臭氧降解法制备壳低聚糖及其结构表征

以85％脱乙酰度、相对分子质量为25×10^4的壳聚糖为原料，在20℃、pH为3、氧气流量0．7m^3／h的条件下降解6h，降解液用氨水调至pH为9，无沉淀，分别用截留相对分子质量为2k、3k、5k、10k的中空纤维膜超滤，获得所需聚合度的壳低聚糖。降解产物的结构用红外光谱、核磁共振碳谱表征，结果说明降解前后的结构基本没有变化。降解产物的聚合度用飞行时间质谱表征，其中经过2k中空纤维膜超滤后的壳低聚糖聚合度主要为4～10。

Preparation and Characterization of Chito-Oligosaccharide by Ozone Treatment

The chitosan (DD: 85.5 % ; Mw: 25×104) dissolved in acidic solution (pH=3) was treated with ozone (generated from oxygen with application flow rate of 0.7m3/h by a ozone generator) at 20°C for 6 hours. After the reaction,the degraded chitosan solution was neutralised to pH 9 by adding concentrated ammonia spirit and no precipitates was formed. The chito-oligosaccharides were separated using ultrafiltration membrane with cut-off molecular weight of 2,3,5,and 10 kDa,respectively. In addition,the chemical structure of the degraded chitosan was characterized by FT-IR,13CNMR spectra. The results indicated that there was no modification of the chemical structure of the degraded chitosan compared with the initial chitosan. The degree of polymerization of degraded chitosan was determined by MALDI-TOF mass spectrometry. The degree of polymerization of chito-oligosaccharide separated using ultrafiltration membrane with cut-off molecular weight of 2 kDa was mainly from 4 to 10.