Biosurfactant

Biosurfactants are surface-active substances synthesised by living cells. They have the properties of reducing surface tension, stabilising emulsions, promoting foaming and are generally non-toxic and biodegradable. Interest in microbial surfactants has been steadily increasing in recent years due to their diversity, environmentally friendly nature, possibility of large-scale production, selectivity, performance under extreme conditions and potential applications in environmental protection [1, 2]. The use of chemicals for the treatment of a hydrocarbon polluted site may contaminate the environment with their by-products, whereas biological treatment may efficiently destroy pollutants, while being biodegradable themselves. Biosurfactants enhance the emulsification of hydrocarbons, have the potential to solubilise hydrocarbon contaminants and increase their availability for microbial degradation. Hence, biosurfactant producing microorganisms may play an important role in the accelerated bioremediation of hydrocarbon contaminated sites [3−5]. These compounds can also be used in enhanced oil recovery and may be considered for other potential applications in environmental protection [5, 6]. Other applications include herbicides and pesticides formulations, detergents, health care and cosmetics, pulp and paper, coal, textiles, ceramic processing and food industries, uranium ore-processing and mechanical dewatering of peat [1, 2, 7]. Several microorganisms are known to synthesise surface-active agents, most of them are bacteria and yeasts [8, 9]. When grown on hydrocarbon substrate as the carbon source, these microorganisms synthesise a wide range of chemicals with surface activity, such as glycolipid, phospholipid and others [10, 11]. These chemicals are apparently synthesised to emulsify the hydrocarbon substrate and facilitate its transport into the cells.

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References

[1] BANAT, I. M., MAKKAR, R. S., CAMEOTRA, S. S.: Potential commercial applications of microbial surfactants. Appl. Microbiol. Biotechnol. 53 (2000), 495−508.

[2] RAHMAN, K. S. M., THAHIRA-RAHMAN, J., MCCLEAN, S., MARCHANT, R., BANAT, I.M.: Rhamnolipid biosurfactants production by strains of Pseudomonas aeruginosa using low cost raw materials. Biotechnol Prog. 18 (2002), 1277−1281.

[3] ROSENBERG, E., RON, E. Z.: High and low molecular mass microbial surfactants. Appl. Microbiol. Biotechnol. 52 (1999), 154−162.

[4] DEL ‘ARCO, J. P., DE FRANCA, F. P.: Influence of oil contamination levels on hydrocarbon biodegradation in sandy sediments. Environ. Pollut. 110 (2001), 515−519.

[5] RAHMAN, K. S. M., BANAT, I.M., THAHIRA-RAHMAN, J., THAYUMANAVAN, T., LAKSHMANAPERUMALSAMY, P.: Bioremediation of gasoline contaminated soil by a bacterial consortium amended with poultry litter, coir pith and rhamnolipid biosurfactant. Bioresource Technol. 81 (2002), 25−32.

[6] SHULGA, A., KARPENKO, E., VILDANOVA-MARTSISHIN, R., TUROVSKY, A., SOLTYS, M.: Biosurfactant enhanced remediation of oil-contaminated environments. Adsorpt. Sci. Technol. 18 (1999), 171−176.

[7] RON, E. Z., ROSENBERG, E.: Natural roles of biosurfactants. Environ. Microbiol. 3 (2001), 229−236.

[8] BANAT, I. M.: Biosurfactants production and possible uses in microbial enhanced oil recovery and oil pollution remediation: a review. Bioresource Technol. 51 (1995), 1−12.

[9] KIM, S.E., LIM, E. J., LEE, S.O., LEE , J. D., LEE, T.H.: Purification and characterisation of biosurfactants from Nocardia sp. L-417. Biotechnol. Appl. Biochem. 31 (2000), 249−253.

[10] MURIEL, J.M., BRUQUE, J.M., OLIAS, J.M., SANCHEZ, A. J.: Production of biosurfactants by Cladosporium resinae. Biotechnol. Lett. 18 (1996), 235−240.

[11] DESAI, J.D., BANAT, I.M.: Microbial production of surfactants and their commercial potential. Microbiol. Mol. Biol. Rev. 61 (1997), 47−64.