Chemistry Reference
In-Depth Information
Fig. 4.1
Enzyme activity
viewed as a simple 'lock and
key' system
Substrate
Enzyme
feasible [
2
]. It is therefore of great interest to make use of enzymes efficiently on an
industrial scale. Indeed, presently, enzymes have found applications in biocatalysis,
textile manufacturing, food processing, syntheses of pharmaceuticals, cosmetics,
pollution control and anti-fouling coatings [
5
,
6
]. This diversity of their current ap-
plications strongly supports the importance of enzymes.
Enzymes do, however, have several inherent limitations that restrict full utilisa-
tion of their potential on a commercial scale. One such problem is their soluble
nature, which hinders the ease of enzyme recovery and reusability potential, and
can also lead to instability. Resultantly, expensive and energy intensive separations
are often necessary, and product contamination can be problematic. In addition, en-
zymes are often delicate and their molecular structure is prone to destruction under
processing conditions [
2
,
7
]. As a consequence, the 'lock and key' system can prove
problematic due to the deformation of the shape of the enzyme—the substrate will
no longer be able to attach to the active sites, therefore greatly reducing the effec-
tiveness of the system. High temperatures, extreme pH conditions and the presence
of other components such as organic solvents can all result in enzyme deformation
(as well as causing detrimental effects through other means such as complicating
chemistry). This therefore inhibits enzyme performance, and may even result in
complete denaturation [
3
,
4
,
8
].
4.2
Enzyme Immobilisation Overview
To overcome the problems associated with enzymes, considerable research has
been carried out on enzyme immobilisation techniques, whereby the enzymes are
effectively supported/confined for the duration of the reaction. This allows their
catalytic properties to be preserved and easier handling, while assisting with re-
peated and continuous use, therefore reducing operating costs [
2
-
4
]. Continuous
operation is also preferable for improved throughput and efficiency [
1
,
2
]. Effective
immobilisation has also been shown to result in greater enzyme stability over more
intense process conditions, such as more extreme temperatures and pH values, and
non-aqueous conditions, thereby expanding their potential applications. Reactor
design and control is also simpler for immobilised systems since the enzyme can
