Transcript Entrapment_Method For Enzyme Immobilization.ppsx

Teaching Aids Service by
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