Diluted HCl solution was used for demineralization. One hundred
grams of shrimp shell powder was immersed in 1000 ml of 7% (w/w)
HCl at room temperature (25 °C) for 24 h. After filtration with midspeed
filter paper, the residue was washed with distilled water to
neutral. Then the residue was immersed in 1000 ml of 10% (w/w)
NaOH at 60 °C for 24 h for deproteination. The proteins were removed
by filtration. Distilled water was used to wash the residue to neutral.
Then the shrimp shell residue was subjected to the above program for
two times. 250 ml of 95% and absolute ethanol were sequentially used
to remove ethanol-soluble substances from the obtained crude chitin
and to dehydrate. An air oven was taken to dry the chitin at 50 °C
overnight.