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The rapid development of biotechnology and the increase in environmental awareness among producers and consumers have placed biological products in a preferential position on the market. The physiochemical properties of biosurfactants make these natural compounds an attractive option with potential use in a variety of industrial and biotechnological applications as additives in foods, cosmetics and detergents. Thus, the aim of the present study was to select the better biosurfactant-producing microorganism between two species of Candida (C. guilliermondii UCP0992 and C. lipolytica UCP0998) grown in media with different sources of carbon (glucose, sugarcane molasses and waste frying oil) and nitrogen (yeast extract, urea and corn steep liquor). After the selection of the microorganism and production medium and biosurfactant production were analyzed. The properties of the biopolymer were then studied in terms of toxicity, using the brine shrimp Artemia salina, vegetable seeds and onion (Allium cepa) as bioindicators. Gas chromatography was performed for the structural characterization of the biomolecule and the determination of its physicochemical composition. Candida guilliermodii grown in a medium with 5.0% molasses, 5.0% corn steep liquor and 5.0% waste frying oil was selected for the production of biosurfactant, with a reduction in surface tension to 28.6 mN/m, a yield of 21 g/l and a critical micelle concentration of 0.7 g/l. The isolated biosurfactant was not toxic to Artemia salina, or the vegetable seeds tested. The biosurfactant had a glycolipid nature. Based on the present results, the novel biosurfactant produced herein has potential application in industrys.

Environmental pollution caused by petroleum and its derivatives, such as diesel fuel, heavy oil, fuel residues, mineral oil and engine oil, is an issue of importance regarding both economic development and ecological restoration. Considerable amounts of petroleum products contaminate groundwater and soil as a consequence of leaks and spills from petroleum refinery processes, oil transportation and storage tanks. While contamination is caused by accidents in some cases, it is often the result of negligent disposal. Biosurfactants have received considerable attention in the field of environmental remediation processes. These substances influence such processes due to their efficacy as dispersion and remediation agents as well as their environmentally friendly characteristics, such as low toxicity and high biodegradability. Thus, this study investigated the potential application of a biosurfactant for enhanced removal capability of motor oil from contaminated sand and water, under laboratory conditions. The biosurfactant was produced by the yeast Candida sphaerica grown in distilled water supplemented with 9% ground nut oil refinery residue and 9% of corn steep liquor were used with their producer microorganism in the remediation of motor oil contained in sand and sea water. Sand oil bioremediation experiments were carried out for 90 days, while in sea water the period was 30 days. The results showed that the addition of the biosurfactant increased the degradation of the oil in the sand to 90%. With regard to the removal of oil on seawater, it was observed that removal percentages were around 85%. In this way, the biosurfactants produced, besides being obtained from low cost substrates, demonstrated efficiency in the removal of oils in sand and water, allowing the substitution of chemical treatment agents by environmental friendly agents.

Biosurfactants are amphipathic molecules with hydrophobic and hydrophilic moieties, which can be obtained by bacteria, yeasts and filamentous fungi. In recent years, the scientific production with a focus on obtaining these bioproducts from industrial waste has increased. This alternative stems from the need to reduce production costs, since biosurfactants are not yet economically competitive against synthetic surfactants, which are petroleum-based, toxic and not biodegradable. Among the properties of biosurfactants we can cite the surface tension reduction, low toxicity, biodegradability, diversity, specificity, dispersing ability, emulsifying, demulsifying, antimicrobial and antioxidant activities. Such properties make biosurfactants attractive for application in several areas. In this sense, the present study evaluated the emulsifying and antioxidant capacity of the biosurfactant produced from low cost substrates by Candida bombicola URM 3718. The emulsifying capacity of the biosurfactant against vegetable oils was compared with guar gum, a vegetable origin emulsifier of common use in the food industry. The total antioxidant capacity (TAC) of the biomolecule was evaluated by the phosphomolybdenum method, seeking the reduction of molybdenum VI in molybdenum V by the antioxidant substance. According to the results, it was possible to verify that the biosurfactant presented excellent emulsification rates when compared to guar gum. The variation of the biosurfactant concentration had little effect on the results. On the other hand, in the results obtained for the antioxidant activity, it was verified that the increase of the concentration of the biosurfactant contributes to the increase of the percentage of TAC. Thus, it can be concluded that the biosurfactant obtained from low-cost substrates has potential for application in food systems, where emulsification and the introduction of antioxidants are extremely important for the useful life of food.

In this study, a new formulation of low-cost, biodegradable, and non-toxic biosurfactant by Candida sphaerica UCP 0995 was investigated. The study was conducted in a bioreactor on an industrial waste-based medium, and a central composite rotatable design was used for optimization. The best results, namely a 25.22 mN/m reduction in surface tension, a biosurfactant yield of 10.0 g/L, and a critical micelle concentration of 0.2 g/L, were achieved in 132 h at an agitation speed of 175 rpm and an aeration rate of 1.5 vvm. Compositional and spectroscopic analyses of the purified biosurfactant by chemical methods, Fourier transform infrared spectroscopy, and nuclear magnetic resonance suggested that it is a glycolipid-type biosurfactant, and it showed no cytotoxicity in the MTT assay. The biosurfactant, submitted to different formulation methods as a commercial additive, remained stable for 120 days at room temperature. Tensioactive properties and stability were evaluated at different pH values, temperatures, and salt concentrations. The biosurfactant obtained with all formulation methods demonstrated good stability, with tolerance to wide ranges of pH, temperature and salinity, enabling application under extreme environmental conditions. Bioremediation tests were performed to check the efficacy of the isolated biosurfactant and the selected microbial species in removing oil from soil. The results demonstrated that the biosurfactant produced has promising properties as an agent for the bioremediation of contaminated soil.