2. What Are Enzymes?
• A Catalyst is a substance that can be added to a reaction to
increase the reaction rate without getting consumed the
process.
• Most enzymes are Proteins (tertiary and quaternary
structures) Act as Catalyst to accelerates a reaction
• An additional non-protein molecule that is needed by some
enzymes to help the reaction
• Tightly bound cofactors are called prosthetic groups
• Cofactors that are bound and released easily are called
coenzymes
3. Advantages of Biocatalysts:
• Generally more efficient (lower
concentration of enzyme needed)
• More selective (types of selectivity:
chemo-selectivity, regio-selectivity,
diastereo-selectivity, and enantio-
selectivity)
• Enzymes act under mild conditions.
• Environment friendly (completely
degraded in the environment)
• Can be modified to increase
selectivity, stability, and activity
• More sustainable
• Enzymes can catalyze a broad
spectrum of reactions.
Disadvantages of
Biocatalysts :
• Susceptible to substrate or
product inhibition
• Limiting operating region
(enzymes typically
denatured at high
temperature and pH)
• Enzymes found in nature
in only one enantiomeric
form
• Phase contact limitation
4. Potentials of
Enzymes as
Catalysts in
Organic
Synthesis
Enzymes have unique complex three-dimensional structures
and the active site integrated therein
This enables a highly specific recognition of specific substrates
High to excellent chemoselectivity, the stereoselectivity as
well as regio-, diastereo- and enantioselectivity.
High conversion and selectivity : offer less E- factor
It is evident that enzyme catalysis requires specific suitable
reaction conditions such as pH, temperature and solvent,
which have to be considered in (bio-)process development.
5. Factor
affecting
catalytic
activity of
enzyme
• Enzyme Concentration: Product Concentration increases
with the increase of enzyme concentration.
• Effects of Inhibitors on Enzyme Activity: Enzyme
inhibitors are substances which alter the catalytic action
of the enzyme and consequently slow down, or in some
cases, stop catalysis.
There are three common types of enzyme inhibition –
competitive,
non-competitive and
substrate inhibition.
• Effects of pH: Enzymes are affected by changes in pH.
The most favorable pH value - the point where the
enzyme is most active - is known as the optimum pH.
6. Industrial Application of
Enzyme Biocatalysts:
• Enzymes are the most proficient catalysts, offering much
more competitive processes compared to chemical
catalysts.
• The number of industrial applications for enzymes has
exploded in recent years, mainly owing to advances in
protein engineering technology and environmental and
economic necessities.
7. DEMERITS
• Enzymes require narrow operation parameters.
• Enzymes display their highest catalytic activity in water.
• Enzymes may cause allergies.
• Often low specific activity.
• Instability at extreme temperatures and pH values.
• Availability for selected reactions only - long development
time for new enzymes.
8. What Is An Immobilized
Enzyme?
• An immobilized enzyme is one whose movement in space has been
restricted either completely or to a small limited region.
Why Immobilize Enzymes?
• Protection from degradation and deactivation.
• Re-use of enzymes for many reaction cycles, lowering the total
production cost of enzyme mediated reactions.
• Ability to stop the reaction rapidly by removing the enzyme from the
reaction solution.
• Enhanced stability.
• Easy separation of the enzyme from the product.
• Product is not contaminated with the enzyme.
9. IMMOBILIZATION TECHNIQUES
ADVANTAGES DISADVANTAGES
MORE STABILITY SOME ENZYMES BECOME UNSTABLE
HIGH ENZYME SUBSTRATE RATIO HIGH COST FOR ISOLATION,PURIFICATION AND
RECOVERY OF ACTIVE ENZYME
CONTINOUS USE AND LESS LABOUR INPUT USES IN INDUSTRIAL APPLICATIONS ARE LIMITED
IMPROVED PROCESS CONTROL LOSS OF CATALYTIC PROPERTIES IN SOME ENZYMES
LESS CHANCE OF CONTAMINATION IN PLANTS ENZYMES ARE INACTIVATED BY HEAT GENERATED
SYSTEM
12. ADSORPTION
• Involves the physical binding of the enzyme on the surface
of carrier matrix.
• Carrier may be organic or inorganic.
• The process of adsorption involves the weak interactions
like Vander Waal or hydrogen bonds.
• Carriers: - silica, bentonite, cellulose, etc.
• e.g. catalase & invertase
13. ENTRAPMENT
• In entrapment, the enzymes or cells are not directly
attached to the support surface, but simply trapped inside
the polymer matrix.
• Enzymes are held or entrapped within the suitable gels or
fibres.
• It is done in such a way as to retain protein while allowing
penetration of substrate. It can be classified into lattice and
micro capsule types.
14. ENCAPSULATION
It involves enclosing the
enzymes within semi -
permeable polymer
membranes e.g. semi
permeable collodion or
nylon membranes in the
shape of spheres.
• No chemical modification.
• Relatively stable forms.
• Easy handling and reusage
UNDER ADVANTAGE-
15. COVALENT BONDING
• Based on the binding of enzymes and water-insoluble carriers
by covalent bonds
• The functional groups that may take part in this binding are
Amino group, Carboxyl group, Sulfhydryl group, Hydroxyl
group, Imidazole group, Phenolic group, Thiol group, etc
• Disadvantages : covalent binding may alter the conformational
structure and active center of the enzyme, resulting in major
loss of activity and/or changes of the substrate
• Advantages : the binding force between enzyme and carrier is
so strong that no leakage of the enzymes occurs, even in the
presence of substrate or solution of high ionic strength.
16. CROSS LINKING
• Cross linking involves intermolecular cross linking of
enzyme molecules in the presence/absence of solid
support.
• The method produces a 3-dimensional cross linked enzyme
aggregate (insoluble in water) by means of a
multifunctional reagent that links covalently to the enzyme
molecules.
17. • Very little desorption(enzyme
strongly bound)
• Higher stability (i.e. ph, ionic &
substrate concentration)
Advantages of
cross linking:-
• Cross linking may cause significant
changes in the active site.
• Not cost effective.
Disadvantages
of cross
linking:-
18. PHASE TRANSFER
CATALYSIS
• Catalysis :-Catalysis is the process of increasing the rate of a
chemical reaction by adding a substance known as a
catalyst.
• Definition :- Phase transfer catalysis (PTC) refers to reaction
between two substances located in different immiscible
phases in the presence of catalyst.
• Heterogenous catalysis.
• It faciliate the migration of a reactant from one phase into
another phase where reaction occurs.
19. TYPES
• There are many types of phase transfer catalysts, such as
• quaternary ammonium
• phosphonium salts,
• crown ethers,
• cryptands, etc.
Among these, the quaternary ammonium salts are the cheapest and hence
the most widely used in the industry.
20. Some of the PTC’s normally used are:-
• Aliquat 336 : N+CH3(C8H17)3 Cl Methyl
trioctylammonium chloride
• Benzyl trimethylammonium chloride or
bromide (TMBA) N+(CH3)3 CH2 C6H5 X
• Benzyl triethylammonium chloride N+(C2H5)3
CH2 C6H5 X
• Cetyl trimethylammonium chloride or bromide
(CTMAB) N+ (CH3)3 (CH2)15 CH3 X-
21. THEORY OF CATALYST
1) Intermediate Compound formation theory (Homogenous catalyst reaction )
2) Adsorption theory ( Heterogenous catalyst reaction )
• Intermediate compound formulation theory: According to this theory one of the reactants
combines with catalyst to form intermediate product, which carries out the reaction, E.g.
A + C = AC
AC + B =AB + C
A + B + C = AB + C ,
where A and B are reactants, C is the catalyst and AC is the intermediate product
22. Adsorption Theory: In general adsorption theory applies to heterogeneous
catalytic reactions. The catalyst functions by the adsorption of the reacting
molecules on its surface. The adsorption reaction undergoes four types of
steps:
i) Adsorption of reactant molecule: The reactant molecules A and B
strike the surface of the catalyst. The reaction molecules held up by the
partial chemical bond.
ii ) Formation of intermediate complex: The reactant molecule adjacent
one another join to form an intermediate complex ( A-B ). The
intermediate complex is unstable.
23. iv ) Release of product: The product particles are released from the
surface.
iii ) Decomposition of intermediate complex: The intermediate
complex breaks to form the products C and D. The product
molecules hold to the catalyst surface by partial chemical bond.
24. APPLICATIONS
• PTC is widely exploited industrially
• Applications involving the use of a co-catalyst include co-catalysis by surfactants, alcohols and other weak acids in
hydroxide transfer reactions, use of iodide, or reactions carried out with dual PI catalysts have been also reported
• In nucleophilic substitution reactions and in reactions in the presence of bases involving the deprotonation of
moderately and weakly acidic organic compounds
• PTC has made possible the use of cheaper and easily available alternative raw materials like potassium carbonate
and aqueous NaOH solution, thereby obviating the need of severe anhydrous conditions, expensive solvents, and
dangerous bases such as metal hydrides and organometallic reagents
• When any kind of chemical reactions are carried out in the presence of a PT catalyst in biphasic systems, simple,
cheap and mild bases like NaOH and K2CO3 can be used instead of toxic alkali metal alkoxides, amides, and
hydrides
• Perfumery and Fragrance Industry like Synthesis of phenylacetic acid, an intermediate in the perfumery industry
• In the field of Pharmaceuticals like Synthesis of various drugs like dicyclonine, phenoperidine, oxaladine, ritaline,
etc.
25. REFERENCE
• Holum, J.: Elements of General and Biological Chemistry, 2nd ed., 377,
Wiley, NY (1968).
• Martinek, R.: Practical Clinical Enzymology: J. Am. Med. Tech., 31, 162
(1969).
• Harrow, B., and Mazur, A.: Textbook of Biochemistry, 109, Saunders,
Philadelphia (1958).
• Pfeiffer, J.: Enzymes, the Physics and Chemistry of Life, pg 171-173,
Simon and Schuster, NY (1954)
