Antibiofilm Strategies in the Food Industry - Antibiofilm Agents: From Diagnosis to Treatment and Prevention - page 361

into these materials. Price and coworkers ( 1991 ) have shown that, compared to a
control polymer, a significant decrease of attachment and viability of Klebsiella
pneumoniae , S. aureus , and P. aeruginosa was achieved on an ethylene vinyl
acetate/low-density polyethylene product containing a low-solubility commercial
quaternary amine complex. Although further studies are needed, this seems to be a
promising application to control microbial contamination on food contact surfaces.
Nevertheless, it is also important to note that not all antimicrobial coatings tested so
far have shown efficacy. For example, a polystyrene surface coated with anti-
microbial fullerene-based nanoparticles was created aiming to prevent biofilm
formation by Pseudomonas mendocina , but it actually enhanced biofilm develop-
ment (Lyon et al. 2008 ). This demonstrates that antibacterial nanomaterials can lose
their efficacy when applied as coatings.
Another possible way to avoid biofilm formation is by steric hindrance, or
blocking, of bacterial adhesion by means of a “molecular brush,” which involves
coating a surface with an inert material that physically prevents bacterial adhesion.
Namely, polyethylene glycol (PEG) is the most investigated molecular brush that
controls protein adsorption to materials (J¨nsson and Johansson 2004 ). Although
the prevention of protein adsorption by a molecular brush has generally been
established, its usefulness in preventing microbial attachment is somehow contro-
versial. In fact, Wei and coworkers ( 2003 ) have reported that stainless steel coated
with PEG inhibited the adsorption of b-lactoglobulin, but did not inhibit the
adhesion of Pseudomonas sp. and L. monocytogenes cells. A possible explanation
for these observations may be related with the particular nature of the PEG layer
used, as well as the complexity of bacterial adhesion, since protein interactions are
not the only aspect that influences it.
5.6 Natural Compounds
Recently, the emergence of antibiotic-resistant strains and the reluctance of con-
sumers toward the use of chemical products, such as biocides, have led to a search
for natural alternative products. The use of biocides as sanitizers in the food
industry has associated concerns such as biocide biodegradability, their risk to
human health, and their environmental impact (Cappitelli et al. 2006 ). The use of
substances obtained from plants is preferred since they may have been used in
traditional medicine for a long time, they are generally considered to be safe by
consumers, and are not known to cause harm to the environment (Leonard
et al. 2010 ). Essential oils (EOs) or their constituents are one of the more promising
and natural alternative antimicrobial agents. EOs are volatile, natural, complex
compounds characterized by a strong odor and are obtained from plant material
(flowers, buds, seeds, leaves, twigs, bark, herbs, wood, fruits, and roots).
Concerning their mode of action, they pass through the bacterial cell wall and
cytoplasmic membrane, disrupt the structure of the different layers of polysaccha-
rides, fatty acids, and phospholipids, and permeabilize them (Bakkali et al. 2008 ).