Enzyme_reactors-application in Biotechnology

DEFINITION
Enzyme reactors are vessels employed to carry out the desired
conversion of raw materials using enzymes.
Enzymes may be immobilized or not during the process.
Enzyme immobilization is the process of confining the enzyme
molecules to a solid support over which a substrate is passed and
converted to products.
The aim of an enzymatic reactor is to allow enzyme and substrate to
come into contact for a sufficient period of time for reaction to take
place; enzyme and product may then easily be separated.

TYPES OF ENZYME REACTORS
Batch reactors
Continuous Flow Reactors

BATCH REACTORS
 Essentially large agitated tanks in which enzyme and substrate are placed.
The reaction is allowed to progress to its end after which the reactor is drained
and the product is separated from the enzyme
If soluble enzyme is employed, it is normally separated by subsequent
denaturation (i.e. by heat treatment)
 Suitable with cheap enzymes
Costly enzymes can be used also when immobilized and recovered by
centrifugation or filtration
Risk of enzyme destruction during recovery process
Use of immobilized enzymes has limited potential in batch reactors

TYPES OF BATCH REACTORS
Stirred tank for soluble enzymes
 Stirred tank for immobilized enzyme
 Stirred tank with immobilized basket paddles
 Stirred tank with immobilized enzyme basket baffles
Total recycle packed bed reactor
 Total recycle fluidized bed reactor

CONTINUOUS-FLOW REACTORS
 Principle behind this reactor is the continuous addition of
addition of substrate and exit of product from the reactor.
 Subtypes:
 continuous-flow stirred-tank reactor
 packed-bed reactors
 hollow-fiber reactor
 Fluidized-bed reactors

CONTINUOUS STIRRED TANK REACTOR
It consists of a stirred tank with a separate substrate inlet
and reactor mix (i.e. product) outlet
 By careful choice of size of the tank, enzymatic activity
and rate of addition of substrate, the percentage of
conversion of substrate into product can be adjusted as
desired.
E.g.: a low flow rate, a large reactor size (and hence long residence
times) and high enzymatic activity will give high product yields

CONTINUOUS STIRRED TANK REACTOR
CTN
The immobilized enzyme may be kept inside the reactor by
 filtration of the stream of product, incorporating a subsequent
settling stage, by immobilizing the enzyme on magnetically
active particles and retaining it in a magnetic field (which also
serves to stir the particles) or
 by immobilizing the enzyme to the paddles of the agitator shaft
Possibility of combination with an ultrafiltration process
which permits the use of soluble immobilized enzymes in the
reactor in case of soluble or colloidal substrate

PACKED-BED REACTORS
• Here the catalyzer(enzymes) is packed into a column and to make the
substrate flow through the column in such a way that the product is obtained
at the outlet.
• Ideal when the flow rate profile across a transverse cross section of the
column is perfectly flat; systems like this are known as plug-flow reactors
• The column can be constructed as a tall column or a fiat bed
• The degree of reaction, for a fixed flow rate, is proportional to the length of
reactor column

• When substrate is added through the upper part of the column the
particles of catalyst then tend to jam together, plugging the column
• the enzyme may be immobilized onto a membrane or a sheet of
material (ie a paper filter) and confined in a filter-press
arrangement
• Diameter of immobilized enzyme pellets: 1-3mm
• Use pellets of uniform size and in an upward flow of substrates.
• Matrix used is fairly rigid

DISADVANTAGES OF PACKED-BED
REACTORS
• Packed bed reactors may become clogged
up by colloids or precipitates present in the
reaction mixture.
• Temperature or pH is not easily regulated
especially in reactors of >15 cm diameter.
• Channels may form in the reactor bed due
to excessive pressure drop, irregular
packing or uneven flow stream

VARIATIONS OF PACKED-BED REACTORS

HOLLOW FIBER REACTORS
• They are thick-walled tubes about the diameter of a human hair.
• The tubes are made of semipermeable material, such as cellulose, which
confines large molecules (enzyme) while allowing free passage of small ones
(substrate and product).
• Hollow fibers are packed into a column. The enzyme can be retained in the
interior of the fibers and the stream of substrate passes round the outside of
them.
• The substrate will diffuse through the wall of the fiber, reacting with the
enzyme: the product can diffuse back through the wall of the fiber to the flow
stream.
• Alternatively, it is possible to pass the substrate through the centre of the fiber

ADVANTAGES OF HFR
Easy setup, reduced oversight
Small size
Low cost
High product concentration
Reduced capital costs
Widely used in hybridoma technology

FLUIDIZED BED REACTORS
They are a hybrid of continuous flow- stirred tank and packed-bed
reactors.
 The immobilized enzyme is loosely packed into a column and the stream
of substrate passes from the lower to the upper part of the column at a
fixed rate which is sufficiently high to lift and mix the particles of
immobilized enzyme within the column.
 Because the particles of immobilized enzyme are denser than the
reaction medium they remain in the lower part of the column, unless the
flow rate is so high that the particles of enzyme can be transported to its
upper part.

 In this way when the substrate is introduced into the
column as a flowing stream, the bed of solid particles is
transformed into a fluid-like state making the particles of
immobilized enzyme separate and move about in the
column.
The column acquires the appearance of a gently boiling
liquid. This effect is quite efficient at mixing catalyst with
substrate

APPLICATIONS OF ENZYME REACTORS
• Bioconversion of complexes substances using immobilized
enzymes
• Protein analysis
• HPLC
• Industrial applications: Synthesis and/or modification of
antibiotics, steroids and hormones, vitamins, amino acids,
organic acids, radioactive compounds
• Analytical and medical applications

REFERENCES
 Applications of Immobilized Enzymes ,MANUEL G ROIG,* J FELIPE
BELLO, FERNANDO G VELASCO, CARMEN D DE CELIS and JUAN M
CACHAZA
 www.rpi.edu/dept/chem-eng/Biotech-Environ/IMMOB/typesofreactors.html
 http://hollow-fiber.com/2015
 www.wikipedia.com
 www.google.com/images

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