Chemistry Reference
In-Depth Information
Chapter 4
Bioinspired Silica for Enzyme Immobilisation:
A Comparison with Traditional Methods
Claire Forsyth and Siddharth V. Patwardhan
4.1
Introduction to Enzymes
In recent years, it has become necessary to investigate the feasibility of more envi-
ronmentally friendly or '
green
' process routes. This is largely due to increasingly
stringent environmental regulations, environmental concerns, and drives for greater
efficiency [
1
]. Compared with traditional routes, green routes typically involve
lower temperatures, therefore reducing energy costs, and minimise the use of any
toxic materials or the production of harmful waste. These can greatly reduce operat-
ing costs (such as handling and waste treatment), and by making an efficient use
of resources, process efficiency—and therefore economics—can be improved [
2
].
A key area of green route investigation is in the application of biocatalysts. Bio-
catalysts are defined as biological substances which can act as catalysts to chemi-
cal reactions. Their description is not confined solely to enzymes, and can include
cellular organelles (a sub-unit with a cell), microbes, and plant and animal cells
[
3
,
4
]. Due to their ubiquitous nature, enzymes have largely been focused on in
studies, and resultantly, the terms 'enzyme' and 'biocatalyst' are commonly used
synonymously
A simplified explanation of how enzymes work is the 'lock and key' hypothesis.
From this, only a specific substrate can fit into active sites on the enzyme to form an
enzyme-substrate complex (Fig.
4.1
). This complex therefore makes the substrate
in a better position for reacting, resulting in a lower activation energy, and therefore
leading to greater reaction rates. Enzymes are thus advantageous due to their reac-
tant (substrate) specific catalysis, reduction in by-product formation and their inher-
ent ability to catalyse reactions under mild conditions. This can therefore reduce
operating costs and safety implications; they also improve the green credentials of
processes. In some cases, enzymes can even make otherwise unattainable reactions
