Enzyme molecules are mixed
with the immobilising support
and bind to it due to a
combination of hydrophobic
interactions and ionic links
Adsorbing gents used include porous carbon, glass beads, clays and resins
Because the bonding forces are not particularly strong, some
enzymes can become detached.
However, provided the enzyme molecules are held so that their active site is not
changed and displayed, adsorption can give very high reaction rates.
Covalent bonding
Enzyme molecules are covalently bonded to a support, often by covalently
linking enzymes together to an absolute material (clay) using a cross-linking
agent like gluteraldehyde or sepharose.
This method does not immobilise a large
quantity of enzyme but binding is very strong
so there is very little leakage of enzyme from
the support.
Entrapment
Enzymes may be trapped in a bead network or in a cellulose fibre network.
However reaction rates can be reduced because substrate molecules need to get through the trapping barrier.
This means the active site is less easily available than with adsorbed or covalently bonded enzymes
The enzymes are trapped in their natural state.
Membrane separation
Enzymes may be physically
separated by a partially permeable
membrane.
Most simply, the enzyme solution is held at one
side of the membrane whilst substrate solution is
passed slong the other side.
Product molecules are small enough
to pass back through the membrane.
Substrate molecules are small enough to pass through the membrane so
that the reaction can take place.