Please use this identifier to cite or link to this item:
The Study on Immobilizing Lipase on Chitosan beads of Different Degrees of Acetylation
|Authors: ||Chao-Nan Wu|
|Contributors: ||NTOU:Department of Food Science|
lipase;degrees of acetylation;immobilization;chitosan beads
|Issue Date: ||2011-06-30T07:38:27Z
|Abstract: ||幾丁質與幾丁聚醣二者皆來自天然的生物體。其具有無毒、生物可分解性及良好的生物反應性。尤其近年來食品加工及醫療檢測研究者積極從事於生物觸媒(biocatalysts)固定化之研發，以節省生產成本，提高市場競爭力。本實驗以不同乙醯化程度之幾丁聚醣珠粒依不同方法製備幾丁聚醣珠粒，進行酵素固定化，以探討不同製作珠粒的方法與不同乙醯化程度之幾丁聚醣與固定化脂肪酶活性之關係。 將N-乙醯化程度25%幾丁聚醣進行不同時間的熱鹼處理，得到不同的N-乙醯化程度約為5、10、15與20%之幾丁聚醣。利用兩種製珠粒方法(擠壓法及噴霧乾燥法)製成幾丁聚醣珠粒，並進行脂肪酶之固定化。實驗結果發現以噴霧乾燥法製備之珠粒比擠壓法製備之珠粒固定脂肪酶之活性較高；在擠壓法之中，則以凍乾之珠粒固定脂肪酶之活性>濕潤>烘乾。經凍乾之珠粒，與濕潤狀珠粒之大小相當，且表面上有形成多孔洞，使其具有較高之脂肪酶活性。 在不同N-乙醯化程度之幾丁聚醣珠粒，發現較低的N-乙醯化程度固定lipase之活性較為高，其因幾丁聚醣上的胺基(NH2)較多之關係。以三種不同固定化方法(交聯法、活化法及雙官能基固定系統)實驗，發現以雙官能基固定系統所得酵素活性較高於兩者，但其比活性並未隨之提高，此可能係因酵素固定過多而造成部分酵素失活。固定化後，脂肪酶之熱安定性與pH安定性都有顯著的提高，在數種珠粒進行批式水解p-nitrophenyl butyrate，反應第30次其酵素活性尚有90%以上。在酵素動力常數方面，固定化後脂肪酶與游離脂肪酶之Km值相近，惟固定化lipase之Vmax小於游離脂肪酶。|
Chitin and chitosan both come from natural organisms. They are nontoxic, biodegradable, and bioreactive. During the past few years, researchers in food process and medical analysis did a lot of studies on immobilization of biocatalysts to cut down the production cost in order to become more competitive for the market. Our experiment involved lipase immobilization on chitosan beads made by different methods, which possessed various degrees of N-acetylation. The effect of immobilized lipase activity on degrees of N-acetylation and preparative methods for chitosan beads were investigated. Chitosan with degrees of N-acetylation (DA) of 25% was treated with hot alkali solution for different time intervals to lower its DA to around 5, 10, 15, and 20%. Chitosan beads were then prepared by means of extrusion and spray drying. Lipase immobilized on extruded beads had lower activity than that immobilized on spray dried counterparts. Moreover, lipase on lyophilized beads had higher activity than that on wet ones. And lipase on wet beads had higher activity than that on oven dried ones. Lyophilized beads, having about the same size as wet beads and a lot of holes on the surface, possessed higher lipase activities. Lowering the DA of chitosan was also found helpful in increasing the activity of the lipase immobilized because of the more amino groups on the beads. Among the three methods employed for lipase immobilization, binary immobilization method was found to have higher activity than the other two methods. However, relative specific activities did not follow the same trend. Part of the enzyme probably denatured while too much enzyme was immobilized. Both thermal and pH stability of the enzyme were elevated after immobilization. Immobilized enzyme retained more than 90% of its original activity after 30 bath reactions. For enzyme dynamic constants, the Km value of the immobilized lipase was close to that of free lipase, while the Vmax value of the immobilized lipase was lower than that of free lipase.
|Appears in Collections:||[食品科學系] 博碩士論文|
Files in This Item:
All items in NTOUR are protected by copyright, with all rights reserved.