| abstract |
PURPOSE:To obtain a peptide having excellent hygroscopicity, moisture retentivity, long-term storage stability, etc., by dissolving silk fibroin or collagen in an aqueous medium to give an aqueous solution of protein, adding a chelating agent to this solution, and finely filtering this mixture after adjusting the pH. CONSTITUTION:An aqueous solution of protein is prepared by either of the following processes: (i) silk fibroin, obtained from, e.g., raw silk or a cocoon by drying after removing sericin therefrom in warm water in the presence of an enzyme, is added to a 10-80wt% solution of the chloride or nitrate of Ca or Mg in water and dissolved therein by heating to 60-95 deg.C; and (ii) natural collagen is dispersed in water, the pH of the dispersion is adjusted to 1.5-4.0, an acid-resistant protease (e.g., pepsin) is added thereto, and the mixture is stirred for 2-3 days to dissolve the collagen. This aqueous solution of protein is mixed with 0.01-10.0wt% hydrolytic enzyme (e.g., pronase) and hydrolyzed at pH5-9 and 20-70 deg.C for 0.1-72hr, to which 0.10-10wt%, based on the peptide, chelating agent is added. This mixture is adjusted to pH4.5-7.5, finely filtered through holes of 1mu or less in diameter, and dried to give a peptide having an average degree of polymerization of 2-600. |