protein transport and fouling behavior of zwitteronic ultrafiltration membranes
Open Access
- Author:
- Hadidi, Mahsa
- Graduate Program:
- Chemical Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 27, 2013
- Committee Members:
- Andrew Zydney, Thesis Advisor/Co-Advisor
- Keywords:
- Zwitterion
Ultrafiltration
Fouling
Protein
Surface modification
Charge ladder - Abstract:
- The need for robust, cost-effective, and high-resolution methods for the purification of recombinant proteins has created a need for ultrafiltration membranes with lower fouling behavior and high selectivity. Several recent studies have shown that zwitterionic membranes can be low fouling while retaining some of the benefits of electrically-charged membranes in terms of their high permeability and selectivity. The overall objective of this thesis was to develop a more fundamental understanding of the performance characteristics of zwitterionic membranes by comparing the properties of a series of charged, neutral, and zwitterionic membranes with similar pore size / permeability. The surface-modified membranes were generated by covalent attachment of small ligands to a base cellulose membrane. The membranes were characterized using streaming potential measurements, XPS, protein fouling, and protein transmission. The latter was examined using lysozyme and α-lactalbumin charge ladders, which consist of a series of chemical derivatives of the base protein differing by single charge groups that can be analyzed by capillary electrophoresis. The sieving coefficients were analyzed using available hydrodynamic models based on the partitioning of a charged sphere in a charged cylindrical pore. The zwitterionic membranes showed minimal protein adsorption and a very low degree of protein fouling over a wide range of conditions. The fouling behavior of the charged membranes was strongly influenced by electrostatic interactions, although the zwitterionic membrane had a lower degree of fouling than the charged membranes even when the protein and membrane had like polarity. The low protein fouling characteristics, coupled with their high selectivity, makes these zwitterionic membranes promising candidates for high performance ultrafiltration processes.