影響幾丁聚醣應用範圍的重要參數分別為分子量和去乙醯度。
　　本研究以幾丁聚醣為基材，採用酵素降解方式，觀察經溶菌酶溶液降解幾丁聚醣膜和幾丁質膜重量變化，以及將降解效率更高的纖維酵素溶液加入幾丁聚醣溶液中，分別用黏度計、凝膠滲透層析儀、X射線繞射儀、核磁共振光譜和擴散排序光譜，得到分子量和分子量分佈、結晶度、去乙醯度和擴散係數。觀察酵素降解對幾丁聚醣的分子量和去乙醯度變化其中的依存關係，期以在溫和條件下，製備出適於改質的幾丁聚醣。纖維酵素濃度1000 µg/mL，降解反應十二小時，可使幾丁聚醣分子量從500 kDa降至50kDa，而分子量分佈由7.02減到2.53。同時顯示隨分子量降低，結晶度增加，去乙醯度不受影響。證明對500 kDa，去乙醯度85%的幾丁聚醣，經纖維酵素降解反應，對產物具有較高選擇性，分子量分佈變窄，較易調控高分子物化性質，而維持原有高去乙醯度 (85%)也確保其生物醫學材料等領域的應用。

　　In order to select an ideal chitosan species as a material for further chemical modification, the relationship between molecular weight and degree of deacetylation was investigated for chitosan through enzymatic degradation.
　　Through this study we use viscometry, GPC and DOSY for analyzing molecular weights and diffusion coefficients; XRD and 1H NMR to determine the crystalline index and degree of deacetylation, respectively. The results showed that the cellulase degradation was by endo-action, and degree of deacetylation did not change after degradation. The decrease of molecular weight led to transformation of crystal structure, but the chemical structures of residues were not modified. Within 12 hours, molecular weight of chitosan was decreased from 500 kDa to 50 kDa and PDI from 7.02 till 2.53, under 1000 µg/mL cellulase. Enzymatic degradation is a mild and specific method to get chitosan for more investigations and applications.

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