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.