In another study, Chen et al. [21] reported the antibacterial
eects of 69% deacetylated shrimp chitosan,
0.63% sulphonated chitosan (SC1), 13.03% sulphonated
chitosan (SC2) and sulphobenzoyl chitosan on
oyster preservation. They observed that, except in the
case of B.cereus, bacterial growth was eectively inhibited
by at least one of the above four compounds tested
at 200 ppm. Even though the sulphonation increased
the solubility of chitosan, totally dierent antibacterial
capabilities were observed for SC1 and SC2. For most
of the bacterial cultures SC1 had a very pronounced
minimal inhibitory concentration (MIC) eect even at
200 ppm level, with SC2 exhibiting no antibacterial eect
at concentrations below 2000 ppm. Chen et al. [21] suggested
that since SC2 has more sulphonyl groups, it
carries a higher negative charge than SC1, thus there
would be a greater repulsive force between negatively
charged SC2 molecules and bacterial cell walls (Table 2).