Fermentation is a process where microbes such as bacteria and fungi convert carbohydrates into products like alcohols, organic acids, or gases. It is an ancient technique used in foods and beverages. Modern industrial fermentation uses controlled bioreactors and genetically engineered microbes to efficiently produce metabolites. There are three main types of industrial fermentation processes - batch, continuous, and fed-batch - which differ in how nutrients are added and removed from the fermentation vessel over time to influence microbial growth phases and maximize metabolite production.

1. Sadia Rafique
M.Sc. Microbiology 3rd Semester
Industrial Microbiology

2. Fermentation is a metabolic process which converts
carbohydrates to
• alcohols
• Organic acids or
• Gases
By the activity of enzymes of microbial origin.
Microbes involved in fermentation process are
• Bacteria
• fungi
The process of anaerobic respiration in the muscle cells of
animals during exercise which produce Lactic Acid is also a
type of fermentation.

3. The technique of fermentation was very ancient
in origin.
Egyptians and Sumerians had the knowledge of
the technnique of converting “starchy grains to
alcoholics”

4. For a Microbiologist, the Fermentation means
many processes such as:
1. Method of mass cultivation of microbes under
aerobic and anaerobic conditions.
2. Spoilage of food by microbial activity.
3. Production of Alcoholic beverages, organic
acids, antibiotics and biopolymers
4. Partial oxidation of carbohydrates.

5. The intentional use of fermentation technology
for the large scale production of microbial
biomass or metabolites is called industrial
fermentation.
Fermented foods have immense use in food,
medicine and other industries.
Modern industrial fermentation units use
genetically engineered microbes for the rapid
production of desired metabolites

6. Fermentation is carried out in vessels known as Fermentors.
The types of fermentor ranges from simple tank to complex
integrated system of automated control.
The heart of industrial fermentation is a “fermenter”
Fermenter is a type of Bioreactor.
A Fermenter is a system provided with controlled
environmental conditions for the growth of microbes in liquid
culture and production of specific metabolites.
It is a device in which microbes are cultivated and motivated to
form the desired products.

7. It is a containment system to provide the accurate
environment for the optimum growth and
metabolic activity of the microbes (prokaryotic
cells e.g. Bacteria and eukaryote cells e.g. Fungi).
Fermenter prevents the growth of contaminating
microbes from outside.
A bioreactor is a containment system for the
cultivation of mammalian or insect cells.

9. A fermenter possesses the following mechanical
parts:
1. Large vessel made of stainless steel or rust free
material.
2. Motors provided with an automatic control
system.
3. Heaters with thermostat system for providing
and manipulating temperature.
4. Pumps for the addition or removal of substances
and water to the fermenters

10. 5. Gas source and pipeline system for aeration.
6. Sensors for pH and aeration.
7. Peripheral manual or automatic controlling
facilities.
MAIN PARTS OF A FERMENTER & THEIR
USES

11. 1. A space for taking raw material (culture media/
carbon source)
2. Provide a contamination free environment for the
growth of microbes.
3. Maintain optimum temperature in the system.
4. Provide adequate mixing and agitation in the system.
5. Provide ample aeration for aerobic fermentation.

12. 6. Control and maintain optimum pH condition in the fermenter.
7. Monitor the conc. Of dissolved oxygen in the system
8. Allows addition of nutrients in between the fermentation
process
9. Facility for maintaining a wide range of organisms.
10. Provision for collecting overflow from the fermenter (in
continuous fermentation)
MECHANICAL COMPONENTS OF
THE FERMENTER

13. There are 3 types of industrial fermentation
processes based on the methods of fermentation
and types of fermenters.
1) Batch fermentation
2) Continuous fermentation
3) Fed-batch fermentation

14. • Microorganism is inoculated into a fixed volume of
medium
• As the growth takes place, the nutrients are consumed
and the product of growth accumulates in the fermenter.
• Product of growth may be of 2 types:
(a) Biomass
(b) Metabolites
• The nutrient environment in the fermenter is
continuously changed.

15. • This change in the environment in the fermenter will
enforce change in the metabolism of cells.
• This result in the cessation of cell multiplication.
• Cessation of growth is due to the scarcity of nutrients
and accumulation of metabolites.
• Once the microbes reached the stationary phase they
start to accumulate the metabolites.

16. • Metabolites are extracted from the fermenter by
Downstream process.
• After the fermentation is over, the residues are
taken out from the fermentation tank, and the
vessel is then cleaned and sterilized before next
batch of fermentation.
• Thus in Batch fermentation, the large scale
production is done as separate batches.

17. • Microbes in the batch culture show the following pattern of growth with
distinct phases.

18. 1. Lag Phase
Growth is a result of consumption of nutrients. The
initial lag phase is a time of no apparent growth but
actual biochemical analyses show metabolic
turnover, indicating that cells are in the process of
adapting to the environmental conditions and that
new growth will eventually begin.
2. Transient acceleration
There is then a transient acceleration phase as the
inoculum begins to grow, which is quickly followed
by an exponential phase.

19. 3. Exponential Phase
In the exponential phase, microbial growth proceeds
at the maximum possible rate for that organism with
nutrients in excess, ideal environmental parameters
and growth inhibitors absent.
4. Deceleration phase
However, in batch cultivations exponential growth is
of limited duration and as nutrient conditions
change, growth rate decreases, entering the
deceleration phase.

20. 5. Stationary Phase
Deceleration phase, to be followed by the
stationary phase, when overall growth can no
longer be obtained owing to nutrient exhaustion.
6. Death Phase
The final phase of the cycle is the death phase
when growth rate has ceased. Most
biotechnological batch processes are stopped
before this stage because of decreasing metabolism
and cell lysis. Typical microbial cultures in the
laboratory (in a flask) are batch cultures.

21. • Here the exponential growth rate the microbes is
maintained in the fermenter for prolonged periods of
time in by the addition of fresh media are regular
intervals.
• Microbes reach the exponential growth rate and
continue as such due to the availability of nutrients.
• The exponential growth rate of microbes continuous
till the vessel becomes completely filled in the cells.

22. • Continuous fermenter possesses devices for the
collection of overflow by downstream processing.
• Thus unlike batch fermentation, in continuous
fermentation, the fermentation process never stops in
between and it continues to run for a long period of time
with the addition of nutrients and harvesting the
metabolites at regular intervals.

23. • It is a modified version of batch fermentation.
• Here the substrate is added in increments at different
times throughout the course of fermentation.
• Periodical addition of substrate keeps the prolonged
log and stationary phase of the microbes in the
fermenter.

24. • This result in the rapid increase of biomass.
• Consequently increased production of metabolites can
be achieved in the stationary phase.
• Thus fed-batch technique is an improved version of
fermentation by avoiding the disadvantages of batch
and continuous fermentation techniques.