in the preparation of chitosan solutions, 2.5% (w/v) chitosans were dispersed in a 1.0% (v/v) acetic acid solution, whereas COS solutions were prepared by dissolving 2.5% (w/v) COS in deionized water. In both cases, the pH was adjusted to 5.8 with 10M NaOH (the pH most adequate to solubilize chitosan and without any antibacterial effect). After stirring overnight, the solutions were autoclaved at 120 oC for 15 min (thermostability under these condition had been previously checked)