以電場掃流微過濾分離酵母菌/牛血清蛋白混合懸浮液

Crossflow Electro-Microfiltration of Yeast/BSA Mixture

吳振溢(Chen-Yi Wu)

指導教授 ： 莊清榮

中原大學/工學院/化學工程研究所/碩士(2004年)

https://doi.org/10.6840/cycu200400506

摘要

摘要

在生化程序中，常須將發酵槽內之菌體粒子/蛋白質混合懸浮液進行固液分離，以利於下一階段之純化操作，傳統的分離方式為離心，但其缺點為無法連續式大量操作，雖然掃流過濾可改善此缺點，但過濾過程中，膜結垢及如何維持高的蛋白質穿透率則是另一個在工程應用上必須克服的問題。利用外加電場輔助掃流過濾已有廣泛探討，但對此類混合懸浮液之研究與應用則甚少觸及，本研究以酵母菌/BSA混合懸浮液為對象，探討電場強度及其它操作條件對其分離效能的影響。
除菌體粒子與蛋白質分子之帶電性受pH值影響外，膜材的電性亦深受影響，故粒子及蛋白質之電泳與膜材之電滲透等作用，其程度必隨pH 值及施加電場強度而變化。在pH=4~7之實驗範圍內，酵母菌(1000 ppm)/BSA(1000 ppm)之濾速皆約隨電場強度提高而呈線性增加，經由與穩定濾速理論模式及濾餅量之量測結果相比較，可判定該混合懸浮液中，菌體粒子之電動行為可以單成分之酵母菌特性描述之。由於濾餅層具有攔阻蛋白質團的功能，故該混合懸浮液過濾後，膜面被BSA阻塞的程度明顯低於BSA溶液過濾者。蛋白質穿透率受電場強度及pH值的影響相當大，若 BSA帶負電，其電泳作用為遠離膜面，穿透率會有明顯下降；若BSA帶正電，則其朝向膜面之電泳作用結果，穿透率會大幅增加，最高可達120％。
在BSA濃度固定1000 ppm而酵母菌濃度500~1500 ppm且未施加電場時，濾速隨菌體濃度提高而遞減，但穿透率則相反，整體蛋白質回收量以酵母菌(500 ppm)者最高，在電場作用下，酵母菌(500 ppm)/BSA(1000 ppm)之濾液量較酵母菌(1000 ppm)/BSA(1000 ppm)者多，但隨著電場強度提高此增加量會遞減，蛋白質穿透率皆稍低於酵母菌(1000 ppm)者。使用孔徑0.2及0.45 μm兩種膜材之結果，兩者之穩定濾速相似，而使用0.45 μm膜材之BSA穿透率在電場操作範圍下皆可達100％以上，最高可達123％。
脈衝式電場操作之濾速介於未施加電場與固定式電場兩者之間，而其BSA穿透率則與固定式電場者相近，但於高電場強度時，脈衝式電場操作甚至具有較高之穿透率。於電場強度2000及3000 V/m時，脈衝式電場之電能消耗率較固定式電場者低14及23％，在實驗室小規模裝置中，電場過濾之電能消耗率高於未施加電場者，若將規模放大至工業級應用的話，預期應可大幅減少電場過濾之電能消耗率。

關鍵字

牛血清蛋白 ； 酵母菌 ； 掃流微過濾 ； 電場 ； 蛋白質

並列摘要

ABSTRACT

The separation of proteins from microbial cell suspension is generally an essential operation in the bio-product processes. Centrifugal sedimentation has been widely used for the separation, however, the difficulty in scale-up for its continuous operation is not yet overcomed. Although the crossflow filtration can improve the drawback and has fairly extensive application, but in the membrane filtration process there are some disadvantages like the occurrence of membrane fouling and the difficulty in maintaining high recovery of protein. A combination of crossflow shearing action and electric field has been developed and recognized as an effective means for reducing both concentration polarization and membrane deposition in crossflow filtration. But so far, the understanding of the principles of such process is still very limited, especially for the application in the biomaterial suspension separations. The objective of this study is to investigate the effects of electric field strength, electric field mode and other operation parameters such as pH and membrane pore size etc. on the filtration performance of BSA/yeast suspensions.
Experimental results from yeast (1000ppm)/BSA(1000ppm) suspensions in the pH range from 4 to 7 showed that its filtration rate increased almost linearly with the electric field strength. Based on the comparison of the measured steady-state filtration rates with that predicted from theoretical model, it was indicated that the electrophoretic mobility of yeast in pure yeast suspensions can be used in the prediction for the mixture.
Since the charge polarity and zeta potential of BSA will be varied with the pH, therefore both the electric field strength and the pH will give significant influences on its transmission. At pH=4 its electrophoretic mobility is directed toward to the septum and a 120% high transmission was obtained under the electric field strength of 2000V/m.
Filtration performance from two different pore size membranes, 0.2 and 0.45 μm, were also compared. Both gave similar results in steady-state filtration rate, but the larger pore membrane can maintain a BSA transmission over 100% , even to 123%, under the addition of electric field.
The average filtration rate of pulsed electric field mode with on(30)/off(30) is nearly the mean value between that of constant electric field and that without electric field. Both constant and pulsed electric field modes have similar BSA transmission under low electric field strengths, however the later will give higher transmission as higher electric field is applied. Although the energy consumption per unit mass of protein recoveried from the lab-scale electrofiltration is much larger than that from conventional crossflow filtration, but it can be expected that the energy consumption will be reduced significantly for the operation in a large scale process.

並列關鍵字

BSA ； protein ； yeast ； crossflow-microfiltration ； electro

參考文獻

陳信宇，“以脈衝式電場掃流超過濾分離牛血清蛋白溶液”，碩士學位論文，中原大學化工所 (2002)

A. Claudia Sousa, Joaquim M.S. Cabral and Marilia Mateus, “Microfiltration of cutinase and Escherichia Coli cell fragment suspensions The role of the electrolyte environment on the development of dynamic cake layers ”, J. Membrane Sci., 207, p171~187, (2002)

Akay G., B. Keskinler, Y.K. Bayhan and E. Erhan, “Effect of ionic environment on the crossflow microfiltration behaviour of yeast suspensions”, J. Membrane Sci., 206, p351~360, (2002)

Anna Persson, Ann-Sofi Jonsson and Guido Zacchi, “Transmission of BSA during cross-flow microfiltration: influence of pH and salt concentration”, J. Membrane Sci., 223, p11~21, (2003)

Arora N. and R. H. Davis, “Yeast Cake as Secondary Membrane in Dead-end Microfiltration of Bovine Serum Albumin”, J. Membrane Sci., 92, p247~256, (1994)