Crab-shell chitosan was purchased from
ICN, Cleveland, and ground to a fine powder.
The chitosan solutions were prepared by
dissolving chitosan [l% or 2% (w/v)] in 0.25
N HCI. The solutions were centrifuged to
remove undissolved particles, and the pH was
adjusted to 5.6 with 1 N NaOH. At this pH,
chitosan (pKa = 6.2) is positively charged
and exhibits maximal biological activity
(Stösse1 and Leuba, 1984). Tween 80 [0.l%
(v/v)] was added to the solutions to improve
wettability.