TYPES OF BIOREACTORS

Aim: To study the set up of various types of bioreactors used in fermentation process.

Principle: A biochemical reactor is a vessel in which substrate undergoes a biochemical

transformation by the action of microorganisms or enzymes to form products. The

bioreactors are classified into three types depending upon the feeding mechanism:

a) Batch reactor: It is a type of reactor which is fed with all the reactants and contents

are sealed. There will not be any further inflow or out flow of materials. The products are

withdrawn after the reaction time is over. They are ideally suited for: small scale operations,

for testing new processes at R& D stage, for making some expensive products, processes

which cannot be translated into continuous operations.

b) Fed-batch/Semi-batch reactor: It is a type of batch culture which is fed sequentially

with medium without removal of culture fluid. A fed batch culture is established initially in

a batch mode and then can be fed according to one of the following feeding strategies:

1) Same medium used to establish the batch culture is added, resulting in an increase in

volume.

2) A solution of the limiting substrate at the same concentration as that in the initial

medium is added resulting in an increase in volume.

3) A concentrated solution of the limiting substrate is added at a rate less than in (1) and

(2) resulting in an increase in volume.

4) A very concentrated solution of the limiting substrate is added at a rate less than in

(1), (2) and (3) resulting in an insignificant increase in volume.

They are ideally suited for production of high cell densities due to extension of working time

and control over the production of by products or catabolite repression due to limited

provision of substrate.

c) Continuous reactors: It is a type of reactor in which the medium is fed continuously

and simultaneously the product is withdrawn. Two types of reactors are there: CSTR-

Continuous Stirred Tank Reactor and CPBR- Continuous Packed Bed Reactor. In the first

one the contents are thoroughly mixed with a stirrer while in the other contents fully mix the

moment they enter the reactor and then the concentration is uniform through the reactor.

Requirements:Conical flask, bioreactor column, separating funnel, beakers, glass wool,

magnetic stirrer, magnetic bead, forceps, glass rod, silicon tubing.