Chitosan is polycationic at pH < 6 and interacts readily with negatively charged substances such as proteins, anionic polysac-charides, fatty acids, bile acids and phospho lipids due to the high density of amino groups present on the polymer.Theme chanism of the antimicrobial activity of chitosan and its deriva-tives is unknown. It has been suggested that a positive charge on theNH3+group of the glucosamine monomer at pH < 6.3 allows inter-actions with negatively charged microbial cell membranes which leads to the leakage of intracellular constituents.Antimicrobial activity of chitosan is higher at low pH; this is dueto the fact that the amino groups of chitosan become ionized at pH below 6 In a study by Younes et al.it has been show nthat with reducing pH, chitosan adsorption on bacterial cells will be increased probably due to increase of chitosan positive charge.