But at higher pH (>6), chitosan tends to lose its charge and mayprecipitate from solution due to deprotonation of the amino groups.reported that antibacterial activ-ity of chitosan against Klebsiella pneumoniae was closely associated with its polycationic nature, and depended on the degree of proto-nation of the chitosan amino groups, which, in turn was the function of the degree of polymerization and the pH values of the medium. showed that native chitosan was significantlymore active against Candida lambica at pH 4.0 than at pH 6.0. Also,it was demonstrated by Roller and Covillthat inhibitory prop-erties of chitosan against Mucor racemosus were greater at lower pH. In another study, antimicrobial capacity of chitosonium acetatefilms against the growth of Staphylococcus aureus in pH 6.2 and pH7.4 was investigated by .heir tests carriedout at a lower pH, i.e. 6.2, showed less bacterial counts indicating astronger biocidic effect; this finding is related to the particular pKa of this biopolymer,which is near the pH 6.2 value. At this pH, the amount of positively charged amino groups (active groups)is close to 75% in chitosan while at pH of 7.4, this quantity dropsuntil approximately 10%.