We performed six different extraction methods that are currently used to extract sericin from B. mori and A. mylitta (Table 1). For all of the extraction procedures, the A. mylitta cocoons were cut into small pieces before the extraction and 10 g of the cocoon pieces was added to 250 ml of the extraction solutions. The heating was performed under refluxing conditions except for the hot-water
extraction. First, the conventional soap-alkaline process was used for the full extraction of sericin. The cocoon pieces were boiled without pressure in a solution containing 0.02% (w/v) of Na2CO3 and 0.03% (w/v) of Marseilles soap. A hot-water extraction was performed by boiling the cocoon pieces with distilled water at 120 ◦C for 1 h. For the urea extraction, the cocoon pieces were immersed in a 8 M urea solution and were heated at 80 ◦C for 10 min. For the urea–mercaptoethanol extraction, the same condition
as the urea extraction was adopted except the addition of 5% (v/v) 2-mercaptoethanol to the 8 M urea solution. For the NaCl extraction, the cocoon pieces were immersed in a 1% (w/v) NaCl solution and stirred at room temperature overnight. Finally, for the Na2CO3 extraction, various concentrations of the Na2CO3 solution were used.