Entrapment_Method For Enzyme Immobilization.ppsx
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Transcript Entrapment_Method For Enzyme Immobilization.ppsx
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KRRC Information Section
ENTRAPMENT
Enzymes are physically entrapped inside a matrix.
Bonds involved may be covalent or non covalent
Matrix used will be water soluble polymer
Generally entrapment does not involve a chemical or physical/chemical reaction
directly with enzyme molecules.
Physical adsorption on active carbon particles and ionic adsorption on ion exchange
resins are important for enzyme immobilisation
ENTRAPMENT
Form and nature of matrix varies
Pore size of matrix is adjusted to prevent the loss of enzyme
Possibility of leakage of low molecular weight enzymes
Agar and carragrenan have large pore sizes
Pore size can be adjusted with the concentration of the polymer
Methods of Entrapment
Inclusion in gels: enzymes are trapped in gels
Inclusion in microcapsules: enzymes entrapped in micromolecules formed
by monomer mixture such as calcium alginate, polyamine etc..
Polyacrylamide is the most widely used matrix for entrapping enzymes among the gels.
It is non-ionic
The properties of the enzymes are modified minimum in the presence of the gel matrix.
At the same time, the diffusion of the charged substrate and products is not affected.
Dimethylaminopropionitrile is the polymerisation initiator that is highly toxic
it must be handled with great care.
Calcium alginate does not depend on the formation of more permanent covalent bonds
between polymer chains
calcium ions cross-link the polymer molecules
beads formed in mild conditions, enzyme activity over 80% can be achieved
As calcium ions can be exchanged for sodium ions, similarly they can also be displaced
by other ions
care must be taken to ensure that the substrate solution does not contain high
concentrations of such ions that disintegrate the gel.
Entrapment method difficulties :
(i) leakage due to wide pore size of the gel [for example, agar, carrageenan, etc.
have large «10 microns)],
(ii) reduced substrate accessibility to the enzyme
(iii) some loss of activity due to the free radicals produced during
polymerization of the gel.
entrapment of enzymes has been widely used for sensing application
Cell entrapment is used for industrial production of amino acids such as Laspartic acid, L-malic acid etc.
Advantages
Disadvantages
Cheap (low cost matrix available)
Leakage of enzyme
Mild conditions required
Pore diffusion limits
Conformational change of
enzyme having less chance
ENCAPSULATION
enclosing of a droplet of solution of ezymein semipermeable membrane
capsule.
membrane may be polymeric, lipoidal, lipoprotein basednon-ionic in nature.
capsule is made up of cellulose nitrate and nylon
effectiveness largely depends on the stability of enzyme
Immobilization of enzymes and mammalian cells
Pancreatic cells grown in cultures immobilized by encapsulation
Three different ways of encapsulation on basis of
Specific membrane reactors
Formation of emulation
Stabilisation of emulation to form microcapsule
Encapsulation of enzyme in mesoporous silica spheres via immobilization
followed by assembling an organic/inorganic nanocomposite shell on the particle
surface leads to high loading enzyme activity and stability protection
proteolysis
from
Advantage
cheap
and simple
Large
quantities of enzyme can be immobilized
Disadvantages
Pore
size limitation
Only
small substrate molecule is able to cross the membrane