248
11 Enzymes
It is noted that the process of recovery of the enzymes from the solid mass following cultivation of the microbes or homogenization of plant and animal biomass
is quite similar. The common goal is therefore to free up the proteins and then isolate
the desired enzymes.
11.6 Immobilization of Enzymes
Since enzymes are biological catalysts, they do not take part in the actual reaction
or biochemical process, they serve as surfaces for substrates to attach, and once
the process is complete, the enzymes are released and become available again. In
industrial processes, the enzymes need to be recovered and stored in a suitable form
for reuse. This is achieved by immobilizing the enzyme. Enzymes are mostly proteins which are soluble in water. This makes their recovery quite challenging after
a process; evaporation or crystallization at high temperature is not an option since
most enzymes are denatured or completely destroyed at temperatures about ~45 °C.
Immobilization of enzymes therefore entails converting them into insoluble forms
which can be more effectively collected, stored and reused. This can be achieved by
chemical or physical immobilization process (Dutta 2008). Other than being a source
of enzymes, aquatic organisms are also used in the immobilization of enzymes and
these are also discussed within the section.
Whole cells of enzyme-producing organisms can also be immobilized with the
activity of the enzyme and organisms remaining active. Although the use of immobilized enzymes and biological catalysts is at industrial scale which is still at infancy
(Moreno-Garcia et al. 2018), immobilized enzymes offer benefits such as avoiding
the live organism or enzyme from getting into the final product and cost savings.
Whole algae cells of N. muscorum, for example, can be immobilized in sodium alginate. When immobilized in 2% alginate at 30 °C, a concentration of 0.5 g/L and a
stirring rate of 100 rpm, the cells retained their activity even after five cycles of use.
The algal cells also showed higher yield in the immobilized form compared to when
used in their free form to catalyze the bioconversion of androst-4-ene-3,17-dione
to testosterone (Arabi et al. 2010). The rest of this section discusses the different
enzyme immobilization techniques, and in the process, some biopolymer used in
enzyme immobilization is also discussed.
11.6.1 Chemical Immobilization
The chemical immobilization process can be done by covalently bonding the vacant
functional groups on the enzymes to insoluble supports. These supports could be
monomers which are then copolymerized with the enzymes. Chemical immobilization can also be achieved through cross-linking the enzyme with multifunctional
11 Enzymes
It is noted that the process of recovery of the enzymes from the solid mass following cultivation of the microbes or homogenization of plant and animal biomass
is quite similar. The common goal is therefore to free up the proteins and then isolate
the desired enzymes.
11.6 Immobilization of Enzymes
Since enzymes are biological catalysts, they do not take part in the actual reaction
or biochemical process, they serve as surfaces for substrates to attach, and once
the process is complete, the enzymes are released and become available again. In
industrial processes, the enzymes need to be recovered and stored in a suitable form
for reuse. This is achieved by immobilizing the enzyme. Enzymes are mostly proteins which are soluble in water. This makes their recovery quite challenging after
a process; evaporation or crystallization at high temperature is not an option since
most enzymes are denatured or completely destroyed at temperatures about ~45 °C.
Immobilization of enzymes therefore entails converting them into insoluble forms
which can be more effectively collected, stored and reused. This can be achieved by
chemical or physical immobilization process (Dutta 2008). Other than being a source
of enzymes, aquatic organisms are also used in the immobilization of enzymes and
these are also discussed within the section.
Whole cells of enzyme-producing organisms can also be immobilized with the
activity of the enzyme and organisms remaining active. Although the use of immobilized enzymes and biological catalysts is at industrial scale which is still at infancy
(Moreno-Garcia et al. 2018), immobilized enzymes offer benefits such as avoiding
the live organism or enzyme from getting into the final product and cost savings.
Whole algae cells of N. muscorum, for example, can be immobilized in sodium alginate. When immobilized in 2% alginate at 30 °C, a concentration of 0.5 g/L and a
stirring rate of 100 rpm, the cells retained their activity even after five cycles of use.
The algal cells also showed higher yield in the immobilized form compared to when
used in their free form to catalyze the bioconversion of androst-4-ene-3,17-dione
to testosterone (Arabi et al. 2010). The rest of this section discusses the different
enzyme immobilization techniques, and in the process, some biopolymer used in
enzyme immobilization is also discussed.
11.6.1 Chemical Immobilization
The chemical immobilization process can be done by covalently bonding the vacant
functional groups on the enzymes to insoluble supports. These supports could be
monomers which are then copolymerized with the enzymes. Chemical immobilization can also be achieved through cross-linking the enzyme with multifunctional