Fermenters, also known as bioreactors, are specially designed vessels used for growing microorganisms in a controlled environment. They allow microorganisms to grow in large volumes of highly nutritive culture media and convert feed into the desired end product through fermentation. Fermenters must provide optimal conditions for growth and production while minimizing power consumption and contamination risks. They consist of components like the fermenter vessel, heating/cooling system, aeration system, agitator, sparger, baffles and controls for monitoring environmental factors. Common types of fermenters include stirred tank, airlift, tower and bubble cap designs which utilize different mechanisms for mixing and oxygenating the culture broth.

1. FERMENTERS
PREPARED BY:
Bhargavi Mistry
[M. Pharm (Pharmaceutics)]

2. 01 Introduction
LIST OF CONTENT
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02 Functions Fermenter
03 Design of fermenter 04 Types of fermenter

3. INTRODUCTION
Fermentation:
Fermentation:
➢ Fermentation is defined as growing culture of microorganisms in a nutrient media
and converting feed into the desired end product.
➢ It is described as a biochemical reaction in which microorganisms serve as biocatalysts.
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Fermentors/Bioreactors:
Fermentors/Bioreactors:
➢ The most articulate, manipulative and progressive industrial (commercial) usage of
microorganisms invariably needs that they be allowed to grow in large vessels
essentially loaded with considerable quantum of highly nutritive culture media. These
specially designed vessels are universally and commonly termed as fermentors or
bioreactors.

4. FUNCTIONS OF FERMENTERS
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1) It should provide a controlled environment for optimum biomass/product yield.
2) It should permit aseptic fermentation for a number of days reliably.
3) It should provide adequate mixing and aeration for optimum growth and
production, without damaging the microorganisms/cells.
4) The power consumption should be minimized.
5) It should provide easy and adaptable temperature control.
6) Facility of sampling should be provided.
7) It should have a system for monitoring and regulating pH of fermentation broth.
8) Evaporation losses should be minimum.
9) Minimum labour maintenance.
10) Construct using the cheapest material.

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Figure: Diagram of the fermenter
DESIGN OF FERMENTERS

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1) Fermenter Vessel 7) Sealing Assembly
2) Heating and Cooling Apparatus 8) Feed Ports
3) Aeration System 9) Foam-Control
4) Agitator (impeller) 10) Valves
5) Sparger 11) Controlling Devices for
Environmental Factors
6) Baffles 12) Use of Computer in Fermenter
➢ The fermenter contains the following components:
Component of fermenter:
Component of fermenter:

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1) Fermenter Vessel
➢ A fermenter is a large cylinder closed at the top and bottom connected with
various pipes and valves.
➢ The vessel is designed in such a way that it allows it to work under controlled
conditions.
➢ Glass and stainless steels are two types of fermenter vessels used.
➢ The glass vessel is usually used in small-scale industries. It is non-toxic and
corrosion-proof.
➢ Stainless steel vessel is used in large-scale industries. It can resist pressure and
corrosion.

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2) Heating and Cooling Apparatus
➢ The fermenter vessel’s exterior is fitted with a cooling jacket that seals the vessel
and provides cooling water.
➢ Thermostatically controlled baths or internal coils are generally used to provide
heat while silicone jackets are used to remove excess heat.
➢ A cooling jacket is necessary to sterilize the nutrient medium and remove the
heat generated during fermentation in the fermentor.

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3) Aeration System
➢ An aeration system is one of the very important parts of a fermenter.
➢ It is important to choose a good aeration system to ensure proper aeration and
oxygen availability throughout the culture.
➢ It contains two separate aeration devices (sparger and impeller) to ensure proper
aeration in a fermenter.
➢ The stirring accomplishes two things:
➢ It helps to mix the gas bubbles through the liquid culture medium and
➢ It helps to mix the microbial cells through the liquid culture medium, ensuring
the uniform access of microbial cells to the nutrients.

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4) Agitator (Impeller)
Agitators achieve the following objectives:
➢ Bulk fluid and gas phase mixing
➢ Air dispersion
➢ Oxygen transfer
➢ Heat transfer
➢ Suspension of solid particle
➢ Maintenance of uniform environment throughout the vessel.

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1) Disc turbine:
Disc turbine consists of a disc with a series of rectangular vanes set in a vertical
the plane around its peripheri.
2) Vaned discs turbine:
The vaned discs turbine has a series of rectangular vanes attached vertically to
the underside of the disc.
3) Open turbines of variable pitch
In this type of turbine, the vanes are attached directly to a boss on the agitator
shaft.

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5) Sparger
➢ A sparger is a system used for introducing sterile air to a fermentation vessel. It
helps in providing proper aeration to the vessel.
➢ The sparger pipes contain small holes of about 5-10 mm, through which
pressurized air is released.
➢ Three types of sparger are used
1) Porous sparger
2) Nozzle sparger
3) Combined sparger–agitator

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6) Baffles
➢ There are four baffles that are present inside of an agitated vessel to prevent a
vortex and improve aeration efficiency.
➢ Baffles are made up of metal strips roughly one-tenth of the vessel diameter and
attached to the wall.
➢ The agitation effect is slightly increased with wider baffles but drops sharply
with narrower baffles.

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7) Sealing Assembly
➢ The sealing assembly is used for the sealing of the stirrer shaft to offer proper
agitation.
➢ There are three types of sealing assembly in the fermenter:
1) Packed gland seal
2) Mechanical seal
3) Magnetic drives

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8) Feed Ports
➢ They are used to add nutrients and acid/alkali to the fermentor.
➢ Feed ports are tubes made up of silicone.
➢ In-situ sterilization is performed before the removal or addition of the products.
9) Foam control
➢ The level of foam in the vessel must be minimized to avoid contamination, this is
an important aspect of the fermentor.
➢ Foam is controlled by two units, foam sensing, and a control unit.
➢ A foam-controlling device is mounted on top of the fermentor, with an inlet into
the fermentor.

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10) Valves
➢ Valves are used in the fermenter to control the movement of liquid in the vessel.
➢ There are around five types of valves are used, that is,
1) globe valve,
2) butterfly valve,
3) a ball valve, and
4) diaphragm valve.
5) A safety valve

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11) Controlling Devices for Environmental Factors
➢ A variety of devices are utilized to control environmental elements like
temperature, oxygen concentration, pH, cell mass, essential nutrient levels, and
product concentration.
12) Use of Computer in Fermenter
➢ For an efficient process, monitoring, and data collecting, fermentors are generally
coupled with modern automated and semi-automated computers and databases.

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TYPES OF FERMENTERS
Stirred tank fermenter
Airlift fermenter
Tower fermenter
Bubble up fermenter
01
02
03
04

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Stirred tank fermenter
➢ These are usually made of ‘glass’(smaller vessels) or ‘stainless steel’ (larger
volumes) vessels.
➢ These are closed systems having rather definite fixed volumes and are normally
agitated with motor-driven stirrers with lots of variation in design
specifications,
• Curved-bottom for more efficient mixing at low speeds
• Water-circulated jacket in place of heater-type (electrical) temperature control
• Mirrored internal finishes to minimize cell-damage

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Stirred tank fermenter

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➢ Several heteroploid cell lines may be grown successfully in such vessels.
➢ Small-scale reactors (cap. 2-50 L) fulfill the need for research biochemicals from
cells.
➢ Large-scale reactors (cap. 100-5000 L) are largely employed for growing
hybridoma cells for the production of monoclonal antibodies (MABs)
Advantages:

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➢ The cultures in air-lift type fermentors are subjected to ‘aeration’ and ‘agitation’ by
passing sterilized compressed air bubbles introduced strategically at the bottom of the
vessel.
➢ The fermentors have an inner draft tube via which the air bubbles as well as the
aerated medium rise because this effectively gives rise to the thorough mixing of the
culture and aeration simultaneously.
➢ The air bubbles being lighter lift to the top of the medium and the air subsequently gets
released through on outlet.
➢ Air-lift type fermentors with a capacity of 2-90L are invariably available for large-
scale production. However, 2000L fermentors are being employed specifically for the
production of monoclonal antibodies (MABs).
Air lift fermenter

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Figure: Diagram of the air lift fermenter

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➢ A tower fermenter has been defined by Greenshields and co-workers
➢ It is an elongated non mechanically stirred fermenter.
➢ This fermenter is designed to provide the best feasible and possible growth and
biosynthesis conditions for industrially vital microbial cultures.
➢ It should be strong enough to hold a large volume of the aqueous medium.
➢ It should not be either corroded by the fermentation product or even contribute
severe toxic ions to the prevailing growth medium.
Tower fermenter

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➢ The oxygen is readily and adequately available to the microorganism, and the
resulting CO2 obtained from the ‘microbial metabolism’ is mostly flushed out from
the medium accordingly through a vent provided at the top-end of the tower
bioreactor.
➢ The sample is introduced into the tower bioreactor from the bottom, and the
finished fermented product is removed from the top-end outlet as and when
required.

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Figure: Diagram of the tower fermenter

27. ➢ It essentially comprises a tank provided with a series of horizontal plates.
➢ Each plate supports a nutrient medium devoid of a carbon source, and subsequently,
the medium is duly inoculated with the ‘required microorganism’.
➢ Each plate is provided with several short vertical pipes that are strategically
connected to its upper surface, and duly projecting just above the surface of the
liquid culture medium.
➢ Each short vertical pipe has two important provisions, namely :
(a) A hole in the bottom of this pipe allows legitimate contact with the
atmosphere above the medium in the next immediate lower plate; and
(b) The top of the lower rim of the inverted cap extends beneath the surface of
the nutrient medium.
Bubble cap fermenter
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Figure: Diagram of the bubble cap fermenter

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REFERENCES
1) B. D. Singh, Biotechnology expanding horizons, Fourth revised edition 2012,
Kalyani publishers, Page no. 522-533
2) Ashutosh kar, Pharmaceutical biotechnology, reprint 2008, New age international
limited publishers, Page no. 186, 192-194, 198-201

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THANK YOU