Page 394 - Academic Press Encyclopedia of Physical Science and Technology 3rd Chemical Engineering

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Encyclopedia of Physical Science and Technology EN009K-419 July 19, 2001 20:57

Membranes, Synthetic, Applications 329

phenomenal growth of this industry has also brought with
it new challenges in the areas of separation and purifica-
tion. Membrane technology offers a number of existing
solutions and promises new ones. In this section, the use
of membranes as tools in various stages of life science
research up to large-scale production of biopharmaceuti-
cals will be examined.
Certain special requirements apply to membrane sys-
tems used in the life sciences. Proteins, cells, and their
constituents retain their biological functions within a rel-
atively narrow range of environmental conditions. Many
are sensitive to provocation or damage when those condi-
tions change, or even upon contact with surfaces recog-
nized to be foreign. For these reasons, materials used to
separate or purify biological materials must be “biocom-
patible” to various extents, and process conditions estab-
lished to avoid irreversible changes in the desired product.
An entire area of study has emerged focused on the de-
velopment and optimization of biomaterials for different
purposes, including those used to prepare or modify syn-
thetic membranes.

A. Applications in Discovery and Research
Living systems are enormously complex in their compo-
sition and function. Understanding individual interactions
frequently begins with resolving, identifying, and quanti-
fying key components of interest. Many laboratory proce-
dures consist of steps aimed at recovering a single biolog-
FIGURE 43 Bipolar membrane processes for (a) SO 2 removal ical or biochemical entity in high purity. Microfiltration is
from stack gases; and (b) stainless steel pickling bath waste acid
regeneration. routinely used for separating particulates, cells, and cell
fragments from soluble proteins. Ultrafiltration has also
become the preferred procedure for desalting proteins,
by harsh conditions, unfavorable kinetics, catalyst poi- nucleic acids, or peptides. Proteins with different molecu-
soning, ineffective removal of inhibitory products or in- lar weights may also be fractionated. A common technique
termediates, and/or troublesome product recovery. Some for resolving protein mixtures is electrophoresis (q.v.), in
process concepts are shown in Table X. which a sheet of hydrogel carrying the protein mixture is
subject to an electrical field to cause differential migration
according to the charge characteristics of each component.
VI. BIOTECHNOLOGY AND LIFE SCIENCES At the conclusion of the electrophoretic separation, a mi-
croporous membrane is often applied (blotted) onto the
Over the past quarter century, biotechnology has fun- hydrogel to transfer the pattern of resolved proteins, nu-
damentally transformed the life sciences from operating cleic acids, and their fragments to a stronger substrate to
within the confines of nature to a point where manipu- facilitate further analysis or handling.
lation of the structure and behavior of life forms have Laboratory membrane applications usually involve
become both routine and commercially successful. Ad- small samples. Consistency and resolution of the separa-
vances in recombinant DNA technology, for example, tion is as important as productivity of the membrane. As
have enabled production of highly effective vaccines, an- is typical in analytical work, membranes or membrane
tibodies, growth hormones, and other biopharmaceuticals. devicesareusuallyusedonceanddiscarded.Strictcompli-
Even more recently, the Human Genome Project has be- ance to sterility and validation requirements is expected.
gun to yield important—if not yet complete—information Various technological advances have contributed to the
about the genetic origins of diseases, enabling extremely success to date of genomics, the deciphering and sys-
focused development of therapeutic countermeasures. The tematic investigation of genetic information embedded