Fermentation is a form of metabolism where organic compounds are broken down without oxygen. Common fermentation products include ethanol, glycerol, lactic acid, acetone, and butanol. Fermenters are bioreactors used to carry out fermentation on an industrial scale, ranging in size from liters to hundreds of cubic meters. Important components of fermentation include the fermentation medium, which provides nutrients, and inoculum, cells introduced to initiate growth. Rates of substrate consumption and product formation are important for mass balances in fermenters. Catabolism generates energy for anabolism and maintenance through electron donor-acceptor couples.

1. Fermentation
Technology
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Shubham
Dubey
Tybsc
Microbiology

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3. What is fermentation?
• Pasteur’s definition: “life without
air”, anaerobe red ox reactions in
organisms
• New definition: a form of metabolism
in which the end products could be
further oxidized
For example: a yeast cell obtains 2
molecules of ATP per molecule of
glucose when it ferments it to ethanol
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Some important fermentation products
Product Organism Use
Ethanol Saccharomyces
cerevisiae
Industrial solvents,
beverages
Glycerol Saccharomyces
cerevisiae
Production of
explosives
Lactic acid Lactobacillus
bulgaricus
Food and
pharmaceutical
Acetone and
butanol
Clostridium
acetobutylicum
Solvents
-amylase Bacillus subtilis Starch hydrolysis

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Some
important
fermentation
products

6. Some important
fermentation products
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7. Fermenter
• The heart of the fermentation process is
the fermenter.
• In general:
• Stirred vessel, H/D  3
• Volume 1-1000 m3 (80 % filled)
• Biomass up to 100 kg dry weight/m3
• Product 10 mg/l –200 g/l
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8. Types of fermenter
• Simple fermenters (batch and continuous)
• Fed batch fermenter
• Air-lift or bubble fermenter
• Cyclone column fermenter
• Tower fermenter
• Other more advanced systems, etc
The size is few liters (laboratory use) - >500 m3 (industrial applications)
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9. Cross section
of a fermenter
for Penicillin
production
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10. Fermentation medium
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Define medium 
nutritional, hormonal,
and substratum
requirement of cells
In most cases, the
medium is independent
of the bioreactor
design and process
parameters
The type: complex and
synthetic medium
(mineral medium)
Even small
modifications in the
medium could change
cell line stability,
product quality, yield,
operational
parameters, and
downstream
processing.

11. Medium composition
• Fermentation medium consists of:
• Macronutrients (C, H, N, S, P, Mg
sources  water, sugars, lipid, amino
acids, salt minerals)
• Micronutrients (trace elements/
metals, vitamins)
• Additional factors: growth factors,
attachment proteins, transport proteins,
etc)
• For aerobic culture, oxygen is sparged
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12. Inoculums
• Incoculum is the substance/ cell culture
that is introduced to the medium. The cell
then grow in the medium, conducting
metabolisms.
• Inoculum is prepared for the inoculation
before the fermentation starts.
• It needs to be optimized for better
performance:
• Adaptation in the medium
• Mutation (DNA recombinant, radiation,
chemical addition)
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Microbial rates of consumption or production
C, N, P, S source
H2O
H+
O2
heat
product
CO2
biomass

14. What are the
value of rates?
Rates of
consumption or
production are
obtained from
mass balance
over reactors
• Mass balance over reactors
• Transport + conversion =
accumulation
• (in – out) + (production –
consumption) = accumulation
• Batch: transport in = transport
out = 0
• Chemostat: accumulation =
0, steady state
• Fed batch: transport out = 0
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15. Coupled anabolism/catabolism
• C-source (anabolism) and electron-donor (catabolism) are often the
same (e.g. organic substrate)
• Only a fraction of the substrate ends in biomass as C-source, while the
rest is catabolized as electron-donor to provide energy for anabolism and
maintenance
• YSX is the result of anabolic/catabolic coupling.
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Anabolism
Amino acids  protein
Sugars  carbohydrate
Fatty acids  lipids
Nucleotides  DNA, RNA
Sum of all reactions gives the anabolic reaction
(…)C-source + (…)N-source + (…) P-source + O-source
C1H1.8O0.5N0.2 + (…)H2O + (…)CO2
Thermodynamically, energy is needed. Also for cells
maintenance
energy

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Catabolism
• Catabolism generates the energy needed for
anabolism and maintenance. It consist of electron
donor couple and electron donor acceptor couple
• For example:
• Glucose + (…)O2  (…)HCO3
- + H2O
• donor couple: glucose/HCO3
-
• acceptor couple: O2/H2O
• Glucose  (…)HCO3
- + (…)ethanol
• donor couple: glucose/HCO3
-
• acceptor couple: CO2/ethanol
• The catabolism produces Gibbs energy
(Gcat.reaction)