A bioreactor is a device that supports a biologically active environment. It is used for growing cells or fermenting chemicals produced by cells. Bioreactors come in various designs depending on their application and scale of production. They provide control over environmental factors like temperature, pH, and aeration to optimize cell growth and product formation. Common bioreactor types include stirred tank, bubble column, packed bed, fluidized bed, and membrane bioreactors. Each bioreactor design aims to efficiently culture cells while controlling critical process parameters.

1. Bioreactors
Submitted by: 21SGM04, M.Sc.
Microbiology
Submitted To: DR. K. KAVITHA,
Assistant Professor, PG and Research
Department of Microbiology,
Sadakathullah Appa College
(Autonomous), Tirunelveli (Affiliated
to Manonmaniam Sundaranar
University, Abishekapatti)

2. Definition
 A bioreactor is a type of fermentation vessel that is used
for the production of various chemicals and biological
reactions.
 It is a closed container with adequate arrangement for
aeration, agitation, temperature and pH control, and
drain or overflow vent to remove the waste biomass of
cultured microorganisms along with their products.

3.  A bioreactor should provide for the
following:
1. Agitation (for mixing of cells and
medium),
2. Aeration (aerobic fermentors); for O2
supply,
3. Regulation of factors like temperature,
pH, pressure, aeration, nutrient feeding,
and liquid leveled.
4. Sterilization and maintenance of sterility,
and
5. Withdrawal of cells/medium

4. Bioreactor design
 The design and mode of operation of a bioreactor are based on
the production of an organism, optimum conditions required
for desired product formation, product value, and its scale of
production.
 Improve productivity and provide higher quality products at
lower prices.

5.  The material used for the construction of a bioreactor must
have the following important properties:
o It should not be corrosive.
o It should not add any toxic substances to the fermentation
media.
o It should tolerate the steam sterilization process.
o It should be able to tolerate high pressure and resist pH
changes.
 Some bioreactors are designed for small scale fermenters and
some for large scale industrial applications from the microbial
cell (few mm3) to shake flask (100-1000 ml) to the laboratory-
scale fermenter (1 – 50 L) to pilot level (0.3 – 10 m3) to plant
scale (2 – 500 m3) for large volume).

6. Principle
 The bioreactor is the heart of any biochemical process as it
provides an environment for microorganisms to obtain
optimal growth and produce metabolites for the
biotransformation and bioconversion of substrates into
desirable products.
 The reactors can be engineered or manufactured based on
the growth requirements of the organisms used.
 They can be used for the production of various enzymes
and other bio-catalysis processes.

8. Parts of the bioreactor and
their function
 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 to
work under controlled conditions.
 Glass and stainless steels are two types of fermenter
vessels used.
 The glass vessel - small-scale industries - non-toxic and
corrosion-proof.
 Stainless steel vessel - large scale industries- resist
pressure and corrosion.

9.  Heating and Cooling Apparatus
 The fermentor 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 for sterilization of the
nutrient medium and removal of the heat generated
during fermentation in the fermentor.

10.  Aeration System
 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 fermentor.
 The stirring accomplishes two things:
o It helps to mix the gas bubbles through the liquid
culture medium and
o It helps to mix the microbial cells through the liquid
culture medium which ensures the uniform access of
microbial cells to the nutrients.

11.  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:
o Packed gland seal
o Mechanical seal
o Magnetic drives
 Baffles
 The baffles are incorporated into fermenters to prevent a
vortex improve aeration in the fermenters.
 It consists of metal strips attached radially to the wall.

12.  Impeller: Impellers are used to provide uniform
suspension of microbial cells in different nutrient mediums.
 They are made up of impeller blades attached to a motor
on the lid.
 Impeller blades play an important role in reducing the
size of air bubbles and distribute them uniformly into the
fermentation media.
 Variable impellers are used in the fermenters and are
classified as follows.
o Disc turbines
o Variable pitch open turbine

13.  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
o Porous sparger
o Nozzle sparger
o Combined sparger–agitator

14.  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.
 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.

15.  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.
 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.

16. Types
 Continuous stirred tank bioreactor
 Bubble column bioreactor
 Packed bed reactors
 Fluidized bed bioreactors
 Photobioreactor
 Membrane bioreactor
 Rotary drum bioreactor
 Immobilized cell bioreactor
 Activated sludge bioreactor

17. Stirred tank bioreactors
 Stirred tank bioreactors, also known as
stirred tank fermenters, are bioreactors that
are designed to hold and mix a liquid culture
of microorganisms or cells. They typically
consist of a cylindrical tank with a stirrer or
impeller to mix the contents and provide
oxygen for respiration. Some key features of
stirred tank bioreactors include:
 Agitation
 Temperature control
 pH control
 Aeration
 Sterilization
 Monitoring and control
 Scalability

18.  Advantages of Stirred Tank Bioreactors
 Continuous operation.
 Excellent temperature control.
 It is easy to adapt easily to easily adapt to.
 The simplicity of construction Flexible and low operating (labor)
costs and investment requirements.
 Disadvantages of Stirred Tank Bioreactors
 The requirement for bearings and shaft seals.
 Limitation of size by motor size as well as shaft length and weight.
 The problem of foaming can be a major one.
 Power consumption is increased because of the Mechanical pressure
pumps.

19. Bubble column bioreactor
 The ratio for height-to-diameter is
usually between 4-6.
 Gas is sucked at the bottom by
perforated pipes or plates , or metal
spargers with porous materials.
 O2 transfer, mixing , and other
performance parameters are affected
mostly by the gas flow rate as well as
the characteristics of the gas.
 Mixing and mass transfer could be
improved by putting perforated plates,
or baffles with vertical sides within the
vessel.

20.  Advantages of Bubble column bioreactors
 High volumetric efficiency and outstanding heat
management.
 Greater utilization of the plate’s area as well as flow
distrubution.
 Self-regulating.
 Disadvantages of Bubble column bioreactors
 Inefficient compared to other bioreactors.
 Doesn’t have draft tube
 A higher consumption of catalysts that the bed fixed
 Installation costs are higher, and the design is difficult to
create

21. Packed bed reactors
 A bed of particles are confined in the
reactor. The biocatalyst (or cell) is
immobilized on the solids which may
be rigid or macroporous particles.
 A fluid containing nutrients flows
through the bed to provide the needs
of the immobilized biocatalyst.
Metabolites and products are released
into the fluid and removed in the
outflow.
 The flow can be upward or
downward.

22.  Advantages of Packed Bed Reactors
 Higher conversion per unit mass of catalyst than other catalytic
reactors
 Low operating cost.
 Continuous operation.
 No moving parts to wear out.
 Catalyst stays in the reactor. Reaction mixture/catalyst separation is
easy
 Design is simple
 Effective at high temperatures and pressures
 Disadvantages of Packed Bed Reactors
 Undesired heat gradients.
 Poor temperature control.
 Difficult to clean.
 Difficult to replace catalyst.
 Undesirable side reactions.

23. Fluidized bed bioreactors
 Suitable for reactions involving a fluid-suspended particulate
biocatalyst such as immobilized enzyme and cell particles.
 The properties include:
o Extremely high surface area contact between fluid and solid per
unit bed volume
o High relative velocities between the fluid and the dispersed
solid phase.
o High levels of intermixing of the particulate phase.
o Frequent particle-particle and particle-wall collisions.

24.  Advantages of Fluidized Bed
Bioreactor
 Uniform Particle Mixing
 Uniform Temperature Gradients
 Ability to Operate Reactor in
Continuous State
 Disadvantages of Fluidized Bed
Bioreactor
 Increased Reactor Vessel Size
 Lack of Current Understanding
 Erosion of Internal Components
 Pressure Loss Scenarios

25. Photobioreactor
 Photobioreactors are utilised for the photosynthetic
cultivation of microalgae and cyanobacteria to produce
astaxanthin and β-carotene, among other products.
Photosynthetic cultures require either natural or artificial
light.
 However, excessive light induces photoinhibition; in this
case, a little reduction in light intensity will increase the
rate of photosynthesis. As cell population increases, the
self-shading effect of cells further restricts light
penetration.

26.  Advantages of Photobioreactor
 Higher productivity
 Large surface-to-volume ratio
 Better control of gas transfer.
 Reduction in evaporation of growth
medium.
 More uniform temperature.
 Disadvantages of Photobioreactor
 Capital cost is very high.
 The productivity and production cost
in some enclosed photobioreactor
systems are not much better than
those achievable in open-pond
cultures.
 The technical difficulty in sterilizing

27. Membrane bioreactor
 Membrane bioreactors (MBR) are been used since 90s. It
basically combines traditional treatment system with filtration via
membranes resulting in removal of organic and suspended solid
matters that also removes high level of nutrients.
 Membranes in the MBR system are submerged in an aerated
biological reactor. The pore size of the membrane ranges from
0.035 microns to 0.4 microns.
 However, membrane fouling is a chief obstacle to the extensive
application of MBRs. Moreover large-scale use of MBRs in waste
water treatment will involve a notable worthy decrease in price of
the membranes

28.  Advantages
 The loss of
enzyme is
reduced.
 Enzyme lost by
denaturation can
be made up by
periodic addition
of enzyme.
 Substrate and
enzyme can be
easily replaced.

29. Rotary drum bioreactor
 The rotating-drum bioreactors comprise a horizontally
rotating drum, that may or may not have a paddle mixer and
rotates slowly for proper mixing of fermentation substrate.
For scaling-up purposes, many assumptions need to be made
concerning the rotating-drum bioreactors.
 The bioreactor is cylindrical (with a length L and
diameter D) and partially filed;

30.  Advantages of
Rotary Drum
Reactor
 High oxygen
transfer.
 Good mixing
facilitates better
growth
 Disadvantages of
Rotary Drum
Reactor: Difficult
to scale up.

31. Immobilized cell bioreactor
 The immobilized cell reaction (ICR) operates in accordance with
the principle of immobilization. The process of limiting the cell’s
mobility within a certain space.
 The interaction between hydrogen and hydrophobic and the
formation of salt bridges between the adsorbent as well as the cells
are the driving factors for immobilization.
 In general, immobilization can be divided into two kinds which are
passive and active.
o In the passive model cells, they are stuck naturally in the
matrix of solids, leading to the creation of biofilm.
o In active techniques Immobilization can be induced by a
physical or chemical method. This can occur in a variety of
ways like attachment, entrapment gathering, and confinement.

32.  Advantages: The harvesting of the product you want is a breeze
and requires any effort if the substances are released in the
medium
 Disadvantages There are some restrictions in the ICR like;
 A limitation in mass transfer due to the intraparticle diffusion
resistance, which restricts the ability of the substrate to get to
cells. This type of problem occurs in aerobic reactions, where
there is an oxygen shortage to cells, resulting in lower reactor
performance.
 Another issue is inhibition of the product in which the
concentration of the product is reduced within the inner core
and, consequently, the rate of reaction is also decreased.

33. Activated sludge bioreactor
 When an active sludge bioreactor is used the proportion of
microbes as well as the amount of oxygen and substrate are all the
same as the reactor is equipped with a homogeneous tank in which
the feed is dispersed throughout the. In the active sludge with plug
flow, the reactor has an extended channeled inlet which restricts any
growth in microorganisms as well as improves the ability of sludge
to settle.
 In the process of activated Sludge, sewage with organic matter is
pumped to the tank for aeration that is then metabolized because it
is filled with microorganisms. The organic matter that is
metabolized is converted to CO2 and water in order to generate
energy. A portion of the cells that have formed during the process
are eliminated from the process in sludge. The remaining sludge
returns to an aeration tank in which this process is carried on.

34.  Application
 The reactor is employed in the
treatment of wastewater and
sewage.
 This particular reactor is used
to produce biofuels such as
biogas, bioethanol and so on.
such as biofuels that are made
by milk-based waste.
 Advantage: The reactor can
be operated with high organic
loading rates.
 Limitation: This reactor is a
major consumer of energy and
also capital, The operating
expenses are high.