**3. Biomedical applications of microbial surface-active compounds**

The use and potential commercial applications of biosurfactants in the medical field have increased during the past decade. Their antibacterial, antifungal and antiviral activities make them relevant molecules for applications in combating many diseases and as therapeutic agents. Furthermore, biosurfactants are generally considered safer than synthetic pharmaceuticals, due to their biological origin. Their pertinence in these fields is related to their biological properties such as the ability to disrupt membranes leading to cell lysis and metabolite leakage through increased membrane permeability and hence antimicrobial activity. Moreover, similarly to organic-conditioning films, their ability to partition at the interfaces can affect the adhesion properties of cells/microorganisms. Biomedical applications of biosurfactants have been thoroughly described (Banat et al., 2010; Cameotra & Makkar, 2004; Rodrigues et al., 2006a; Rodrigues & Teixeira, 2010; Seydlová & Svobodová, 2008; Singh & Cameotra, 2004).

### **3.1 Antimicrobial activity of biosurfactants**

The search for new antimicrobial drugs remains a major concern nowadays because of the newly emerged pathogenic microorganisms and traditional others which have become virtually unresponsive to existing antibiotics. In fact, no novel or effective chemical antibiotics have been discovered during the last few decades (Hancock & Chapelle, 1999). Microbial metabolites have been recognized as a major source of compounds endowed with ingenious structures and potent biological activities (Donadio et al., 2002). Among these, some biosurfactants have been reported to be suitable alternatives to synthetic medicines and antimicrobial agents and may therefore be used as effective and safe therapeutic agents (Banat et al., 2000; Cameotra & Makkar, 2004; Singh & Cameotra, 2004).
