Sudharshan et al. [19] studied the antimicrobial efect of water-soluble chitosans such as chitosan lactate, chitosan hydroglutamate and chitosan derived from Absidia coerulea fungi, on di€erent bacterial cultures. They observed that chitosan glutamate and chitosan lactate were also bactericidal against both gram-positive and gram-negative bacteria in the range of one to Rve log cycle reduction within one hour. In that same study these authors reported that chitosan was no longer bactericidal at pH 7 due to two major reasons, namely presence of a signiRcant proportion of uncharged amino groups and poor solubility of chitosan. These results are
in agreement with Rndings of Papineau et al. [17] in a similar study where a concentration of 0.2 mg/mL chitosan lactate appeared most efective against E.coli with a corresponding population drop of 2 and 4 log cycles with in 2 min and 1 h exposure, respectively. These authors observed that chitosan glutamate was also efective against yeast cultures such as Saccharomyces cerevisiae and Rhodotorula glutensis and inactivation was rapid and complete within 17 min when exposed to 1 mg/mL chitosan lactate. However, in contrast to the Rndings of Sudharshan et al.[19], Papineau et al. [17] observed that chitosan hydroglutamate was a more efective antagonist than chitosan lactate. Results further suggested that chitosan acted mainly on the outer surface of the bacteria. At a lower concentration, the polycationic chitosan did probably bind to the negatively charged bacterial surface to cause agglutination, while at higher concentrations the larger number of positive charges may have imparted a net positive charge to the bacterial surfaces to keep them in suspension.