蛋白質與薄膜間之界面現象對其過濾行為影響之研究

A Study on the Effect of the Interfacial Phenomena between Protein and Membrane on the Ultrafiltration Behavior

方怡蘋(Yi-Ping Fang)

指導教授 ： 莊清榮

中原大學/工學院/化學工程學系/碩士(2008年)

https://doi.org/10.6840/cycu200900220

摘要

膜過濾已廣泛應用於生物懸浮液之固液分離操作，但膜結垢會造成濾速嚴重衰減及影響薄膜之分離效能，本研究係以BSA及LY等蛋白質溶液進行吸附及掃流過濾實驗，討論不同操作條件對其分離效能之影響，並配合XDLVO理論估算蛋白質與薄膜及蛋白質與蛋白質間之作用能量，探討其交互作用能量與其過濾行為之關聯，並與傳統DLVO理論比較，分析親疏水作用能量對過濾行為之重要性。
將表面附著層蛋白質之薄膜，分別以純水及二碘甲烷進行接觸角量測，BSA與LY之對水接觸角分別為63.74o及79.08o，顯示LY較BSA疏水。分別將薄膜與蛋白質所量測之接觸角數據結合Young’s equation，即可求得膜材與蛋白質之表面張力參數，並用以估算蛋白質與膜面及蛋白質相互間之作用能量。
於蛋白質吸附實驗結果顯示，由於PTFE膜表面較疏水且其與蛋白質間之靜電吸引力較大，因此其蛋白質吸附量高於PC膜，且實驗結果與以XDLVO理論所預估之結果定性相符。
而掃流超過濾結果顯示，大孔洞之薄膜其濾速較高，但BSA易滲入膜孔，於孔壁形成結垢，造成膜孔阻塞，故濾速衰減較快，反之，當膜孔較小時，於過濾後期濾速較為穩定。比較PES膜及RC膜進行牛血清蛋白溶液掃流過濾之結果，於蛋白質等電點時，RC膜過濾之濾速衰減程度低於PES膜，此因RC膜之表面較親水，蛋白質不易附著於其上，過濾阻力變化較小。
以XDLVO理論計算不同pH值下之牛血清蛋白分別與PES膜間之作用能量，預估過濾初期於pH = 7.0時濾速最大，其次為 pH = 3.0，pH = 4.7時濾速最小，但以DLVO理論所預估之濾速大小則依序為pH = 3.0、7.0及4.7，對照實驗結果，以XDLVO理論所預估之結果較為準確。而估算蛋白質與RC間之作用能量，其以XDLVO理論所預估結果亦與實驗結果趨勢相似。當親疏水作用能量於作用總能量中所佔比例較大時，以傳統DLVO理論所計算之作用能量趨勢，無法完全預估實驗結果，而以XDLVO理論較能完整描述薄膜與蛋白質間之作用能量。
於電場過濾中，以MWCO為100 kDa之PES膜過濾BSA溶液，並對系統施加5000V/m之電場，其濾速較未施加電場時提升約1.5倍，蛋白質之穿透率下降約3倍，顯示施加電場可使濾速增加，並提高薄膜之分離效能。

關鍵字

超過濾 ； extend-DLVO理論 ； DLVO理論 ； 蛋白質溶液

並列摘要

Membrane filtration has been widely used in the separation of bio-suspensions, however, membrane fouling is still a troublesome problem in the application of membrane filtration. The fouling results from a combination of the hydrodynamics on the particles and chemical interactions between the particle and membrane. The objective of this study was to investigate the effect of chemical interactions between protein and membrane and that between protein each other on the ultrafiltration performances. Experiments of adsorption and crossflow ultrafiltration were carried out with BSA and Lysozyme solutions. In order to analyze the effect of additional interaction induced by the polarity of the solvent (acid-base interactions) on the filtration performance, an extended DLVO(XDLVO) model was used in the study to account for the total interactions and also compared to the interactions evaluated by the classical DLVO theory.
The hydrophobicity of the proteins were determined by measuring the contact angle of protein layers preformed by dead-end filtration. It was observed that BSA and LY have contact angles as 63.74o and 79.08o, respectively. Based on the contact angles data of the membrane and proteins, the surface energy parameters of membrane and proteins were calculated by Young’s equation and then were applied to determine the interaction energy between the protein and membrane and between protein particles.
Experiment results of protein adsorption showed that adsorbability of protein with PTFE membrane was much higher than that with PC membrane due to the farmer membrane is more hydrophobic nature and also has a higher electrostatic interaction force with the protein.
Experimental results of cross-flow ultrafiltration at the isoelectric point of proteins showed that the decline of normalized flux using RC membrane is lower than that with PES membrane, due to the more hydrophilic nature of RC membrane will lower the protein adsorption on membrane surface.
The interaction energy between protein and membrane was estimated by XDLVO and DLVO approach. Based on the interaction energy between BSA and PES membrane evaluated by XDLVO at pH=3~7, it was expected that at the initial stage of filtration the highest filtration flux is at pH = 7.0 and the lowest flux at pH = 4.7. However, the results from classical DLVO theory indicated that the highest flux may occur at pH = 3.0. As compare the predicted tendency in flux decline with the experimental results, it appeared that the prediction based on the XDLVO theory is more agree with the filtration flux behavior.
In addition, the application of electric field to enhance ultrafiltration of protein solution was also analyzed in the study. Experimental results of filtering BSA with 100 kDa PES membrane indicated that the applying electric field at E=5000 V/m will lead to 1.5 times increase in flux and 3 times decrease in transmission of protein. It means that cross-flow electrofiltration used a combination of shearing action and electric field can apply to increase filtration rate and separation performances.

並列關鍵字

Ultrafiltration ； extend-DLVO ； DLVO ； protein solution

參考文獻

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