A fermentor, also known as a bioreactor, is a closed vessel used for commercial fermentation processes. It provides controls for factors like temperature, pH, aeration and agitation to maintain optimal conditions for microbial growth. Early large-scale fermentors had capacities over 20 liters and were used to produce products like yeast and acetone. Modern fermentors can be designed as various types depending on the application, including stirred tank, airlift, photo and fluidized/packed bed bioreactors. Proper design of components like the vessel material, agitator, sparger and temperature/pH controls is important for efficient fermentation.

1. FERMENTOR/BIOREACTOR

2. Fermentor
• A fermentor (bioreactor) is a closed vessel with
adequate arrangement for aeration, agitation,
temperature and pH control, and drain or
overflow vent.
• A fermentor is used for commercial production in
fermentation industries.
• De Beeze and Liebmann (1944) used the first
large scale (above 20 litre capacity) fermentor for
the production of yeast.
• Chain Weizmann (1914-1918) developed a
fermentor for the production of acetone.

6. Design
A bioreactor should provide for the following:
(i) Agitation (for mixing of cells and medium),
(ii) Aeration (aerobic fermentors); for O2 supply,
(iii) Regulation of factors like temperature, pH,
pressure, aeration, nutrient feeding, liquid level
etc.,
(iv) Sterilization and maintenance of sterility,
and
(v) Withdrawal of cells/medium (for continuous
fermentors).

7. • The size of fermentors ranges from 1-2 litre laboratory
fementors to 5,00,000 litre or, occasionally, even more,
fermentors of upto 1.2 million litres have been used.

9. FACTORS TO DESIGN A FERMENTER
• The vessel should be well equipped to maintain aseptic
conditions inside it for a number of days.
• Aeration and agitation are important for the
production of biological metabolites. However,
controlled agitation is required to prevent any damage
to the cells.
• It should be less expensive in terms of power
consumption.
• Temperature is an important environmental factor
required for microbial growth. Therefore, a
temperature control system is required.
• Optimum pH is important for the growth of the
organism; therefore, the fermenter must be equipped
with a pH controller.

10. • The fermentation of a huge culture is a time-
consuming process. It needs to be contamination-
free until the process is complete. Apart from
that, it is also important to monitor the growth
rate of the organism. Therefore, an aseptic
sampling system is needed to design a fermenter.
• The fermenter vessel should be designed
properly to minimize the labor involved in
cleaning, harvesting, etc.
• It should be designed in such a way that it
reduces evaporation.
• The vessel needs to be equipped with a smooth
internal surface to support adequate mixing.

11. DESIGN OF FERMENTER
Hence design of a fermenter is important in the
process of fermentation.
• Construction material
• Agitator
• Stirrer
• Sparger
• Baffles
• Temperature control
• pH control

12. Construction material
• It is important to select a material for the body of
the fermenter, which restricts the chances of
contamination.
• It needs to be non-toxic and corrosion free.
• Glass is a material that provides a smooth surface
inside the vessel and also non-toxic in nature and
used in small scale production.
• In a pilot-scale fermenter normally the steel
contains around 10-13% of chromium
• In many cases nickel is also mixed in high
concentration with the chromium to make the
steel more corrosion resistant

13. Inoculation Port
• Inoculation port is a device from which
fermentation media, inoculum and substrate are
added in the fermentation tank.
Sampling point
• Sampling point is used for time to time
withdrawal of samples to monitor fermentation
process and quality control.
Bottom drainage port
• It is an aseptic outlet present at the bottom of
fermentor for removal of fermented media and
products formed.

14. Agitator or Impeller
• The impeller used in fermenters are bulk fluid
and gas mixing, air dispersion, heat transfer,
oxygen transfer, suspension of solid particles and
maintain the uniform environment inside the
vessel.
• Air bubbles often cause problems inside the
fermenter. Impellers involved in breaking the air
bubbles produced in a liquid medium.
• There are mainly three types of agitators used in
industrial-scale bioreactors namely disc turbine,
vaned disc and pitch open turbine.

17. Stirrer
• The stirrer shafts play an important role to
seal the openings of a bioreactor. As a result,
it restricts the entry of air from outside.
• One type of seal used in both small and large
scale fermenter is the mechanical seal.
• The seal is divided into two parts, first is the
stationary bearing housing and the second
rotates on the shaft. These two parts are
pressed together by springs.
• Steam condensate is used to lubricate and
cool the seals during operation and provides
protection against the contamination.

18. Sparger
• A sparger is a device that introduces air into the liquid
medium in a fermenter. There are three main types of
fermenter used in industrial-scale bioreactors such as
• Porous Sparger: It is made up of sintered glass, ceramics or
metals’ and are mostly used in laboratory-scale bioreactors.
As it introduces air inside a liquid medium, bubbles are
formed
• Orifice Sparger: These are used in small stirred fermenters
where perforated pipes are used and attached below the
impeller in the form of a ring. The air holes are mostly
drilled under the surface of the tubes.
• Nozzle Sparger: This is used in industrial-scale fermenters.
The main characteristic of this kind of sparger is that it
contains a single open or partially closed pipe as an air
outlet.

20. 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. Baffles are often attached to cooling coils
to increase the cooling capacity of the
fermenter.

22. Temperature control
• During the fermentation process heat can be produced
mainly in two ways, firstly microbial biochemical reactions
and secondly mechanical agitation.
• A temperature control helps to control the temperature at
the optimum level by removing or providing heat. The extra
heat is provided by hot bath or internal heat coil or heating
jacket with a water circulation system or silicon heating
jacket.
• The silicon heating jacket consists of silicon rubber mats
with heating wires and it is wrapped around the fermenter.
• In the case of pilot-scale fermenters, it is not possible to
use silicon jackets due to large size. In such cases, an
internal heating coil is used for providing extra heat while
cold water circulation helps to remove excess heat.

24. pH control
• All types of fermenters are attached with a
pH control sensor which consists of a pH
sensor and a port to maintain the pH inside of
the fermenter. pH alteration can lead to death
of the organism which leads to product loss.
Foam control device
• A Foam controlling device is placed on the
top of fermentor with a inlet into fermentor.
This device contains a small tank containing
anti-foaming agent.

25. Foam checking probe
pH checking probe

26. Cooling Jacket:
• The fermenter is fitted externally with a cooling
jacket through which steam (for sterilization)
or cooling water (for cooling) is run.
Use of Computer in Fermenter
• Computers are used to model fermentation
processes in industrial fermenters.
• Integration of computers into fermentation
systems is based on the computers capacity for
process monitoring, data acquisition, data
storage, and error-detection

28. TYPES OF FERMENTOR
Following are the types of fermenter
• Airlift Fermenter
• Continuous Stirred Tank Bioreactors
• Photo-Bioreactors
• Bubble Column Fermenter
• Fluidized Bed Bioreactors
• Packed Bed Bioreactors

29. AirliftFermenter
• The simple type
• Used for continuous culture
• In airlift fermenter the liquid culture volume of the vessel
is divided into two interconnected zones by means of a
baffle or draft tube.
• Draft tubes promote better mass transfer and mixing
• One of the two zones is sparged with air or other gas
• This sparged zone is known as the riser.
• The other zone that receives no gas is called down-comer.
• Mainly two types- internal loop and external loop

31. • Suited for aerobic culture and fermentation
• Production of beer, yeast and SCP
• Used for Waste water treatment
• For production of Proteins from cells

33. ContinuousStirredTankBioreactors
• Common model in chemical and
environmental engineering
• A continuous stirred tank bioreactor
consists of a cylindrical vessel with motor
driven central shaft that supports one or
more agitators (impellers).
• The mixing device promote efficient
mixing
• The shaft is fitted at the bottom of the
bioreactor.
• The number of impellers is variable and
depends on the size of the bioreactor i.e.,
height to diameter ratio, referred to as
aspectratio.

34. • Several types of impellers (Rustom disc,
concave bladed, marine propeller etc.) are
in use.
• The air is added to the culture medium under
pressure through a device called sparger.
• The sparger may be a ring with many holes or
a tube with a single orifice.
• The sparger along with impellers (agitators)
enables better gas distribution system throughout
the vessel.
• The bubbles generated by sparger are broken
down to smaller ones by impellers and
dispersed throughout the medium.
• This enables the creation of a uniform and
homogeneous environment throughout the
bioreactor.

35. • Suited also for anaerobic process
• Used for waste water treatment
– Biogas production
– Pharmaceutical products

37. Photo-Bioreactors:
• These are the bioreactors specialized for fermentation
that can be carried out either by exposing to sunlight
or artificial illumination.
• Mainly employed for the cultivation of photosynthetic
organisms
• Provide controlled supply of environmental
conditions
• Has two types – open system and closed system
• Open system are usually outdoor reactors/ open
pond reactors build in large area
• Closed system are indoor reactors with artificial
setup
•

39. • Certain important compounds are produced by
employing photo-bioreactors e.g., p-carotene,
asthaxanthin.
• Used for growing algae and cyanobacteria
– Bioplastic production
– Waste water remediation
– Nutraceutical and pharmaceutical product
production
– Biofuel production

40. Bubble Column Fermenter
• Generate and control gas-liquid chemical reactions
• Bubble column fermenter is usually cylindrical with an
aspect (height to diameter) ratio of 4-6.
• Gas is sparged at the base of the column
through perforated pipes,perforated plates,or
sintered glass or metal micro-porous spargers.
• O2 transfer,mixing and other performance factors
are influenced mainly by the gas flow rate and
the properties of the fluid.

42. • Used for chemical processes
– Production of alcohols and fuels
– Also used as algal bioreator

43. Bubble Column
Fermenter

44. • Fluidized bed bioreactor is comparable to bubble
column bioreactor except the top position is
expanded to reduce the velocity of the fluid.
• The design of the fluidized bioreactors
(expanded top and narrow reaction column) is
such that the solids are retained in the reactor
while the liquid flows out.
• These bioreactors are suitable for use to carry
out reactions involving fluid suspended
biocatalysts such as immobilized enzymes,
immobilized cells, and microbial flocks.
FluidizedBed
Bioreactors:

46. • For an efficient operation of fluidized beds, gas is
spared to create a suitable gas-liquid-solid fluid bed.
• It is also necessary to ensure that the suspended
solid particles are not too light or too dense (too light
ones may float whereas to dense ones may settle at
the bottom), and they are in a good suspended state.
• Recycling of the liquid is important to maintain
continuous contact between the reaction contents and
biocatalysts.
• This enable good efficiency of bioprocessing.

47. PackedBedBioreactors:
• A bed of solid particles, with
biocatalysts on or within the matrix
of solids, packed in a column constitutes a
packed bed bioreactor.
• The solids used may be porous or
non-porous gels, and they may be
compressible or rigid in nature.
• A nutrient broth flows continuously over
the immobilized biocatalyst.
• The products obtained in the packed bed
bioreactor are released into the fluid and
removed.
• While the flow of the fluid can be
upward or downward, down flow under
gravity is preferred.