電場掃流超過濾回收痲瘋樹籽蛋白質萃取液與BSA/LY混合溶液之研究

A Study on Crossflow Electro-ultrafiltration for Concentrating Jatropha Curcas Seed Protein Extract and BSA/LY protein solution

蘇宜娃(Yi-Wa Su)

指導教授 ： 莊清榮

中原大學/工學院/化學工程研究所/碩士(2014年)

https://doi.org/10.6840/cycu201400749

摘要

隨著世界經濟日益發展，全球正面臨兩大問題：全球暖化與石油危機，而藉由生質能源可達永續再生及二氧化碳零淨排放的優點，然而生質能源大多以食用農作物做為生質柴油原料，如此會有糧食競爭的問題。近年來，許多科學家發現痲瘋樹（Jatropha curcas L.）替代食用性油料做為生質柴油極具有潛力。痲瘋樹對貧濟土壤適應力強，一年生苗木即開始開花結果，可生長30~40年，種子含油量約40%，痲瘋樹籽經榨油後，廢渣中蛋白質所占比例約50 wt%，但因痲瘋樹籽具有毒性，僅可應用於材料工業中，做為乳化、發泡、黏著劑等之材料。目前回收痲瘋樹籽渣蛋白質之方法有耗能、耗時及添加化學藥劑等缺點，故如何以一種高效率、低成本的濃縮方法成為重要的議題。
薄膜過濾為單純的物理性分離，較不會破壞欲被分離物質，且已廣泛的應用於化工、食品、生化、水處理等程序中的濃縮分離。而以UF膜濃縮痲瘋樹籽蛋白質萃取液回收率可達80%以上，但膜阻塞與膜結垢為導致濾速大幅下降之主因，而形成結垢之因素眾多，包含了膜材特性及操作參數等。
本研究以MWCO為10、30及100 kDa的RC與PES膜進行痲瘋樹籽蛋白質萃取液與BSA/LY混合溶液之掃流超過濾，探討膜材孔徑、操作壓力、進料流率及外加電場對濾速與阻擋率之影響。實驗結果顯示RC膜因接觸角較小及孔隙度較大，故其濾速較PES膜高，阻擋率則較PES膜低。此外，進料流率由0.55 提高至1.5 L/min（Re = 1152.04），可減緩濃度極化現象及減少過濾阻力而使濾速有所提升；操作壓力由0.5 提高至2 bar，可提高濾速及阻擋率。
痲瘋樹籽蛋白質萃取液在無施加電場下，脫膠前處理對濾速及阻擋率不會造成明顯的影響；而在外加電場下，濾速雖有提升之現象，但磷脂卻會隨過濾的進行而逐漸附著於正電極上，使有效電場降低，然而當萃取液依序經1、0.5及0.1 μm之濾材作脫膠前處理和提高進料流率可減緩磷脂附著之現象，使濾速提高。而在本研究操作條件中，以10 kDa的RC膜在2 bar操作壓力及進料流率1.5 L/min下，阻擋率可達80%以上。
當以30及100 kDa的RC及PES膜過濾pH=7的BSA/LY混合溶液時，外加電場會使濾速降低，阻擋率則會提高。而阻擋率在0.5 bar壓力下，僅30~50%；當壓力提高至2 bar，阻擋率方能提高至80%以上。當溶液之pH=9時，濾速會隨電場強度、操作壓力及進料流率增加而有所提升，在操作壓力2 bar、進料流率1.5 L/min及電場強度2000 V/m下，濾速可達4.26 × 10-5 m3/m2/s及阻擋率92%。
濃縮痲瘋樹籽蛋白萃取液以10 kDa的RC膜在2 bar操作壓力及進料流率1.5 L/min下，可達阻擋率80以上%，而BSA/LY混合溶液以10 kDa的RC膜在pH=9、操作壓力2 bar、進料流率1.5 L/min及電場強度2000 V/m下，阻擋率可達90%以上。

關鍵字

痲瘋樹籽蛋白質 ； 超過濾 ； 電場 ； 掃流過濾

並列摘要

Global warming and energy crisis are the currently major problems of the world, and the usage of Jatropha curcas to produce biodiesel as a renewable energy source has attracted many attentions. Jatropha (Jatropha curcas L.) can grow in poor soil conditions, and its seed contains about 40% of oil. After oil extraction of crushed seed, the solid residue is rich in proteins, but it contains toxic compounds, being unsuitable for food applications. Such proteins can be used in industries for non-food applications as emulsifying, foaming, and adhesives etc.
Currently, the methods of recovering Jatropha seed protein from Jatropha waste seed cake are extracting by alkaline solvent, and then concentrating by centrifugation, isoelectric precipitation, and so on. Membrane filtration is a simple physical separation process widely used in chemical, food, biochemistry, water treatment and other procedures in the concentration and separation. With UF membrane, the recover y of Jatropha seed protein could up to 80%, but membrane fouling and blocking would lead to a significant decrease in the filtration rate. The factors in controlling the formation of fouling and blocking include membrane characteristics, operating parameters, and so on.
In this study, crossflow ultrfiltration experiments of Jatropha seed protein extract and BSA/LY protein solutions with 10, 30 and 100 kDa MWCO RC and PES membranes were carried out for investigating the effects of membrane characteristics, operating pressure, feed rate and external electric field etc.on flux and protein rejection. Experimental results with no electric field showed that the pretreatment with degumming process wouldn’t give obvious influence on filtration rate and protein retentivity. When an electric field as E=2500 V/m was imposed on, a rise in filtration rates was observed and the degummed Jatropha protein extract has a higher filtration rate than that non-gummed. Based on the experimental results from the conditions used in the study, 10 kDa RC membrane operated at 2 bar and feed flow rate at 1.5 L/min (average Re=1152) with electric field could provide a better performance in concentrating the Jatropha seed protein extract, producing a higher flux and a protein retentivity larger than 80%.
For BSA/LY protein solution, the solutions at pH=7 has a higher flux than that at pH=9 when the pressure applied is 0.5 bar. However, an opposite result in the effect of pH on filtration rate was observed if the applied pressure drop is increased to 2 bar. The retentivity of protein is higher than 90% at pH=9 by using 10 and 30 kDa PES or 10 k Da RC membranes , however, at pH=7 the retenvity of 30 kDa RC membrane at 0.5 bar is lower than 60 % and under 2 bar pressure drop 90% retentivity can be obtained. Experimental results using 30 kDa RC membranes showed that at pH=7 the filtration rate with an electric field of E=2000 V/m is lower than that with no electric field, but the former has a higher retentivity of protein.
For concentrating Jatropha seed protein extract and BSA/LY protein solution, 10 kDa RC membrane with 2 bar and 1.5 L/min could achieve higher filtration rate and recovery higher than 80%. When an electric field of 2500 V/m was imposed on filter for Jatropha seed protein extract, protein retentivity increased to about 86 %. For BSA/LY protein solution, the retentivity is up to 90% at an electric field of 2000 V/m.

並列關鍵字

crossflow filtration ； ultrafiltration ； electric field ； Jatropha curcas seed protein

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