According to our results, nisin showed a small
effect on its own at 88C, and needed to be combined
with lower pH, carvacrol, or both of them for maximum
bactericidal action. This seems to indicate that
there are changes in the membrane at 88C that
affected the target of nisin, and the other contributing
factors ŽpH and carvacrol. enabled the access to
these sites. The ordering of the lipid hydrocarbon
chains, which occurs at lower temperatures resulting
in a decrease of membrane fluidity, are probably
responsible for the reduced nisin Z efficiency observed
on L. monocytogenes ŽAbee et al., 1994..
Alterations in cytoplasmic membrane properties or
alterations in the peptidiglycan may modulate nisin
sensitivity ŽAbee, 1998.. Recently, the target site of
nisin has been shown to be the membrane-anchored
cell wall precursor Lipid II in several Gram-positive
bacteria ŽBreukink et al., 1999.. The synthesis of
Lipid II can be affected by the temperature, which
would affect the number of target sites in the membrane
and the sensitivity of bacteria to nisin.