Types of Reactors
In an enzyme reactor, the highest specific enzyme activity is desirable. It is considered an added bonus if the support that is used also aides in separation. One approach is to use a molecular sieve as the support and pulse the reactor bed with the alternating passage of substrate solution and water. The result is that bands of unused substrate and product progress down the column. It so happens that the enzymes for which this technique would be useful are also those which in some cases benefit in having the enzyme immobilized on a porous support.
For an industrial reactor,
it is preferable to use supports that are non-biodegradable such as glass,
silica, Celite, Bentonite, alumina, or titanium oxide, if possible. Even
the linkages between enzyme and support can be non-biodegradable, as they
are in the case of titanium. In some of these supports the physical nature
of the surface becomes a major problem. Thus, some supports that form excellent
packed beds fail to do so when coated with enzyme. Particles which ideally
self-suspend in a fluid bed may form aggregates during use which will require
more power to pump through substrate. Many problems were encountered using
porous glass supports until someone realized that the glass itself could
dissolve. This problem has been eliminated by treatment of the glass surface
with zirconium.