**2. Classification, properties and functional mechanisms of microbial surfaceactive compounds**

Microbial surface-active compounds are a range of structurally diverse molecules produced by different microorganisms and are mostly therefore classified by their structural features, the producing organism and their molecular mass. Their hydrophilic moiety is mainly comprised of an acid, peptide cations, or anions, mono-, di- or polysaccharides while their hydrophobic moiety can be an unsaturated or saturated hydrocarbon chains or fatty acids. The structural orientation on the surfaces and inter phases confers the range of properties, such as the ability to lower surface and interfacial tension of liquids and the formation of micelles and microemulsions between these different phases (Chen et al., 2010a, 2010b).
