This document provides information on different types of fermentation processes including aerobic fermentation, anaerobic fermentation, batch fermentation, fed-batch fermentation, semi-continuous fermentation, and continuous fermentation. It discusses the key differences between aerobic and anaerobic fermentation, and describes the typical phases of batch fermentation. Information is also given on characteristics and applications of fed-batch, semi-continuous, and continuous fermentation.

1. Aerobic fermentation
Anaerobic, Batch, Continuous
fermentation
By
Harinatha Reddy A
Department of Biotechnology
biohari14@gmail.com

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3.  The term “Aerobic fermentation” is misnamed because
fermentation is an anaerobic process.
 Simply, this is a process of burning simple sugars to energy in cells;
more scientifically, it can be called aerobic respiration.
 Yeast cell ferment glucose in the presence of oxygen and without
oxygen.

Aerobic Fermentation:

4.  The key difference between aerobic and anaerobic fermentation
is that aerobic fermentation uses oxygen whereas anaerobic
fermentation does not use oxygen.

5.  Aerobic” fermentation means that oxygen is present.
 Wine, beer and acetic acid, vinegar need oxygen in the “primary”
or first stage of fermentation.
 When creating vinegar, for example, exposing the surface of the
vinegar to as much oxygen as possible, creates a healthy, flavourful
vinegar with the correct pH.

6. Anaerobic fermentation:

7.  Fermentation is a metabolic process that consumes sugar in the
absence of oxygen.
 The products are organic acids, gases, alcohol, lactic acid.
 It occurs in yeast and bacteria, and also in oxygen-starved muscle
cells, as in the case of lactic acid fermentation.
 In 1857, Louis Pasteur concluded that alcoholic fermentation can be
caused by living yeast under anaerobic conditions.

8. 1. Ethanol fermentation
2. Lactic acid fermentation
3. Methane gas production in fermentation
 In methane gas production Acetic acid can undergo reduction by
Methanogenic bacteria and produce methane and carbon dioxide:
CH3COO− + H+ → CH4 + CO2
 The reduction of carbon dioxide into methane in the presence of
hydrogen can be expressed as follows:
CO2 + 4 H2 → CH4 + 2H2O

10. Batch Fermentation:

11. Batch Fermentation:
 A batch fermentation is regarded as a
closed system.
 The fermenter is first filled with the raw
material (carbon source).
 Then the microbes are added and
allowed to ferment of the raw material
under optimum pH and Temperature.


12.  The products remain in the fermenter until the completion of
fermentation.
 After fermentation, the products are extracted and the fermenter is
cleaned and sterilized before next round or batch.
 Thus here the fermentation is done as separate batches.

13.  Setup is not changed from outside once the fermentation is started.
 Nutrients are added only in the beginning and not added in between
the fermentation process.
 Environmental conditions in the fermenter will not be constant.

14.  Relatively larger size fermenters are used.
 Suitable for the production of secondary metabolites whose
production is not associated with the growth of the microbes.
Example: antibiotics
 Less investment required.
 Chance of contamination is less.

15. Under optimal conditions there are four typical phases of
growth was observed in batch fermentation:
 Lag phase
 Log phase or Exponential phase
 Stationary phase
 Death phase

16. Lag phase:
 No cell division and there is no net increase in mass, But cells
increase in size.
 The cells are synthesizing new components.
 Lag phase also know as Phase of cell enlargement or Preparation
phase/cell adjustment phase.

17. Log phase:
 Microorganisms are dividing at the maximal rate .
 Their growth rate is constant during the log phase.
 The population is most uniform in terms of chemical and
physical properties during this phase.
 Cells are small in size, and produce primary metabolites.

18.  In the stationary phase the total number of viable
microorganisms remains constant. This may result from a
balance between cell division and cell death.
 In this phase bacteria growth rate is decreases, Due to the,
deposition of toxic waste products and empty of nutrients.
 The secondary metabolites are produced in this phase.
Stationary Phase:

19. Death Phase:
 The number of viable cells are decline death phase.
 Environmental changes like nutrient deprivation and the buildup
of toxic wastes lead to the decline in the number of viable cells.

20. FED BATCH FERMENTATION:

21. fed batch fermentation:
• Fed-batch fermentation defined as an operational technique in
biotechnological processes where one or more nutrients
(substrates) are fed (supplied) to the bioreactor during cultivation
or fermentation.
• FBF is Semi-closed type………but not semi continuous.
• Periodical substrate addition prolongs log and stationary phases.

22.  It is difficult to measure substrate concentration in fed
batch fermentation.
 But production CO2, Tmp and Changes in pH may be measured.
 Addition of substrates (Carbon and nitrogen and trace metals)
increases the product yield.
 Fed-batch fermentation has become popular for the production of
alcohol and recombinant proteins.

23. Product inhibition:
 End products of fermentation such as methanol, ethanol, acetic
acid and lactic acid inhibit the growth of microorganisms.
 By adding such substrates or nutrients to fermenter properly log-
time can be increase the cell growth.

24. Characteristics Fed-batch culture
Cultivation system Semi-closed type
Addition of fresh nutrition Yes
Volume of culture Increases
Chance of contamination Maximum
Log phase longer
Product yield High

25. Semi Continuous fermentation:

26. Semi Continuous fermentation:
 In semi-continuous fermentation, a portion of the culture medium
is removed from the bioreactor and replaced by fresh medium
(identical in nutrients, pH and temperature etc.).

27.  In the semi-continuous fermentation, the lag phase and other
non-productive phases are very much shortened.
 The product output is much higher compared to batch culture
systems.
 Semi-continuous fermentation technique has been successfully
used in the industrial production of alcohol.

28.  These include the technical difficulties of handling bioreactors.
 Addition of nutrients that may cause contamination and
changes in physiological and metabolic characters of
microorganisms.
Disadvantages of semi-continuous fermentation.

29. Continuous culture or Continuous fermentation:

30. Continuous culture or Continuous fermentation:
 In Continuous fermentation the fresh medium is continuously
added and metabolic end products and microorganisms are
continuously removed at the same rate.
 It is an open system.
 Here the log phase of the microbes is maintained in the fermenter
for prolonged periods of time in by the addition of fresh media
are regular intervals.

31.  The continuous 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.

32.  Nutrients are added many times (in the beginning and in between
the fermentation process).
 The process is not stopped for the collection of the products, but
it is continuously taken out from the fermenter.

33.  Smaller size fermenter is required.
 The yield of the product is very high.
 Environmental conditions (pH, Tmp, con.CO2) in the fermenter will be
kept constant.
 Suitable for the primary metabolites whose production is associated
with the growth of the organism.
 Example: organic acids, amino acids.

34.  Less commonly used for large scale production.
 Chance of contamination is more.

35.  Two types of Continuous bioreactors:
1. Chemostat bioreactors
2. Turbidostat bioreactors

36. Chemostat bioreactors:
 A chemostat is a bioreactor to which fresh medium is continuously
added, and metabolic end products and microorganisms are
continuously removed.
 One of the most important features of chemostats is that
microorganisms can be grown in a physiological steady state
under constant environmental conditions and culture parameters.

37.  Chemostats are frequently used in the industrial manufacturing
of ethanol.
 Chemostats in research are used for investigations in cell
biology, as a source for large volumes of uniform cells or
protein.
 Chemostats can also be used to enrich specific types of
bacterial mutants in culture such as auxotrophs.

38. Turbidostat bioreactors:
 A turbidostat is a continuous fermentation device, similar to a
chemostat.
 In this case turbidity measurement is used to monitor the addition
of nutrients, removal of end products and biomass concentration.

40. Applications of continuous fermentation:
 Continuous fermentation process have been used for the
production of antibiotics, organic solvents, single cell protein,
ethanol and waste water treatments.

41. Advantages of continuous fermentation:
 The size of the bioreactor are smaller than compared to batch
fermentation.
 The yield of the product is constant.
 Continuous fermentation may run continuously for a period of
30 to 40 days.

42. Disadvantages:
 It is not used widely in industries.
 Maintenance of sterile conditions is difficult.
 Nutrient variations also alter the growth and physiology of the cells
and product yield.

43. Or Increase

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