Cost-effective large-scale protein bioseparation will be the key issue for the biopharmaceutical industry in the coming years. Conventional protein purification techniques are severely limited in the sense that they give either good selectivity of separation at the cost of throughput or vice versa. Synthetic membrane based bioseparation techniques such as high-resolution ultrafiltration and membrane chromatography have the potential to combine high-throughput with high selectivity. This thesis focuses on approaches for obtaining both selectivity and throughput in membrane based protein bioseparation processes.
Obtaining high selectivity is one of the main objectives in high-resolution ultrafiltration. This thesis reports a novel approach for flexibly manipulating the selectivity of protein separation using a dual-facilitating agent. In this study it has been shown for the first time that the selectivity of separation can be altered as desired, i.e. if required, the selectivity can be reversed and thereby smaller proteins can be retained and larger proteins can be made to permeate by using a dual-facilitating agent. The results are explained in terms of protein-protein electrostatic interactions and Donnan effect. This novel approach is expected to significantly increase the flexibility of carrying out high-resolution ultrafiltration.
Membrane chromatography is based on the use of stacks of microporous synthetic membranes as chromatographic media. Due to lower binding capacities of commercial membranes in comparison to conventional beads for packed bed chromatography, the
commercial success of membrane chromatography is largely limited to the flow-through applications. The study on membrane chromatography addresses the performances of new types of high-capacity macroporous gel-filled membranes for ion-exchange chromatography of proteins. This work demonstrates the suitability of using one of these novel membranes for fractionation of plasma proteins.
Membrane fouling reduces product throughput and is considered a major problem in pressure driven membrane processes such as microfiltration and ultrafiltration. This thesis reports some significant contributions in the area of membrane fouling. A novel yet conceptually simple approach for modeling flux decline in constant pressure ultrafiltration, which takes into account the interplay between flux, concentration polarization and membrane fouling is discussed. Conventional fouling models account for the effects of concentration polarization and membrane fouling in a simple additive way. The basic hypothesis in the model discussed here is that flux decline in constant pressure ultrafiltration is self-attenuating in nature. This new approach is expected to be very useful in deciding the start-up conditions in membrane processes. Despite widespread use of in-line microfiltration for sterilization of therapeutic proteins prior to formulation, there has been no systematic study on fouling in such processes. Part of the fouling work in this thesis examines how resistance to filtration increases during in-line microfiltration of concentrated protein solution and the mechanism of protein fouling. It assesses the severity of fouling in terms of apparent reversible fouling and irreversible fouling. Traditional methods to measure the protein fouling resistances of membranes are time consuming and expensive. This thesis reports three protocols to compare the performance of microfiltration membranes for protein filtration. The first protocol, which is based on accelerated fouling in the dead end mode using pulsed injection technique is rapid, simple, and cost effective and gives valuable information about membrane performance. The remaining two protocols are based on the critical flux concept. / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/29703 |
| Date | January 2007 |
| Creators | Kanani, Dharmeshkumar M. |
| Contributors | Ghosh, Raja, Chemical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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