Biomedical Engineering Reference
In-Depth Information
ester bonds of polysaccharides, which are the main constituents of microbial
adhesives (Moss
2006
). van Speybroeck et al. (
1996
) reported the use of an
enzymatic preparation comprised of exopolysaccharide-degrading enzymes, par-
ticularly the colanic acid-degrading enzymes, derived from a strain of
Streptomyces
for the removal and/or prevention of biofilm formation on surfaces.
Molobela et al. (
2010
) tested proteases (savinase, everlase, and polarzyme) and
amylase (amyloglucosidase and bacterial amylase novo) activity on biofilms
formed by
P. fluorescens
and on extracted EPS. They observed that everlase and
savinase were the most effective enzymatic treatments for removing biofilms and
degrading the EPS.
Enzymes have also been used as antibiofilm coatings. In this case, they can be
either covalently grafted onto solid substrates or incorporated into polymer matrices
to produce antibacterial coatings and it is thought that enzymes impair one or
several “bricks” of the biofilm construction (Glinel et al.
2012
). Yuan and
coworkers (
2011
) tested a coating composed by coupling lysozyme on a PEG
layer against two different bacterial species, Gram-negative
E. coli
and Gram-
positive
S. aureus
. These authors observed that more than 90 % of
S. aureus
and
~80 % of
E. coli
that adhered to lysozyme-functionalized surfaces were damaged
within 4 h. In addition, these coatings showed long-term activity since the
antibacterial effect against
S. aureus
was retained after a contact time of ~36 h.
However the effect faded over time for
E. coli
. This result was probably due to the
fact that lysozyme is more active toward peptidoglycans present in the Gram-
positive bacterial wall than toward the double membrane of the Gram-negative
cell wall. It can be concluded that, as the structural composition of EPS varies even
among bacteria of the same species, the mode of action and the consequent
efficiency of enzymes will also be variable.
Therefore, enzymes constitute an important alternative for biofilm removal in
the food industry. Though, it must be noted that enzymes, as coatings, may
contribute to the unwanted degradation of substances surrounding the surface
coating. In addition, enzymes that produce biocidal substances have to be approved
by the appropriate legislative body before being implemented.
5.8 Quorum-Sensing Interfering Molecules
Quorum sensing (QS) or cell-to-cell communication is employed by a diverse group
of bacteria, including those commonly associated with food. Through the mecha-
nisms of QS, bacteria communicate with each other by producing the signaling
molecules known as autoinducers and are consequentially able to express specific
genes in response to population density. Since several types of signaling molecules
have been detected in different spoiled food products, disrupting the QS circuit can
potentially play a major role in controlling microbial gene expression related to
human infection and food spoilage (Bai and Rai
2011
). QS inhibitors can be
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