Interfacial Phenomena Analysis on Crossflow Ultrafiltration for Protein Mixtures

• Main Authors: Chia-Ling Li, 李佳玲
• Other Authors: Kuo-Lun Tung
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/m6fw3b

碩士 === 中原大學 === 化學工程研究所 === 92 === Purification of the desired protein from the isolated protein mixture plays a vital role in the downstream processing of biotechnology industry. However, among the bioseparation steps, purification is aimed at highly selective for the product and removes impurities of similar physical properties and chemical functionality. How to purify desired protein from isolated mixture containing tremendous diversity of proteins effectively and continuously is an anathema for many engineers. In the past decade, membrane filtration is reported to be an essential mode of filtration for recovering valuable biological materials from manufacturing processes. Although ultrafiltration is frequently regarded to be effective for protein purification, the concentration polarization and membrane fouling remain the main obstacles to the application of UF for protein purification. Purpose of this study is to reveal the membrane fouling mechanism by interfacial analyses. These include the role of protein-protein and protein-membrane interactions, the effects of operating conditions and the membrane surface hydrophobicility. Firstly, UF of <a href="http://www.ntsearch.com/search.php?q=single&v=56">single</a> protein of bovine serum albumin (BSA), ovalbumin (OV) and lysozyme (LY), respectively, under various operating conditions of pH, ionic concentration and polyethersulfone (PES) membrane surface hydrophobicility were investigated to analyze the protein-membrane interfacial phenomena. Then, binary protein mixtures of BSA/LY and BSA/OV were conducted by changing the pH, ionic concentration, crossflow velocity, transmembrane pressure, solute composition and the PES membrane surface hydrophobicility were depicted to obtain the optimum operating conditions for the purpose of high flux and selectivity. Finally, the obtained criteria were applied to multiple protein mixtures of BSA+OV+LY and CON+OV+LY in order to examine the validity of the optimum operating criteria for protein UF. The preliminary results indicate that the electrostatic strength plays a vital role in the deposition and transmission of protein, while the steady state flux, protein adsorption and interaction among proteins depend mainly on the net charge of protein. For binary protein mixture with opposite electric charge of BSA+LY, there is a highest transmission for LY under the circumstance of strongest attraction between BSA and LY. The transmission of LY as well as steady-state flux is also increase as the increase of ionic concentration. Experimental analysis on the effect of operation conditions on the protein UF indicate that increase of transmembrane pressure will reduce the concentration polarization problem and result in a higher steady-state flux. Adequate control of crossflow velocity can also effectively reduce membrane fouling and improve the concentration polarization problem due to the change of protein composition in the of cake layer and regulating the electrostatic <a href="http://www.ntsearch.com/search.php?q=distribution&v=56">distribution</a> on the cake surface. On the effect of hydrophibility of membrane on the performance of protein UF, the hydrophobic membrane would cause serious protein adsorption on the membrane and result in a lowest amount of transmission of protein at its isoelectric pH value. For binary protein mixture with similar molecular weight in size, say BSA+OV, the hydrophilic treated PES membrane facilitated the transmission of hydrophobic protein OV through the membrane and thus improves the selectivity of membrane separation. However, experimental results show that the electrostatic interaction plays a more important role than hydrophobic interaction on the performance of protein UF. Finally, an optimal operating criterion has been proposed and validated by UF of multiple protein mixtures of BSA+OV+LY and chicken egg white of CON+OV+LY. The proposed criteria would be helpful for <a href="http://www.ntsearch.com/search.php?q=engineering&v=56">engineering</a> <a href="http://www.ntsearch.com/search.php?q=design&v=56">design</a> of continuously operating equipment for protein purification by UF.