new natural antimicrobials [45]. In this context, the
unusual antimicrobial activity of chitin, chitosan and
their derivatives against dierent groups of microorganisms,
such as bacteria, yeast and fungi has
received considerable attention in recent years [46].
Because of the positive charge on the C-2 of the glucosamine
monomer at below pH 6, chitosan is more
soluble and has a better antimicrobial activity than
chitin [21]. The exact mechanism of the antimicrobial
action of chitin, chitosan and their derivatives is still
unknown, but dierent mechanisms have been proposed.
Interaction between positively charged chitosan
molecules and negatively charged microbial cell membranes
leads to the leakage of proteinaceous and other
intracellular constituents [17, 19-21, 47]. Chitosan also
acts as a chelating agent that selectively binds trace
metals and thereby inhibits the production of toxins and
microbial growth [48]. It also activates several defense
processes in the host tissue [18], acts as a water binding
agent and inhibits various enzymes [47]. Binding of
chitosan with DNA and inhibition of mRNA synthesis
occurs via chitosan penetrating the nuclei of the microorganisms
and interfering with the synthesis of mRNA
and proteins [19, 49].