only contamination of the steel surfaces by viable and cultivable
adherent bacteria is discussed. The results of the bioadhesive
behavior of living cells of L. monocytogenes on bared and conditioned
stainless steel surfaces are summarized in Table 4.
Considering first the bared surfaces, differences were observed
in the amount of CFU adhering to the substratum among the
four strains studied. Therefore, the most important concentration
of viable and cultivable adhering bacteria was obtained
with the CIP103574 strain (5.0 log CFU cm−2), characterized
by averagely hydrophobic and electron-donor characters. On
the contrary, the CIP104794 strain with a strong electron-donor
character exhibited the lowest number of adhering microorganisms
(3.8 log CFU cm−2). This result could be explained by a
repulsive interaction between the bacterial cell surface and the
support, both having a strong electron-donor character.An intermediate
number of viable adhering cells (4.3 log CFU cm−2)
was obtained with the very hydrophilic strains CIP 103573 and
CIP78.39, probably due to a repulsive hydrophobic/hydrophilic
interaction between these bacterial cells and the bared stainless
steel surface. Concerning the bioadhesive behavior of the
pathogenic strains on the biologically treated surfaces (Table 1),
there were noticeable drops in the amount of adhered cells
of the four Listeria strains on steel conditioned by both biosurfactants
used in our study. The most obvious inhibitory
effect was obtained with CIP104794 and CIP103573 strains,
two hydrophilic bacteria, on Lb-conditioned supports. Indeed,
the adsorbed Lb-biosurfactant layer strongly reduced the contamination
level (in term of CFU) of the four listerial strains
by 93.62–99.77%. A same marked effect was obtained with
the surface covered by the biosurfactant produced by P. fluorescens,
except for CIP103574, a moderatly hydrophobic strain
for which the decrease of contamination was less important
only contamination of the steel surfaces by viable and cultivableadherent bacteria is discussed. The results of the bioadhesivebehavior of living cells of L. monocytogenes on bared and conditionedstainless steel surfaces are summarized in Table 4.Considering first the bared surfaces, differences were observedin the amount of CFU adhering to the substratum among thefour strains studied. Therefore, the most important concentrationof viable and cultivable adhering bacteria was obtainedwith the CIP103574 strain (5.0 log CFU cm−2), characterizedby averagely hydrophobic and electron-donor characters. Onthe contrary, the CIP104794 strain with a strong electron-donorcharacter exhibited the lowest number of adhering microorganisms(3.8 log CFU cm−2). This result could be explained by arepulsive interaction between the bacterial cell surface and thesupport, both having a strong electron-donor character.An intermediatenumber of viable adhering cells (4.3 log CFU cm−2)was obtained with the very hydrophilic strains CIP 103573 andCIP78.39, probably due to a repulsive hydrophobic/hydrophilicinteraction between these bacterial cells and the bared stainlesssteel surface. Concerning the bioadhesive behavior of thepathogenic strains on the biologically treated surfaces (Table 1),there were noticeable drops in the amount of adhered cellsof the four Listeria strains on steel conditioned by both biosurfactantsused in our study. The most obvious inhibitoryeffect was obtained with CIP104794 and CIP103573 strains,two hydrophilic bacteria, on Lb-conditioned supports. Indeed,the adsorbed Lb-biosurfactant layer strongly reduced the contaminationlevel (in term of CFU) of the four listerial strainsby 93.62–99.77%. A same marked effect was obtained withthe surface covered by the biosurfactant produced by P. fluorescens,except for CIP103574, a moderatly hydrophobic strainfor which the decrease of contamination was less important
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