**2. Adhesion and microbial biofilms**

The interest of biosurfactants as alternative medicines and antimicrobial agents increased considering the safe use as effective therapeutic agent on human and animal cells [12]. In consequence, the microbial adhesion is mediated by specific interactions between cells surface structures and molecular mass on the substratum surface, or by non-specific interaction forces, including electrostatic forces, acid-base interactions and Vander Waals forces [13].

during exponential growth, presumably as a result of increased cell wall hydrophobicity during this growth phase

246 Practical Applications in Biomedical Engineering

been widely studied [11].

of their low toxicity and biodegradability [7,12].

**2. Adhesion and microbial biofilms** 

may be used as safe and effective therapeutic agents [6].

economically; however, much effort in process optimization and at the engineering and biological levels have been carried out [5]. Despite their potential and biological origin only a few studies have been carried out on applications related to the biomedical field [6]. Some biosurfactants are suitable alternatives to synthetic medicines and antimicrobial agents and

Furthermore, biosurfactants have been found to inhibit the adhesion of pathogenic organisms to solid surfaces or to infection sites hampering biofilm formation that is the cause of many diseases, as for example cystic fibrosis [7]. Therefore, prior adhesion of biosurfactants to solid surfaces might constitute a new and effective means of combating

Pre-coating vinyl urethral catheters by running a surfactin solution through them before inoculation with media resulted in a decrease in the amount of biofilm formed by *Salmonella typhimurium*, *S. enterica*, *Escherichia coli* and *Proteus mirabilis* [10]. Given the importance of opportunistic infections with *Salmonella* species, including urinary tract infections of AIDS patients, these results have great potential for practical applications. In addition, the use of lactobacilli as a probiotic for the prevention of urogenital infections has

Microbial surfactants are not yet competitive with those produced by the chemical industry, but efforts should be made on the different production aspects to find suitable and economic substrates and to develop new strategies to increase the volumetric productivity. We have shown that the co-utilization of ground-nut oil refinery residue and corn steep liquor is an attractive choice for biosurfactant production. The biosurfactant adhesive mechanism is based in the inhibition of microorganisms to different surfaces can interact with interfaces of the molecule. In this sense, they are an alternative to synthetic surface-active agents because

Considering the lack of studies with yeasts biosurfactants for medical purposes, and is an attractive characteristics showed by produced by the *Candida lipolytica* (Rufisan) and *Candida sphaerica* (Lunasan). In this sense the revision shown the role and applications of rufisan and lunasan biosurfactant as a antimicrobial and antiadhesive activities were investigated against pathogenic and nonpathogenic microorganisms, and indicated the therapeutic perspectives.. Results gathered in the current work showed the potential of those molecules in this field of application; however, its use still remains limited, possibly as due to high

The interest of biosurfactants as alternative medicines and antimicrobial agents increased considering the safe use as effective therapeutic agent on human and animal cells [12]. In consequence, the microbial adhesion is mediated by specific interactions between cells surface structures and molecular mass on the substratum surface, or by non-specific interaction forces,

including electrostatic forces, acid-base interactions and Vander Waals forces [13].

production costs, as well as on their toxicity towards human systems.

colonization by pathogenic microorganisms and subsequent biofilm formation [8,9].

The conditioning film on the biomaterial surface (and on the bacterial cell surface) plays an important role, as it changes the physicochemical properties of the interacting surfaces. Albumin is a strong adhesion inhibitor, for unknown reasons, although changes in hydrophobiciy and sterical hindrance are proposed as mechanisms [14].

The adhesion of microorganisms to a surface is one of the first stages in the development of a biofilm and is believed to be influenced by a number of factors. As the substrate is essential in the development of a biofilm, an understanding of how substrate properties affected the adherence of bacterial cells my assist in designing or modifying substrates inhibitory to bacterial adhesion. Many of these molecules are proteinaceous constitution, such as serum albumin, fibrogen and collagen, and some have been shown to affect subsequent bacterial adhesion [13].

The formation of infectious biofilm on biomaterial appeared to involve several sequential steps. Immediately after exposure of a device to body fluids, such as blood, saliva, or urine, macromolecular components adsorb to form a conditioning film [15]. The most microbial surfactants are complex molecules, comprising different structures that include peptides, glycolipids, glycopeptides, fatty acids and phospolipids, as reviewed recently. Among the many classes of biosurfactants, lipopeptides are particularly interesting because their high surface activities and antibiotic potential. Lipopeptides are molecules act as antibiotics, antiviral and antitumoral agents, and enzyme inhibitors. Those molecules enhance or decrease the bacterial surface hydrophobicity following that the surface is less or more hydrophobic[16]. Morikawa et al. [17] identified and characterized a biosurfactant, arthrofactin, produced by *Arthrobacter.*

Glycolipids are the most common class of biosurfactans of which the most effective from the point of view of surface active properties arethe trehalose lipids of *Mycobacterium* and related bacteria, the rhamnolipids of *Pseudomonas* sp and the sophorolipids of yeasts [18]. Otto et al. [19] described the production of sophorose lipids from deproteinized whey concentrate by a two-stage process. Several antimicrobial, immunological and neurological properties have been attributed to mannosylerythritol lipid (MEL), a yeast glycolipid biosurfactant, produced from vegetable oils by *Candida* strains.
