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

    Year: 2017

    Journal: AMB Express, Volume 7, NOV 15

    Authors: Rocha e Silva, Fernanda Cristina P.; Roque, Bruno Augusto C.; Rocha e Silva, Nathalia Maria P.; Rufino, Raquel D.; Luna, Juliana M.; Santos, Valdemir A.; Banat, Ibrahim M.; Sarubbo, Leonie A.

    Organizations: Brazilian fostering agency National Council for Scientific and Technological Development (CNPq); Brazilian fostering agency Coordination for the Evaluation and Improvement of Higher Education Personnel (CAPES); Brazilian fostering agency State of Pernambuco Assistance to Science and Technology Foundation (FACEPE); Brazilian fostering agency Candeias Energy Company (CEC); Brazilian fostering agency National Electrical Energy Agency (ANEEL)

    Keywords: Pseudomonas; Bacillus; Candida; Demulsification; Cell hydrophobicity; Interfacial tension; Oil; Environmental contamination

    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.
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