Yeasts and bacterial biosurfactants as demulsifiers for petroleum derivative in seawater emulsions

Abstract Oil sludge or waste generated in transport, storage or refining forms highly stable mixtures due to the presence and additives with surfactant properties and water forming complex emulsions. Thus, demulsification is necessary to separate this residual oil from the aqueous phase for oil processing and water treatment/disposal. Most used chemical demulsifiers, although effective, are environmental contaminants and do not meet the desired levels of biodegradation. We investigated the application of microbial biosurfactants as potential natural demulsifiers of petroleum derivatives in water emulsions. Biosurfactants crude extracts, produced by yeasts (Candida guilliermondii, Candida lipolytica and Candida sphaerica) and bacteria (Pseudomonas aeruginosa, Pseudomonas cepacia and Bacillus sp.) grown in industrial residues, were tested for demulsification capacity in their crude and pure forms. The best results obtained were for bacterial biosurfactants, which were able to recover about 65% of the seawater emulsified with motor oil compared to 35–40% only for yeasts products. Biosurfactants were also tested with oil-in-water (O/W) and water-in-oil (W/O) kerosene model emulsions. No relationship between interfacial tension, cell hydrophobicity and demulsification ratios was observed with all the biosurfactants tested. Microscopic illustrations of the emulsions in the presence of the biosurfactants showed the aspects of the emulsion and demulsification process. The results obtained demonstrate the potential of these agents as demulsifiers in marine environments

Biosurfactants in improving bioremediation effectiveness in environmental contamination by hydrocarbons

Recent biotechnological advances currently evidence new surfactant production technologies. Biocompounds produced by fermentative processes appeared as an economic and sustainable alternative to many synthetic molecules. Thereby, biosurfactants have become a promising substitute due to their synthesis potential by a wide variety of microorganisms. Biosurfactants are a highly diverse group of structures, such as glycolipids, lipopeptides, polysaccharide-protein complexes, phospholipids, fatty acids, and neutral lipids. This diversity promotes many advantages compared to synthetic surfactants, thus making biosurfactants the most natural choice for technological advances associated with sustainable development. Such advantages include fermentative production viability by using renewable resources, effectiveness in small concentrations even under extreme conditions, selective and specific potential for several applications, lower toxicity, higher biodegradability, and better stability to physicochemical variations. Despite their benefits, biosurfactants are not widely used because of the high production costs. Hence, cost-effective substrates, optimized cultivation conditions, and mutant lineage development are imperative to make these biomolecules an economically competitive product to propose a widespread replacement of synthetic surfactants.College of Agricultural and Technological Sciences São Paulo State University (Unesp)College of Agricultural and Technological Sciences São Paulo State University (Unesp