**3.2.2 Biofilms on food processing surfaces**

In addition to the treatment of biomaterials used for medical devices, biosurfactants have also been used in the pre-treatment of material surfaces found in food-processing environments. Pathogenic bacteria implicated in food-borne illness outbreaks are able to form biofilms on food contact surfaces that are more resistant to sanitation than free-living cells (Kalmokoff et al., 2001; Kim et al., 2006; Stepanovic et al., 2004). The pre-conditioning of surfaces using microbial surface-active compounds may be an interesting strategy for preventing the adhesion of food-borne pathogens to solid surfaces. Meylheuc et al., (2006b) demonstrated that the preconditioning of stainless steel surfaces with an anionic biosurfactant produced by *Pseudomonas fluorescens* reduced the number of *L. monocytogenes* LO28-adhering cells and thus favoured the bactericidal activities of the disinfectants sodium hypochlorite (NaOCl) and peracetic acid/hydrogen peroxide (PAH).

Similarly, biosurfactants obtained from *Lactobacillus helveticus* and *P. fluorescens* were able to inhibit the adhesion of four *Listeria* strains to stainless steel (Meylheuc et al., 2006a). Whichever strain of *L. monocytogenes* used in combination with biosurfactants, the antiadhesive biological coating developed both reduced the total adhering flora and the viable and culturable adherent bacteria on stainless steel surfaces. More recently, another group investigated the effect of rhamnolipid and surfactin biosurfactants on the adhesion of the food pathogens *E. sakazakii*, *L. monocytogenes* and *S. enteritidis* to polypropylene and stainless steel surfaces (Nitschke et al., 2009). Preconditioning with surfactin, rather than rhamnolipid, caused a reduction in the number of adhering cells particularly of *L. monocytogenes* and to some extent *E. sakazakii* on stainless steel. Surfactin showed a significant decrease in the adhesion on polypropylene of all strains. The adsorption of surfactin on polystyrene also reduced the adhesion of S*. enteritidis*- and *L. monocytogenes*growing cells. In addition, surfactin was able to delay bacterial adhesion within short contact periods using non-growing cells or longer contact periods using growing cells.

Other antimicrobial and antiadhesive properties of a biosurfactant produced by *Lactobacillus paracasei* ssp. *paracasei* A20 isolated from a Portuguese dairy plant were also described (Gudiña et al., 2010). The biosurfactant had antimicrobial activity against a broad range of microorganisms including the pathogenic *C. albicans*, *E. coli*, *S. aureus*, *S. epidermidis* and *Streptococcus agalactiae* while exhibiting a considerable antiadhesive activity against a wide range of microorganisms.

The activity demonstrated by biosurfactants suggests that they could be considered as new tools in developing strategies to prevent or delay microbiological colonization of industrial plant surfaces used in foodstuffs preparation.
