不同分子量超高脱乙酰度壳聚度糖的制备

将甲壳素分别在含硼氢化钠的氢氧化钠-正戊醇中和氢氧化钠-水中进行脱乙酰反应,再将得到的壳聚糖用过氧化氢-水反应体系降解,制得不同分子量的超高脱乙酰度壳聚糖.在氢氧化钠-正戊醇中制备的壳聚糖分子量介于24万和35万之间,在氢氧化钠-水中制备的壳聚糖分子量介于81万和100万之间.实验结果表明:在氢氧化钠-正戊醇体系中反应5 h或在氢氧化钠-水体系中反应6 h所制备壳聚糖的脱乙酰度均达98%以上,在脱乙酰反应中,延长反应时间脱乙酰度增大;采用过氧化氢-水反应体系降解壳聚糖时,影响壳聚糖分子量的因素包括过氧化氢与壳聚糖的投料比、反应温度及反应时间,而过氧化氢与壳聚糖的投料比是主要的影响因素.改变这些影响因素,可制备出分子量介于3.2万和56万之间的壳聚糖.

Preparation of chitosan with various molecular weight and ultra-high degree of deacetylaion

In the presence of sodium borohydride,chitin was deacylated in n-pentanol/sodium hydroxide or in an aqueous solution of sodium hydroxide,followed by the degradation with an aqueous solution of hydrogen peroxide as the reaction system to obtain the chitosan with various molecular weight （M.W.）and ultra high degree ofdeacetylation （D.D.）.TheM.W.ranges from 2.4×10^5 to 3.5×10^5 when the chitosan is prepared in n pentanol/sodium hydroxide,and ranges from 8.1× 10^5 to 1.0× 10^6 when the one is prepared in an aqueous solution of sodium hydroxide.The experimental results show that the D.D.is above 98% when the chitosan is prepared by the reaction in n pentanol/sodium hydroxide for 5 hours or in an aqueous solution of sodium hydroxide for 6 hours.With respect to deacetylation reaction,the D.D.will be increased if the reaction time is prolonged.Regarding the degradation of chitosan in an aqueous solution of hydrogen peroxide,the elements influencing the M.W.of the prepared chitosan include the feed ratio of hydrogen peroxide to chitosan,reaction temperature and reaction duration.Meanwhile the feed ratio of hydrogen peroxide to chitosan is a dominant factor.By adjusting these elements,the chitosan with a M.W.ranges from 3.2×10^4 to 5.6×10^5 can be prepared.