Poster Presenter

Improving The Antibacterial Activity Of Lysozyme By Conjugation With Polysaccharides
Aminlari M.
Iran

A widespread trend in food safety is replacing chemical additives with naturally occurring antimicrobials. Lysozyme is a well-known enzyme that has the ability to destroy bacteria by lysis of the bacterial cell wall. Lysozyme is found abundantly in nature and has antibacterial effect towards G-positive bacteria but is not effective against G-negatives due to the presence of the LPS layer in outer membrane of the latter. The purposes of this research was to glycosylate lysozyme with dextran, dextran sulfate and beta-glucan, and to study its effect on G-positive and G-negative bacteria in vitro. Lysozyme and polysaccharides were allowed to react under mild Maillard reaction conditions (60 degrees centigrade for one week), the glycosylated products were separated by ion-exchange and gel filtration chromatography and the identity of the products was confirmed by electrophoresis. The antimicrobial properties of lysozyme-polysaccharide conjugates against test microorganisms (S. aureus and E. coli) in culture media was evaluated. Under optimum conditions 3.0 moles dextran, 1.2 moles dextran sulfate and 3.6 mmoles beta-glucan were coupled to 1 mole lysozyme. Glycosylated lysozymes exhibited increased solubility at different temperatures and pH's. Evaluation of the lysozyme-polysaccharide conjugates against test microorganisms (S. aureus and E. coli) in culture media indicated an increase in antimicrobial activity in a concentration-dependent manner. The lysozyme-dextran conjugate was more effective against E. coli than unmodified lysozyme and it reduced the bacterial count by 3 log cycles. The antimicrobial action of dextran-conjugated lysozyme against S. aureus was similar to that of un-conjugated lysozyme. The effect of dextran sulfate and beta-glucan conjugated lysozyme was similar to but less significant than dextran conjugated lysozyme. These results might increase the applicability of lysozyme as a natural antimicrobial ingredient against a broader spectrum of bacteria.