KC sample (Gelcarin GP-911NF) was a gift from FMC Biopolymer.
This KC sample contained various metal ions and was converted
to sodium type by ion exchange using Amberlite IR-120 resin purchased
from Sigma Co., Ltd. The resin was first converted to H+ form
by washing with 1 M HCl. 1.0 wt% KC solution was prepared and was
dialyzed (Mw cutoff 8–14 kDa) against water for 24 h to remove any
free salt. The H+-form resin and the dialyzed KC were mixed at a
ratio of 1:2 and stirred for 3 h in an iced water bath to avoid acid
degradation. KC in the H+ form was separated from the resin, and
was adjusted to pH 8.0 using 1 M NaOH to obtain the sodium type
KC. The purified sample was then lyophilized on a Modulyod-230
Freeze Dryer (Thermo Electro Corporation, Germany).