NAMS 2002 Workshop - ICOM 2008

Biomedical and Biotechnology II – 1 – Keynote
Wednesday July 16, 9:30 AM-10:15 AM, Honolulu/Kahuku
Macroporous Membrane Adsorbers: Correlations between Materials
Structure, Separation Conditions and Performance in Bioseparations
M. Ulbricht (Presenting), Lehrstuhl für Technische Chemie II, Universität Duisburg-Essen,
Germany - mathias.ulbricht@uni-due.de
J. Wang, Lehrstuhl für Technische Chemie II, Universität Duisburg-Essen, Germany
F. Dismer, Institut für Biotechnologie, Forschungszentrum, Jülich, Germany
E. von Lieres, Institut für Biotechnologie, Forschungszentrum, Jülich, Germany
J. Hubbuch, Institut für Biotechnologie, Forschungszentrum, Jülich, Germany
Separations with membrane adsorbers are a very attractive and rapidly growing
field of application for functional macroporous membranes [1,2]. The key
advantages in comparison with conventional porous adsorbers (particles,
typically having a diameter of >50 µm) result from the pore structure of the
membrane which allows a directional convective flow through the majority of the
pores; thus, the characteristic distances (i.e., times) for pore diffusion will be
drastically reduced. The separation of substances is based on their reversible
binding on the functionalized pore walls; the most frequently used interactions
are ion- exchange and various types of affinity binding. However, there is still a
large interest in improvement of performance for established membranes and in
development of novel membranes with higher selectivity [2]. Further, for a better
understanding of the complex interplay between mass transfer and reversible
binding, a more comprehensive analysis of the (coupled) influences of pore
structure and functional binding layer as well as their interactions with the mobile
phase, all as function of flow rate, is strongly needed. Here we will present our
recent efforts to elucidate influences of the materials and the process conditions
onto resulting separation performance.
First, a detailed analysis of pore structure and protein binding in commercial
cation-exchange membrane adsorbers (Sartobind®) by conventional and
environmental scanning electron microscopy (ESEM) as well as confocal laser
scanning microscopy (CLSM) has been performed [3]. The binding of mono-Cy5labelled
lysozyme inside fluoresceine-labelled and unlabelled Sartobind®
membranes was monitored by CLSM. The characteristic fluorescence intensity
distributions indicated that protein binding takes place predominately in a layer
which is anchored to a fine cellulose fiber network. Due to the limited thickness of
this binding layer, a significant fraction of the macropores remained free of
protein. Protein binding as function of concentration and incubation times was
also monitored by CLSM and discussed related to the binding isotherms for the
membranes. For the first time, the binding and breakthrough of (dye-labelled)
protein within a (dye-labelled) membrane adsorber has been monitored in situ
and on-line by using CLSM. Distinctly different breakthrough times have been