FERMENTATION
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Microbiologists consider fermentation as any
process for the production of a product by
means of mass culture of micro-organisms
Biochemists consider fermentation as an
energy generating process in which organic
compounds act as both electron donors and
acceptors
Fermentation is any of a group of chemical
reactions induced by living or non-living
ferments
that
split
complex
organic
compounds into relatively simple substances
FERMENTATION
The process of deriving energy from the
oxidation of organic compounds, such as
carbohydrates,
using
an endogenous
electron acceptor, which is usually an organic
compound
End-products Obtained by Fermentation
• Microbial cells
• Microbial metabolites
• Recombinant products
FERMENTATION
STERILIZATION
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loss of productivity
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Outgrow
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contaminate the final product
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contaminant may degrade the desired
product
Contamination of a bacterial fermentation
with phage could result in the lysis of the
culture
STERILIZATION
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Sterilizing the medium to be employed
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Sterilizing the fermenter vessel
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Sterilizing all materials to be added to the
fermentation during the process
Maintaining aseptic conditions during the
fermentation
STERILIZATION
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MEDIUM STERILIZATION
filtration, radiation, ultrasonic treatment,
chemical treatment or heat
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STERILIZATION OF THE FERMENTER
heating jacket or coils with steam 15 psi
FACTORS INFLUENCING MICROBAL GROWTH
pH
Optimum pH for bacteria is 6.5-7.5, yeasts 4-5,
molds 4-7. The pH of the medium should be
maintained at optimum level for the micro-organism
being employed to ensure better product yield
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Temperature
Optimum temperature for most of the bacteria is
370C and the optimum temperature for most fungi is
250C
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Nutrients
Micro-organisms require optimum concentrations of
nutrients like nitrogen, vitamins, and minerals for
maximum growth rate. This will be different for each of
the different types
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FACTORS INFLUENCING MICROBAL GROWTH
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Minerals
Calcium, chlorine, magnesium, phosphorous,
potassium and sulfur are the essential
minerals for all media. Other minerals like
copper,
cobalt,
iron,
manganese,
molybdenum, and zinc
Growth Factors
Vitamins, amino acids, and fatty acids are
used as growth factors in the fermentation
FACTORS INFLUENCING MICROBAL GROWTH
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Chelating Agents
Chelating agents prevent formation of
insoluble metal precipitates. They form
complexes with the metal ions present in
the medium and can be utilized by the
microorganisms
EDTA (ethylene diamine tetraacetic acid) is
able to form six bonds with a metal ion.
Other chelating agents are citric acid and
pyrophosphates
FACTORS INFLUENCING MICROBAL GROWTH
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Carbon Sources
Product formation is directly dependent on the rate
at which the carbon source is metabolized; also the
main product of fermentation determines the type
of carbon source to be used.
Carbohydrates
These are the most commonly used carbon sources
in the fermentation process.
Starch – maize, cereals, and potatoes
It is widely used in alcohol fermentation.
Malt and beer - barley grains contain high
concentrations of different carbohydrates like
starch, sucrose, cellulose and other sugars
Sucrose - sugar cane and molasses
FACTORS INFLUENCING MICROBAL GROWTH
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Oils and Fats
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Hydrocarbons
They also have anti-foaming properties but are
generally used as additives rather than as the
sole carbon source. Examples are olive oil,
cotton seed oil, soya bean oil, linseed oil, and
lard (animal fat).
C12-C18 alkanes can be used as carbon
sources. They are cheap, and have more carbon
and energy content per weight than sugars.
They can be used in organic acids, amino acids,
antibiotics,
enzymes,
and
proteins
fermentation.
FACTORS INFLUENCING MICROBAL GROWTH
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Nitrogen Sources
Ammonia, ammonium salts, and urea are the most
commonly used nitrogen sources in the
fermentation process. Ammonia also serves the
purpose of pH control.
Other substances used as nitrogen sources are
corn-steep liquor, soya meal, peanut meal, cotton
seed meal, amino acids, and proteins.
FACTORS INFLUENCING MICROBAL GROWTH
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Buffers
Buffers are used to maintain the pH of the
medium as microbial growth is affected by the
pH changes. Optimum pH for most
microorganisms is 7.0. Commonly used
buffers are calcium carbonate, ammonia, and
sodium hydroxide
Antifoaming Agents
Commonly used antifoaming agents are
stearyl alcohol, cotton seed oil, linseed oil,
olive oil, castor oil, soy bean oil, cod liver oil,
silicones, and sulphonates