**3.1.3 Anti mycoplasma activity**

Some investigations have shown interesting anti-mycoplasma effects for surfactins. Mycoplasma contamination in cell culture is a frequently occurring serious limitation to biomedical research, particularly when it affects the irreplaceable cell lines which ultimately ends up destroyed. Earlier studies showed that surfactin treatment of mammalian cells that had been contaminated with mycoplasmas permitted specific inactivation of mycoplasmas without significantly damaging effects on cell metabolism in the culture (Vollenbroich et al., 1997b). In a more recent study, surfactin was used to eliminate mycoplasma from an extensively infected irreplaceable hybridoma cell line (Kumar et al., 2007). There were apparent indications of limited elimination, suggesting the possible use of surfactin in achieving total decontamination. However, it was observed that surfactin was toxic to the infected hybridoma cells plated at various cell densities and exposure times, therefore it was suggested that preliminary tests should be carried out to determine the cytotoxicity of surfactin before use in decontamination.

Another study confirmed surfactin potential to eliminate mycoplasma cells independently of the target cell, which is a significant advantage over the mode of action of conventional antibiotics (Fassi et al., 2007). This study also reported that surfactin exhibited a synergistic effect in combination with enrofloxacin, and resulted in mycoplasma-killing activity of about two orders of magnitude greater than when the molecules were used separately.

### **3.1.4 Antifungal activity**

The antifungal activities of biosurfactants have long been known, although their action against human pathogenic fungi has been rarely described (Abalos et al., 2001; Chung et al.,

Antiviral effects have also been reported for surfactin and its analogues (Naruse et al., 1990). More effective inactivation of enveloped viruses, such as retroviruses and herpes viruses, were noted compared to non-enveloped viruses, suggesting that inhibitory action links may be due to physico-chemical interactions with the virus envelope (Vollenbroich et al., 1997a). Antiviral activity of some lipopeptides therefore may take place as a result of the viral lipid envelope and capsid disintegration due to ion channels formation, with consequent loss of the viral proteins involved in virus adsorption and/or penetration (Jung et al., 2000;

*In vitro* experiments showed that both surfactin and fengycin produced by *B. subtilis* fmbj were able to inactivate cell-free virus stocks of porcine parvovirus, pseudorabies virus, newcastle disease virus and bursal disease virus and could effectively inhibit infections and

Sophorolipids are also claimed to have activity against human immunodeficiency virus (Shah et al., 2005) and trehalose lipids (namely trehalose dimycolate, TDM) conferred higher resistance to intranasal infection by influenza virus in mice though inducing proliferation of T-lymphocytes bearing gamma/delta T-cell receptors, associated with the maintenance of acquired resistance to the infection (Hoq et al., 1997, as cited in Franzetti et

Rhamnolipid alginate complex also showed significant antiviral activity against herpes simplex virus types 1 and 2. In particular, they significantly inhibited the herpesvirus cytopathic effect in the Madin-Darby bovine kidney cell line (Remichkova et al., 2008). The suppressive effect of the compounds on herpes simplex virus replication was dosedependent and occurred at concentrations lower than the critical micelle concentration.

Some investigations have shown interesting anti-mycoplasma effects for surfactins. Mycoplasma contamination in cell culture is a frequently occurring serious limitation to biomedical research, particularly when it affects the irreplaceable cell lines which ultimately ends up destroyed. Earlier studies showed that surfactin treatment of mammalian cells that had been contaminated with mycoplasmas permitted specific inactivation of mycoplasmas without significantly damaging effects on cell metabolism in the culture (Vollenbroich et al., 1997b). In a more recent study, surfactin was used to eliminate mycoplasma from an extensively infected irreplaceable hybridoma cell line (Kumar et al., 2007). There were apparent indications of limited elimination, suggesting the possible use of surfactin in achieving total decontamination. However, it was observed that surfactin was toxic to the infected hybridoma cells plated at various cell densities and exposure times, therefore it was suggested that preliminary tests should be carried out to determine the cytotoxicity of

Another study confirmed surfactin potential to eliminate mycoplasma cells independently of the target cell, which is a significant advantage over the mode of action of conventional antibiotics (Fassi et al., 2007). This study also reported that surfactin exhibited a synergistic effect in combination with enrofloxacin, and resulted in mycoplasma-killing activity of about two orders of magnitude greater than when the molecules were used separately.

The antifungal activities of biosurfactants have long been known, although their action against human pathogenic fungi has been rarely described (Abalos et al., 2001; Chung et al.,

**3.1.2 Antiviral activity** 

Seydlová & Svobodová, 2008).

**3.1.3 Anti mycoplasma activity** 

surfactin before use in decontamination.

**3.1.4 Antifungal activity** 

al., 2010b).

replication of these viruses (Huang et al., 2006).

2000; Tanaka et al., 1997). The previously mentioned cellobiose lipid flocculosin isolated from *Pseudozyma flocculosa*, was shown to display *in vitro* antifungal activity against several pathogenic yeasts, associated with human mycoses, including *Candida lusitaniae, Cryptococcus neoformans, Trichosporon asahii* and *Candida albicans* (Mimee et al., 2005). This product positively inhibited all pathogenic strains tested under acidic conditions and showed synergistic activity with amphotericin B. Moreover, no significant cytotoxicity was detected when tested against human cell lines. In nature, flocculosin is part of *P. flocculosa* biocontrol arsenal against other fungi. Recent reports however have suggested that flocculosin is also used by *P. flocculosa* as a nutrient source when experiencing food limitation and the molecule is rapidly deacylated under alkaline conditions losing its antimicrobial activity which may explain conflicting results concerning the antimicrobial activity of this class of glycolipids (Mimee et al., 2009).

Other antifungal activity of biosurfactants against phytopathogenic fungi has also been described. It has been recently demonstrated that glycolipids, such as cellobiose lipids (Kulakovskaya et al., 2009, 2010) and rhamnolipids (Debode et al., 2007, Banat et al, 2010) and cyclic lipopeptides (Tran et al., 2007, 2008, as cited in Banat et al, 2010), including surfactin, iturin and fengycin (Kim et al., 2010; Arguelles-Arias et al., 2009, Chen et al., 2009, Grover et al., 2010, Mohammadipour et al., 2009, Snook et al., 2009) can all have varying degrees of antimicrobial activities.

## **3.2 Antiadhesion activity of biosurfactants**

Microbial biofilms formation on medical and technical equipment is an important and mostly hazardous occurrence, especially as the bacteria within such biofilms usually become highly resistant to antibiotics and adverse environmental challenges. Several approaches have been adopted in order to limit pathogen colonization. Strict hygienic practices by healthcare personnel such as hand washing and regular disinfection of equipment and environment become of grave importance. However, it should be noted that routine disinfection is becoming controversial as frequent application becomes less effective (Dettenkofer et al., 2004, 2007, Kramer et al., 2006, as cited in Falagas & Makris, 2009).
