Potential applications of microbial surfactants in biomedical sciences

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Abstract

The main commercial use of biosurfactants is in pollution remediation because of their ability to stabilize emulsions. This enhances the solubility and availability of hydrophobic pollutants, thus increasing their potential for biodegradation. One useful property of many biosurfactants that has not been reviewed extensively is their antimicrobial activity. Several biosurfactants have strong antibacterial, antifungal and antiviral activity. Other medically relevant uses of biosurfactants include their role as anti-adhesive agents to pathogens, making them useful for treating many diseases and as therapeutic and probiotic agents. Here, we discuss some of the new and exciting applications and related developments of various microbial surfactants in the field of biomedical sciences.

Section snippets

Iturin group of biosurfactants

One of the earliest noted antimicrobial activities of biosurfactants was that of iturin A, a potent antifungal lipopeptide produced by strains of Bacillus subtilis [9]. In yeast cells, iturin A disrupts the plasma membrane by the formation of small vesicles and the aggregation of intramembranous particles. It also releases electrolytes and high molecular mass products, and degrades phospholipids [10]. Iturin A dramatically increases the electrical conductance of biomolecular lipid membranes,

Surfactin group of biosurfactants

Surfactin, a cyclic lipopeptide produced by B. subtilis strains, is one of the other biosurfactants with well-known antimicrobial properties. There are three different types of surfactins, A, B and C, which are classified according to the differences in their amino acid sequences. Surfactin-A has l-leucine, surfactin-B has l-valine and surfactin-C has l-isoleucine at the amino acid position involved in lactone ring formation with the C14–C15 β-hydroxy fatty acid. Apart from antifungal and

Mannosylerythritol lipids

Members of the Candida antarctica strain produce two kinds of mannosylerythritol lipids (MEL-A and MEL-B) that exhibit antimicrobial activity, particularly against Gram-positive bacteria [22]. MEL-A is one of the most useful biosurfactants examined to date. Isoda et al. [23] investigated the biological activities of seven biosurfactants (MEL-A, MEL-B, polyol lipid, rhamnolipid, sophorose lipid and the succinoyl trehalose lipids STL1 and STL3). All glycolipids, except for rhamnolipid, induce

Other biosurfactants with biological activity

A complex of acylpeptide antibiotics, pumilacidin A, B, C, D, E, F and G was isolated from strains of Bacillus pumilis [27]. Pumilacidin exhibited antiviral activity against HSV-1, inhibitory activity against H+, K+-ATPase, and was found to be protective against gastric ulcers. A new antibiotic from Pseudomonas fluorescens, with biosurfactant properties different from those of the known biosurfactant viscosin from the same species, was later identified and named viscosinamide, which was also

Biosurfactants as anti-adhesives

Swarming motility and biofilm formation are the key actions in the colonization of a surface by bacteria, and increase the likelihood of nosocomial infections. Biosurfactants have been found to inhibit the adhesion of pathogenic organisms to solid surfaces or to infection sites. Surfactin decreases the amount of biofilm formed by Salmonella typhimurium, Salmonella enterica, Escherichia coli and Proteus mirabilis in polyvinyl chloride wells, as well as in vinyl urethral catheters [31].

Other biomedical and therapeutic applications

To generate conventional or monoclonal antibodies for the serological detection of drugs, antibodies, toxins and other low molecular mass substances, a suitable and effective adjuvant is needed. Mittenbuhler et al. [38] showed that bacterial lipopeptides constitute potent nontoxic and nonpyrogenic immunological adjuvants when mixed with conventional antigens. The synthetic lipopeptide N-palmitoyl-S-[2,3-bis(palmitoyloxy)-(2R,S)-propyl-]-(R)-cysteinyl-serine (P3CS) coupled to a Th-cell epitope

Concluding remarks

Biosurfactants have potent antimicrobial applications including antifungal, antibacterial, antimycoplasmal and antiviral activities. They have been used for gene transfection, as ligands for binding immunoglobulins, as adjuvants for antigens and also as inhibitors for fibrin clot formation and activators of fibrin clot lysis. Their ability to alter properties of molecules such as cAMP and PLA2 might lead to their use as modulators of signal transduction. Genetic alteration of biosurfactant

Acknowledgements

We thank the Director of the Institute of Microbial Technology (IMTECH) for providing facilities for our work (IMTECH communication number 033/2003). We are grateful for the assistance of Neena Mehta.

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