| 摘要 |
PURPOSE:To obtain low-MW water-soluble chitosan useful for, e.g., drugs easily in good yields, by soaking chitosan in an aqueous solution of a nitrite, acidifying the reaction system by the addition of an acidic substance and effecting a MW reduction of the chitosan. CONSTITUTION:Chitosan is produced by, for example, a method comprising deacetylating chitin obtained by deashing and deproteinizing the shells of crabs. The obtained chitosan is soaked in an aqueous solution of a nitrile (e.g., sodium nitrite) to impregnate the porous chitosan uniformly with the nitrite. The pH of the reaction system is adjusted to 5 or below by the addition of an acidic substance (e.g., acetic acid or hydrochloric acid), and the whole system is agitated to effect a MW reduction of the chitosan. It is desirable that a nitrite is further added to the reaction system after the acidic substance has been added to it. After the reaction, the reaction mixture solution is neutralized to obtain the purpose water-soluble chitosan of a decreased MW.
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