% corn steep liquor. The production of the biosurfactant reached 27 g/l in a 50-l bioreactor with a surface tension of 30 mN/m. Surface tension and engine oil emulsification assays demonstrated the stability of biosurfactant under extreme conditions of temperature and pH as well as in the presence of NaCl. Chemical structures of the biosurfactant were identified using GC-MS and NMR. The isolated biosurfactant was characterised as an anionic molecule capable of reducing the surface tension of water from 70 to 30 mN/m at 0.5% of the critical micelle concentration, with no toxic effects on plant seeds or brine shrimp. In tests involving both the crude and isolated biosurfactant for the removal of heavy metals from contaminated sand under dynamic conditions, the removal rates for Zn and Cu ranged from 30 to 80%, while the best removal rate for Pb was 15%. Tests in packed columns also confirmed the ability of biosurfactant to remove Cu and Zn at rates ranging from 45 to 65%. However, lead was not removed under static conditions. The removal kinetics demonstrated that 30 min was sufficient for the removal of metals and a single washing with the biosurfactant achieved greater removal efficiency. The use of the biosurfactant led to a significant reduction in the electrical conductivity of solutions containing heavy metals. The present findings as well as a brief economic analysis suggest the great potential of this agent for industrial remediation processes of soil and water polluted with inorganic contaminants.

Production of a biosurfactant from Bacillus methylotrophicus UCP1616 for use in the bioremediation of oil-contaminated environments.

The aim of the present study was to produce a microbial biosurfactant for use in the bioremediation of environments contaminated with petroleum products. Bacillus methylotrophicus was isolated from seawater taken from a port area and cultivated using industrial waste as substrate (corn steep liquor and sugarcane molasses [both at 3%]). Surface tension measurements and motor oil emulsification capacity were used for the evaluation of the production of the biosurfactant, which demonstrated stability in a broad range of pH and temperature as well as a high concentration of saline, with the reduction of the surface tension of water to 29 mN/m. The maximum concentration of biosurfactant (10.0 g/l) was reached after 144 h of cultivation. The biosurfactant was considered to be a lipopeptide based on the results of proton nuclear magnetic resonance and Fourier transformed infrared spectroscopy. The tests demonstrated that the biosurfactant is innocuous and has potential for the bioremediation of soil and water contaminated by petroleum products. Thus, the biosurfactant described herein has a low production cost and can be used in environmental processes.

Use of bacterial biosurfactants as natural collectors in the dissolved air flotation process for the treatment of oily industrial effluent.

The aim of the present study was to investigate the separation of oil from water using a bench-scale DAF prototype with the addition of biosurfactants isolated from Pseudomonas cepacia CCT6659 and Bacillus cereus UCP1615. The best operating conditions for the DAF prototype were determined using a central composite rotatable design. The results demonstrated that the biosurfactants from P. cepacia and B. cereus increased the oil separation efficiency from 53.74% (using only microbubbles) to 94.11 and 80.01%, respectively. The prediction models for both DAF-biosurfactant systems were validated, showing an increase in the efficiency of the DAF process from 53.74% to 98.55 and 70.87% using the formulated biosurfactants from P. cepacia and B. cereus, respectively. The biosurfactant from P. cepacia was selected as the more promising product and used for the treatment of oily effluent from a thermoelectric plant, achieving removal rates ranging between 75.74 (isolated biosurfactant) and 95.70% (formulated biosurfactant), respectively.

Production of Biosurfactants by Pseudomonas Species for Application in the Petroleum Industry.

The production of surfactants by microorganisms has become an attractive option in the treatment of oil-contaminated environments because biosurfactants are biodegradable and less toxic than synthetic surfactants, although production costs remain high. With the aim of reducing the cost of biosurfactant production, three strains of Pseudomonas (designated P1, P2, and P3) were cultivated in a low-cost medium containing molasses and corn steep liquor as substrates. Following the selection of the best producer (P3), a rotational central composite design (RCCD) was used to determine the influence of substrates concentration on surface tension and biosurfactant yield. The biosurfactant reduced the surface tension of water to 27.5 mN/m, and its CMC was determined to be 600 mg/L. The yield was 4.0 g/L. The biosurfactant demonstrated applicability under specific environmental conditions and was able to remove 80 to 90% of motor oil adsorbed to sand. The properties of the biosurfactant suggest its potential application in bioremediation of hydrophobic pollutants.

Biosurfactants: Multifunctional Biomolecules of the 21st Century.

In the era of global industrialisation, the exploration of natural resources has served as a source of experimentation for science and advanced technologies, giving rise to the manufacturing of products with high aggregate value in the world market, such as biosurfactants. Biosurfactants are amphiphilic microbial molecules with hydrophilic and hydrophobic moieties that partition at liquid/liquid, liquid/gas or liquid/solid interfaces. Such characteristics allow these biomolecules to play a key role in emulsification, foam formation, detergency and dispersal, which are desirable qualities in different industries. Biosurfactant production is considered one of the key technologies for development in the 21st century. Besides exerting a strong positive impact on the main global problems, biosurfactant production has considerable importance to the implantation of sustainable industrial processes, such as the use of renewable resources and "green" products. Biodegradability and low toxicity have led to the intensification of scientific studies on a wide range of industrial applications for biosurfactants in the field of bioremediation as well as the petroleum, food processing, health, chemical, agricultural and cosmetic industries. In this paper, we offer an extensive review regarding knowledge accumulated over the years and advances achieved in the incorporation of biomolecules in different industries.

Synthesis and Characterization of Silver Nanoparticles Stabilized with Biosurfactant and Application as an Antimicrobial Agent.

Surfactants can be used as nanoparticle stabilizing agents. However, since synthetic surfactants are not economically viable and environmentally friendly, biosurfactants are emerging as a green alternative for the synthesis and stabilization of nanoparticles. Nanoparticles have been applied in several areas of industry, such as the production of biomedical and therapeutic components, packaging coating, solar energy generation and transmission and distribution of electrical energy, among others. The aim of this study was to synthesize, in a simple and green way, silver nanoparticles (AgNPs) using the biosurfactant produced by Candida lipolytica UCP 0899 as a stabilizer. AgNPs were examined and morphologically characterized using the techniques of ultraviolet-visible spectroscopy (UV-visible), scanning electron microscopy (SEM), zeta potential and energy dispersive X-ray spectroscopy (EDS). Newly formed silver nanoparticles showed a maximum UV-visible absorption peak at 400 nm, while a shift to 410 nm was observed in those stored for 120 days. SEM micrograph confirmed the formation of nanoparticles with an average size of 20 nm and with a predominant spherical structure, while a zeta potential of -60 mV suggested that the use of the biosurfactant promoted their stability. Stabilized nanoparticles were tested for their antimicrobial activity against bacterial isolates of Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli and Enterobacter sp., as well as fungal isolates of Candida albicans and Aspergillus niger. At a concentration of 16.50 µg/mL, AgNPs inhibited the growth of all target microorganisms according to the following decreasing order: E. coli (95%), S. aureus, C. albicans (90%), A. niger (85%), Enterobacter sp. (75%) and P. aeruginosa (71%). These results suggest the potential use of the biosurfactant as a stabilizer of silver nanoparticles as an antimicrobial agent in different industrial sectors. Furthermore, the in vivo toxicity potential of biosurfactants was evaluated using the Tenebrio molitor model. The larvae were treated with concentrations in the range of 2.5, 5.0 and 10 g/L, and no mortality was observed within the 24 to 72 h period, demonstrating non-toxicity within the tested concentration range. These findings support the safety, efficacy and non-toxicity of biosurfactant-stabilized nanoparticles.

Microbial Biosurfactant: Candida bombicola as a Potential Remediator of Environments Contaminated by Heavy Metals.

Industrial interest in surfactants of microbial origin has intensified recently due to the characteristics of these compounds, such as biodegradability and reduced toxicity, and their efficiency in removing heavy metals and hydrophobic organic compounds from soils and waters. The aim of this study was to produce a biosurfactant using Candida bombicola URM 3712 in a low-cost medium containing 5.0% molasses, 3.0% corn steep liquor and 2.5% residual frying oil for 144 h at 200 rmp. Measurements of engine oil tension and emulsification were made under extreme conditions of temperature (0 °C, 5 °C, 70 °C, 100 °C and 120 °C), pH (2-12) and NaCl concentrations (2-12), demonstrating the stability of the biosurfactant. The isolated biosurfactant was characterized as an anionic molecule with the ability to reduce the surface tension of water from 72 to 29 mN/m, with a critical micellar concentration of 0.5%. The biosurfactant had no toxic effect on vegetable seeds or on Eisenia fetida as a bioindicator. Applications in the removal of heavy metals from contaminated soils under dynamic conditions demonstrated the potential of the crude and isolated biosurfactant in the removal of Fe, Zn and Pb with percentages between 70 and 88%, with the highest removal of Pb being 48%. The highest percentage of removal was obtained using the cell-free metabolic liquid, which was able to remove 48, 71 and 88% of lead, zinc and iron from the soil, respectively. Tests in packed columns also confirmed the biosurfactant's ability to remove Fe, Zn and Pb between 40 and 65%. The removal kinetics demonstrated an increasing percentage, reaching removal of 50, 70 and 85% for Pb, Zn and Fe, respectively, reaching a greater removal efficiency at the end of 24 h. The biosurfactant was also able to significantly reduce the electrical conductivity of solutions containing heavy metals. The biosurfactant produced by Candida bombicola has potential as an adjuvant in industrial processes for remediating soils and effluents polluted by inorganic contaminants.

Evaluation antimicrobial and antiadhesive properties of the biosurfactant Lunasan produced by Candida sphaerica UCP 0995.

Different groups of biosurfactants exhibit diverse properties and display a variety of physiological functions in producer microorganisms; these include enhancing the solubility of hydrophobic/water-insoluble compound, heave metal binding, bacterial pathogenesis, cell adhesion and aggregation, quorum sensing and biofilm formation. Candida sphaerica was grown in a low cost medium, consisting of distilled water supplemented with 9% refinery residue of soybean oil and 9% corn steep liquor, for 144 h at 28°C and 150 rpm. The cell-free supernatant obtained at the end of the experiments was submitted to extraction, and afterward the biosurfactant was isolated using methanol with a yield of 9 g l(-1). The critical micelle concentration of the biosurfactant was found to be 0.25 mg ml(-1) with a surface tension of 25 mN m(-1). Several concentrations of the biosurfactant (0.625-10 mg ml(-1)) were used to evaluate its antimicrobial and antiadhesive activities against a variety of microorganisms. The biosurfactant showed antimicrobial activity against Streptococcus oralis (68%), Candida albicans (57%), and Staphylococcus epidermidis(57.6%) for the highest concentration tested. Furthermore, the biosurfactant at a concentration of 10 mg ml(-1) inhibited the adhesion between 80 and 92% of Pseudomonas aeruginosa, Streptococcus agalactiae, Streptococcus sanguis12. Inhibition of adhesion with percentages near 100% occurred for the higher concentrations of biosurfactant used. Results gathered in this study point to a potential use of the biosurfactant in biomedical applications.

Economic optimized medium for tensio-active agent production by Candida sphaerica UCP0995 and application in the removal of hydrophobic contaminant from sand.

Statistical experimental designs and response surface methodology were employed to optimize the concentrations of agroindustrial residues as soybean oil (SORR) from refinery, and corn steep liquor (CSL) from corn industry, for tensio-active agent produced by Candida sphaerica UCP 0995. Three 2(2) full factorial design were applied sequentially to investigate the effects of the concentrations and interactions of soybean oil refinery residue and corn steep liquor on the surface tension of free-cell culture broth for 144 h. Two 2(2) central composite designs and response surface methodology were adopted to derive a statistical model to measure the effect of SORR and CSL on the surface tension of the free-cell culture broth for 144 h. The regression equation obtained from the experimental data using a central composite design was solved, and by analyzing the response surface contour plots, the optimal concentrations of the constituents of the medium were determined: 8.63% v/v (≅9% v/v) of SORR and 8.80% v/v (≅9% v/v) CSL. The minimum surface tension predicted and experimentally confirmed was 25.25 mN/m. The new biosurfactant, denominated Lunasan, recovered 95% of motor oil adsorbed in a sand sample, thus showing great potential for use in bioremediation processes, especially in the petroleum industry.

Removal of heavy oil from contaminated surfaces with a detergent formulation containing biosurfactants produced by Pseudomonas spp.

Industrial plants powered by heavy oil routinely experience problems with leaks in different parts of the system, such as during oil transport, the lubrication of equipment and mechanical failures. The surfactants, degreasing agents and solvents that make up detergents commonly used for cleaning grease-covered surfaces are synthetic, non-biodegradable and toxic, posing risks to the environment as well as the health of workers involved in the cleaning process. To address this problem, surfactant agents of a biodegradable nature and low toxicity, such as microbial surfactants, have been widely studied as an attractive, efficient solution to replace chemical surfactants in decontamination processes. In this work, the bacterial strains Pseudomonas cepacia CCT 6659, Pseudomonas aeruginosa UCP 0992, Pseudomonas aeruginosa ATCC 9027 and Pseudomonas aeruginosa ATCC 10145 were evaluated as biosurfactant producers in media containing different combinations and types of substrates and under different culture conditions. The biosurfactant produced by P. aeruginosa ATCC 10145 cultivated in a mineral medium composed of 5.0% glycerol and 2.0% glucose for 96 h was selected to formulate a biodetergent capable of removing heavy oil. The biosurfactant was able to reduce the surface tension of the medium to 26.40 mN/m, with a yield of approximately 12.00 g/L and a critical micelle concentration of 60.00 mg/L. The biosurfactant emulsified 97.40% and dispersed 98.00% of the motor oil. The detergent formulated with the biosurfactant also exhibited low toxicity in tests involving the microcrustacean Artemia salina and seeds of the vegetable Brassica oleracea. The detergent was compared to commercial formulations and removed 100% of the Special B1 Fuel Oil (OCB1) from different contaminated surfaces, demonstrating potential as a novel green remover with industrial applications.

Biosorption of heavy fuel oil from aqueous solution by Eichhornia crassipes (Mart.) Solms in natura.

This work investigated the efficiency of bioremediation of heavy fuel oil (HFO) in aqueous solutions by living Eichhornia crassipes (Mart.) Solms, also known as water hyacinth. Possibility of using post-biosorption macrophytes to produce briquettes was also studied. HFO was characterized by its density, viscosity, and Fourier-transform infrared spectroscopy. Water hyacinth was characterized by scanning electron microscope, pH of zero point of charge, buoyancy, and wettability. Experiments were performed to evaluate effects of contact time and initial oil concentration on biosorption. E. crassipes presented a hydrophobic nature, ideal for the treatment of oily effluents. Hollow structures in macrophytes were also identified, which favor capillary rise and retention of oils of high density and viscosity. Biosorption efficiency of HFO reached 94.8% in tests with initial concentration of 160 mg.L-1. A calorific value of 4022 kcal.kg-1 was obtained in briquettes made of water hyacinth post-biosorption. These results reinforce the great potential of E. crassipes as a sustainable and efficient alternative for treatment of oily effluents.

Effect of medium components on the production of a biosurfactant from Candida tropicalis applied to the removal of hydrophobic contaminants in soil.

The influence of medium constituents on the production of biosurfactants by Candida tropicalis cultivated in waste frying oil was investigated according to a fractional factorial 2(5-1) design. The combined effect of the C/N(inorganic), C/Fe, C/Mg, and C/P ratios and yeast extract on surface tension reduction, biosurfactant yield, emulsification activity, and biomass were studied. The highest biosurfactant yield was reached when low C/Mg and low C/P ratio variables were combined, while the cell growth was favored by increasing the nitrogen concentration. The highest surface tension net decrease, on the other hand, was observed at low yeast extract concentration, low C/Fe, and high C/P ratios. Emulsification indices against lubrication and automobile waste oil of approximately 65 to 95% were observed. The crude biosurfactant produced in the medium--formulated with 2% waste frying oil, 0.067% NH4Cl, 0.025% MgSO4.7H2O, 0.067% KH2PO4, and 0.0026% FeCl3.6H2O--removed approximately 78 to 97% of the petroleum and motor oil adsorbed in sand samples.

Biosurfactants: Production and application prospects in the food industry.

There has been considerable interest in the use of biosurfactants due to the diversity of structures and the possibility of production from a variety of substrates. The potential for industrial applications has been growing, as these natural compounds are tolerant to common processing methods and can compete with synthetic surfactants with regards to the capacity to reduce surface and interfacial tensions as well as stabilise emulsions while offering the advantages of biodegradability and low toxicity. Among biosurfactant-producing microorganisms, some yeasts present no risks of toxicity or pathogenicity, making them ideal for use in food formulations. Indeed, the use of these biomolecules in foods has attracted industrial interest due to their properties as emulsifiers and stabilizers of emulsions. Studies have also demonstrated other valuable properties, such as antioxidant and antimicrobial activity, enabling the aggregation of greater value to products and the avoidance of contamination both during and after processing. All these characteristics allow biosurfactants to be used as additives and versatile ingredients for the processing of foods. The present review discusses the potential application of biosurfactants as emulsifying agents in food formulations, such as salad dressing, bread, cakes, cookies, and ice cream. The antioxidant, antimicrobial and anti-adhesive properties of these biomolecules are also discussed, demonstrating the need for further studies to make the use of the natural compounds viable in this expanding sector.

Production of cupcake-like dessert containing microbial biosurfactant as an emulsifier.

This work describes the application of the biosurfactant from Candida bombicola URM 3718 as a meal additive like cupcake. The biosurfactant was produced in a culture medium containing 5% sugar cane molasses, 5% residual soybean oil and 3% corn steep liquor. The surface and interfacial tension of the biosurfactant were 30.790 ± 0.04 mN/m and 0.730 ± 0.05 mN/m, respectively. The yield in isolated biosurfactant was 25 ± 1.02 g/L and the CMC was 0.5 g/L. The emulsions of the isolated biosurfactant with vegetable oils showed satisfactory results. The microphotographs of the emulsions showed that increasing the concentration of biosurfactant decreased the oil droplets, increasing the stability of the emulsions. The biosurfactant was incorporated into the cupcake dessert formulation, replacing 50%, 75% and 100% of the vegetable fat in the standard formulation. Thermal analysis showed that the biosurfactant is stable for cooking cupcakes (180 °C). The biosurfactant proved to be promising for application in foods low in antioxidants and did not show cytotoxic potential in the tested cell lines. Cupcakes with biosurfactant incorporated in their dough did not show significant differences in physical and physical-chemical properties after baking when compared to the standard formulation. In this way, the biosurfactant has potential for application in the food industry as an emulsifier for flour dessert.

Studies of the cell surface properties of Candida species and relation to the production of biosurfactants for environmental applications.

In practical bioremediation of petroleum pollution, treatment systems often use soil, sand, and other aquifer porous media besides water solutions. The distribution of the microbial cell also plays an important role in the whole process of bioremediation; therefore, the adhesion ability of cells to porous media is one of the key factors influencing the efficiency of treatment. The probable modes of hydrocarbon uptake in cells of Candida were studied based on data for cell hydrophobicity, emulsifying activity, surface tension, and interfacial tension of the cell-free culture medium. Six Candida strains were cultivated in insoluble and soluble substrates for 144 h, including n-hexadecane, soybean oil, ground-nut oil refinery residue, corn steep liquor, and glucose. The results obtained showed the potential of yeasts for application in the removal of hydrophobic compounds. Depending the strain and substrate used the adhesion ability of yeast cells and the production of surfactants and emulsifiers can take place simultaneously, thus increasing the efficiency of bioremediation treatment of petroleum pollution. The application of crude biosurfactants separated from the yeast cells was also demonstrated by tests of removal of petroleum and the derivate motor oil adsorbed in sand samples. Biosurfactants produced in low-cost medium were able to remove 90% of the hydrophobic contaminants.

Production and formulation of a new low-cost biosurfactant to remediate oil-contaminated seawater.

The aim of the present study was to produce biosurfactants using three bacterial strains (Pseudomonas cepacia CCT6659, Bacillus methylotrophicus UCP 1616 and Bacillus cereus UCP 1615) cultivated in mineral medium containing different carbon (glucose, sucrose, molasses and waste frying oil) and nitrogen [NH4NO3, (NH4)2SO4, peptone, yeast extract and corn steep liquor] sources. B. cereus stood out as the best biosurfactant producer when inoculated with a 1.5% cell suspension and cultivated at 28 °C and 200 rpm in 2.0% molasses and 1.0% corn steep liquor for 48 h. Under these conditions, medium surface tension was reduced to 26.2 ± 0.2 mN/m, and biosurfactant concentration achieved 2.05 ± 0.32 g/L. The biosurfactant showed a critical micelle concentration of 0.90 ± 0.05 g/L, proved to be highly stable in wide ranges of pH, salt concentration and heating temperature, and exerted low toxicity to larvae of Artemia salina as a marine environmental bioindicator. Structural characterisation of biosurfactant suggested a lipopeptide composition. The biotensioactive agent was shown to effectively remove motor oil adsorbed to marine rock (91.0 ± 0.4%) and to disperse it in seawater (70.0 ± 0.4%). The biosurfactant formulated with 0.2% potassium sorbate demonstrated considerable potential for application in the petroleum industry, where it could be successfully used as a commercial product to mobilize oil in marine environments.

Application of biosurfactants and chitosan in toothpaste formulation.

The aim of the present study was to formulate toothpastes containing biosurfactants and either fungal chitosan or sodium fluoride and evaluate the cytotoxicity, antimicrobial action and inhibition potential against biofilm formed by Streptococcus mutans. Chitosan was extracted from the biomass of the fungus Mucorales. We tested biosurfactants produced by Pseudomonas aeruginosa UCP 0992 (PB), Bacillus metylotrophicus UCP 1616 (BB) and Candida bombicola URM 3718 (CB). Fractional inhibitory concentration analysis was performed to determine the type of interaction between the compounds. Six toothpaste were prepared, the active ingredients of which were the biosurfactants, chitosan or sodium fluoride. The cytotoxicity tests were performed using the 3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay for the L929 (mouse fibroblast) and RAW 264.7 (mouse macrophage) cell lines. The toothpastes were tested with regard to pH, consistency and foaming capacity. The inhibition of biofilm was investigated by applying the toothpaste to biofilm formed in modified artificial saliva for 24 h at 37 °C in anaerobiosis. All substances had a minimum inhibitory concentration (MIC) for S. mutans. The combinations of CB and PB with chitosan had an additive effect against S. mutans, whereas BB combined with chitosan had an indifferent effect. The toothpastes were non-toxic. The formulations had pH around 9, spreading capacity between 8 and 17 mm and foaming capacity between 63 and 95%. All formulations inhibited the cellular viability of S. mutans in the biofilm, with similar results compared to the commercial toothpaste tested. The present results show that the formulations suggested are promising when compared to a commercial tooth paste.