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Transmission of BSA during Cross-flow Microfiltration: Influence of pH and Salt Concentration

Persson, Anna LU ; Jönsson, Ann-Sofi LU and Zacchi, Guido LU (2003) In Journal of Membrane Science 223(1-2). p.11-21
Abstract
In many downstream processes microfiltration (MF) is used as the first step to separate the micro-organisms from the product-containing broth. The transmission of proteins through these MF membranes is of great importance, especially when a protein is the desired product. Usually, the largest fraction of the proteins retained in the membrane during the separation of micro-organisms is retained in the filter cake of micro-organisms that is built up on the membrane surface. However, this is not always the case. In some cases the transmission of proteins can decrease below 100% even though there are no micro-organisms present in the broth.



In the present study the transmission of BSA through two different MF membranes (a... (More)
In many downstream processes microfiltration (MF) is used as the first step to separate the micro-organisms from the product-containing broth. The transmission of proteins through these MF membranes is of great importance, especially when a protein is the desired product. Usually, the largest fraction of the proteins retained in the membrane during the separation of micro-organisms is retained in the filter cake of micro-organisms that is built up on the membrane surface. However, this is not always the case. In some cases the transmission of proteins can decrease below 100% even though there are no micro-organisms present in the broth.



In the present study the transmission of BSA through two different MF membranes (a nylon membrane, Pall Filtron Ultipore, Nylon66, 0.2 m, and a membrane made of polyether sulphone, Pall Filtron, Omega, 0.16 m) was investigated.



The transmission of BSA was highest for the membrane that was said to be a low protein binding membrane (Omega) and it was affected by the pH in the solution. At pH 5, which is close to the IEP of the protein, the transmission was 100%, while at pH 3 and 7 the transmission was much lower (sometimes as low as 40%). However, when the ionic strength in the solution was increased the transmission of BSA through both MF membranes increased dramatically (at pH 3 and 7).



This shows that the electrostatic interactions between the protein and the filter cake (made up of protein aggregates) and between the protein and the membrane affect the transmission. The increase in transmission when the protein is close to its IEP (at pH 5), is believed to be due to the lack of electrostatic repulsion between the proteins in the solution and filter cake of protein aggregates formed on the membrane.



At high ionic strength the charged protein molecules are shielded from each other and from the membrane and the filter cake, by the ions in the solution. Due to this shielding effect the protein molecules act as if they were uncharged and the transmission of BSA is thus increased. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Membrane Science
volume
223
issue
1-2
pages
11 - 21
publisher
Elsevier
external identifiers
  • wos:000186126100002
  • scopus:0141992738
ISSN
0376-7388
DOI
language
English
LU publication?
yes
id
9441d06b-3add-446e-bf3c-10e8c4b71382 (old id 129360)
date added to LUP
2007-06-25 14:55:03
date last changed
2018-06-24 04:30:21
@article{9441d06b-3add-446e-bf3c-10e8c4b71382,
  abstract     = {In many downstream processes microfiltration (MF) is used as the first step to separate the micro-organisms from the product-containing broth. The transmission of proteins through these MF membranes is of great importance, especially when a protein is the desired product. Usually, the largest fraction of the proteins retained in the membrane during the separation of micro-organisms is retained in the filter cake of micro-organisms that is built up on the membrane surface. However, this is not always the case. In some cases the transmission of proteins can decrease below 100% even though there are no micro-organisms present in the broth.<br/><br>
<br/><br>
In the present study the transmission of BSA through two different MF membranes (a nylon membrane, Pall Filtron Ultipore, Nylon66, 0.2 m, and a membrane made of polyether sulphone, Pall Filtron, Omega, 0.16 m) was investigated.<br/><br>
<br/><br>
The transmission of BSA was highest for the membrane that was said to be a low protein binding membrane (Omega) and it was affected by the pH in the solution. At pH 5, which is close to the IEP of the protein, the transmission was 100%, while at pH 3 and 7 the transmission was much lower (sometimes as low as 40%). However, when the ionic strength in the solution was increased the transmission of BSA through both MF membranes increased dramatically (at pH 3 and 7).<br/><br>
<br/><br>
This shows that the electrostatic interactions between the protein and the filter cake (made up of protein aggregates) and between the protein and the membrane affect the transmission. The increase in transmission when the protein is close to its IEP (at pH 5), is believed to be due to the lack of electrostatic repulsion between the proteins in the solution and filter cake of protein aggregates formed on the membrane.<br/><br>
<br/><br>
At high ionic strength the charged protein molecules are shielded from each other and from the membrane and the filter cake, by the ions in the solution. Due to this shielding effect the protein molecules act as if they were uncharged and the transmission of BSA is thus increased.},
  author       = {Persson, Anna and Jönsson, Ann-Sofi and Zacchi, Guido},
  issn         = {0376-7388},
  language     = {eng},
  number       = {1-2},
  pages        = {11--21},
  publisher    = {Elsevier},
  series       = {Journal of Membrane Science},
  title        = {Transmission of BSA during Cross-flow Microfiltration: Influence of pH and Salt Concentration},
  url          = {http://dx.doi.org/},
  volume       = {223},
  year         = {2003},
}