The growing consumer demand for foods without che-mical preservatives has focused e€orts in the discovery of new natural antimicrobials [45]. In this context, the unusual antimicrobial activity of chitin, chitosan and their derivatives against di€erent groups of micro-organisms, 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 glu-cosamine 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 di€erent mechanisms have been pro-posed. Interaction between positively charged chitosan molecules and negatively charged microbial cell mem-branes 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 micro-organisms and interfering with the synthesis of mRNA and proteins [19, 49].
The growing consumer demand for foods without che-mical preservatives has focused e€orts in the discovery of new natural antimicrobials [45]. In this context, the unusual antimicrobial activity of chitin, chitosan and their derivatives against di€erent groups of micro-organisms, 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 glu-cosamine 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 di€erent mechanisms have been pro-posed. Interaction between positively charged chitosan molecules and negatively charged microbial cell mem-branes leads to the leakage of proteinaceous and otherintracellular 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 micro-organisms and interfering with the synthesis of mRNA and proteins [19, 49].
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