The document describes the structure and components of a conventional bioreactor. A conventional bioreactor consists of a cylindrical reaction vessel surrounded by a cooling jacket. It contains a sparger at the bottom to introduce gases and an agitator shaft connected to a motor. Sensors for pH, temperature and dissolved oxygen are located on the side ports. Connections for adding chemicals are located above the liquid level. Common materials for construction include stainless steel. Key components are impellers for mixing, spargers for aeration, temperature control via a cooling jacket, and pH monitoring electrodes. After fermentation is complete, the bioreactor must be cleaned before the next use.

1. Conventional Bioreactor:
 By
 Aswartha Harinath Reddy
 Department of Biotechnology
 Christ University

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4. Structure of Conventional bioreactors :
Factors considered for designing a bioreactor.
 Conventional bioreactors are cylindrical vessels with domed top
and bottom.
 The reaction vessel, surrounded by a cooling jacket and provided
with a sparger at the bottom.
 The air (or other gases such as CO2and NH3 ) can be introduced
through the sparger.

5.  The agitator shaft is connected to a motor at the bottom.
 The reaction vessel has side ports for pH, temperature and
dissolved O2 sensors.
 Above the liquid level of the reaction vessel, connections for acid,
alkali, antifoam chemicals and inoculum are located.

6.  The bioreactor vessel is usually made up of stainless steel.
 The materials used for the construction of bioreactor must be
non-toxic and must withstand the repeated sterilization with
high pressure steam.
 The bioreactor is usually designed to work at higher temperature
(150-180°C), higher pressure.

7. Aspect ratio:
 The aspect ratio of bioreactor describes the proportional
relationship between height and width (Diameter).
 The size of the bioreactor i.e height and width of bioreactor
referred as Aspect ratio.
 The aspect ratio of stirred tank bioreactor is 3:5.

8. Components of the fermenters:

9. Impellers or Agitators:
 This facilitates the mixing of the contents of the reactor which
keeps the “cells” in the perfect homogenous condition.
 It provide transport of nutrients and oxygen to cells to produce the
desired products.

10. Speed of Impellers:
 The speed of the impellers determines the stirring rate in a
fermenter.
 The maximum speed of the impellers is around 60-120 rpm in 450
liters fermenter.

11. Types of Impellers:
 Propellers:
 Turbines:
 Paddles:

12. Propellers:
 The marine propeller is a relatively
small and high speed impellers.
 Widely used in low viscosity
liquid systems.
 Speed of rotation will vary from
400 rpm to 1000 rpm.
It has a high rate of flow displacement and
generates strong currents in an axial direction.

13. Turbines:
 A flat blade turbine (FBT) impeller is widely used in many
submerged microbial reactions.
 A turbine consists of several straight blades mounted vertically
on a flat plate.
 Turbines are moderate speed impellers and fluid flow is generated
in a radial and tangential directions.

14. Paddles:
 In Paddle impellers straight blades mounted vertically on a long,
horizontal shaft.
 These impellers run at a slow to moderate speed (2 to 150 rpm).
 Used to mix high viscosity liquids.
 Radial and tangential currents are generated during rotation of
paddles.

15. Aeration:
 The bioreactor gets aerated by the supply of O2.
 Aeration performed by bubbling air through spargers.
 A sparger is a tool used for introducing air into the fermentation
medium.

16. Three basic types of sparger:
 1. The porous sparger,
 2. The orifice sparger (a perforated pipe)
 3. The nozzle sparger (an open or partially closed pipe).

17. Porous Sparger:
 The porous sparger is mainly used for laboratory scale non
agitated fermenter.
 It is made up of glass, ceramics or metal.

18. Orifice Sparger :
 Used in small stirred fermenters.
 The perforated pipes were arranged below the impeller in the
form of rings (ring sparger).


19. Nozzle Sparger:
 Nozzle spargers used in laboratory to industrial scale bioreactors.
 Nozzle spargers have a single open or partially closed pipe.
 Ideally the pipe should be positioned centrally below the impeller.
 The single-nozzle sparger normally does not get blocked.

20. Temperature regulation
 There are two temperature ranges to run the fermentations a
mesophilic range (20-45°C) and a thermophilic range (> 45°C).

21. Cooling Jacket :
 The jacket provides the annular area for circulation of constant
temperature water.
 Which keeps the temperature of the bioreactor at a constant
value.
 Desired temperature water is constantly circulated in to jacket
to maintain a particular temperature in the bioreactor.

22. pH monitoring
 The electrodes or pH probes used to monitor pH of
bioreactors.
 The electrodes or pH probes withstand high TMP and
Pressure.
 Combination of electrodes reference and glass electrodes are
used.

25. Antifoaming agents.
 A an anti-foaming agent is a chemical additive that reduces the
formation of foam in industrial process liquids.
 A foam is formed by trapping pockets of gas in a liquid or
solid.

26.  Vegetable & Animal Oil
 Castor Oil
 Silicones Oil

27.  Agitation and aeration is one of the reason for the formation of
foam.
 During anaerobic fermentation of sugar produce CO2 is the
end product.

30. Cleaning of Bioreactor:
 As the fermentation is complete, the bioreactor is harvested i.e. the
contents are removed for processing.
 The bioreactor is then prepared for the next round of
fermentation after cleaning (technically called turn round).
 The time taken for turn round referred to as down time should
be as short as possible (since it is non-productive).

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