Decolorization of Chitin from Silkworm Chrysalis

The colored chitin has been isolated from silkworm chrysalis with protein being extracted off with NaOH solution. The decolorization of the colored silkworm chrysalis chitin was performed by aq. H 2O 2 solution treatment. The conditions for taking off protein are as follows:m(5%NaOH)∶m(silkworm chrysalis residue)=80∶30, 70 ℃ and 2 h. The calcium containg salts can be taken off completely with 3%HCl in conditions of 2 h, 25 ℃ and m(3%HCl)∶m(silkworm chrysalis residue)=8∶3. The colored crude chitin without protein and salts can be decolored by H 2O 2 treatment in conditions of 65～70 ℃, pH 8.5±0.5, 5 h and m(30%H 2O 2)∶m(silkworm chrysalis residue)=130∶50. The yield of white chitin is 25% with whiteness above 30%. It suggested that H 2O 2 oxidizes the sulfur of cysteine present in the system of iron-sulfur center and and the cytochromes and changes it into sulfoxides, causing the chemical bond between the chromoprotein and the chitin to be broken and chromoprotein to be separated.