Types of fermentation process:
• There are five major groups of commercially important fermentations>
1. Those that produce microbial cells or biomass as the product
2. Those that produce microbial enzymes
3. Those that produce microbial metabolites
4. Those that produce recombinant products
5. Those that modify a compound which is added to the fermentation- the
transformation process.
1. Microbial biomass:
• The commercial production of microbial biomass may be divided into two major processes.
a. The production of yeast to be used in the baking industry
b. The production of microbial cells to be used in human or animal food (single cell protein)
2. Microbial enzymes:
• Enzymes have been produced commercially from plant, animal and microbial sources.
• However microbial enzymes have the enormous advantage of being able to be produced in
large quantities by established fermentation techniques, also it is easier to improve the
productivity of a microbial system compared with plant or animal one.’
• Furthermore, the advent of recombinant DNA technology has enabled enzymes of animal
origin to be synthesized by microorganisms.
• Enzyme production is closely controlled in microorganisms and in order to improve
productivity these controls may have to be exploited or modified. Also , the number of gene
copies coding for he enzyme may be increased by recombinant DNA techniques.
3. Microbial metabolites:
• The growth of a microbial culture can be divided into a number of stages
• After the inoculation of a culture into a nutrient medium there is a period during
which growth does not appear to occur; this period is referred to as the lag phase
and may be considered as a time of adaptation.
• Following a period during which the growth rate of the cells gradually increases the
cells grow t a constant, maximum rate and this period is known as the log, or
exponential phase.
• Eventually the growth ceases and the cells enter the so-called stationary phase
• After a further period of time the viable cell number declines as the culture enters
the death phase.
• As well as this kinetic disruption of growth, the behavior of a culture may also be
described according to the products which it produces during the various stages of
the growth curve.
• During the log phase of growth the products produced are essential to the growth
of the cells and include amino acids, nucleotides, proteins, nucleic acids, lipids,
carbohydrates etc.
• These products are referred to as the primary products of metabolism and the
phase in which they are produced as the tropophase.
• Many products of primary metabolism are of considerable economic importance
and are being produced by fermentation.
• The synthesis of primary metabolites by wild type microorganism is such that their
production is sufficient to meet the requirement of the organism.
, • During the deceleration and stationary phases some microbial cultures synthesize
compounds which are not produced during the tropophase and which do not
appear to have any obvious function in cell metabolism.
• These compounds are referred to as the secondary compound of metabolism and
the phase in which they are produced as the idiophase.
• It is important to realize that secondary metabolism may occur in continuous
cultures at low growth rates and is a property of slow-growing , as well as
nongrowing cells.
• Microorganism grow at relatively low growth rates in their natural environments, it
is tempting to suggest that it is the idiophase state that prevails in nature rather
than tropophase, which may be more of a property of microorganisms in culture.
• Many secondary metabolites have antimicrobial activity, others are specific enzyme
inhibitors, some are growth promoters and many have pharmacological properties.
• Thus the products of secondary metabolism have formed on the basis of a number
of fermentation processes
• As is the case for primary metabolites, wild type microorganisms tend to produce
only low concentration of secondary metabolites, their synthesis being controlled
by induction, catabolite repression and feed back systems.
4. Recombinant products:
• The advent of recombinant DNA technology has extended the range of potential
fermentation products.
• Genes of higher organism may be introduced into microbial cells such that recipients
are capable of synthesizing foreign proteins.
• A wide range of microbial cells have been used as hosts for such systems including
Escherichia coli, Saccharomyces cerevisiae and filamentous fungi
• Products produced by such genetically engineered organisms include interferone,
insulin, human serum albumin, factor VIII and IX, epidermal growth factor.
• Important factors in the design of these processes include the secretion of the
product, minimizing the degradation of the product and control of the onset of
synthesis during the fermentation as well as maximizing the expression of the
foreign gene.
5. Transformation processes:
• Microbial cells may be used to convert a compound into a structurally related,
financially more valuable compound
• Microbial processes are more specific than purely chemical ones and enable the
addition , removal or modification of functional groups at specific sites on a complex
molecule without the use of chemical protection.
• The reaction which may be catalyzed include dehydrogenation, oxidation,
hydroxylation, dehydration and condensation, decarboxylation, amination,
deamination and isomerization.
• Microbial processes have the additional advantage over chemical reagents of
operating at relatively low temperatures and pressures without the requirement for
potentially polluting heavy metal catalysts.
• The majority of these processes involve the production of high value compounds
including steroids, antibiotics and prostaglandins.
,• The anomaly of the transformation fermentation process is that a large biomass has
to be produced to catalyze a single reaction.
• Thus many processes have been streamlined by immobilizing either the whole cells,
or the isolated enzymes which catalyzes the reaction on an inert support. The
immobilized cells or enzymes may then be considered as catalysts which may be
reused many times.
, Isolation of industrially important
microorganisms:
The first stage in the screening for microorganisms of potential industrial application
is their isolation.
Isolation involves obtaining either pure or mixed cultures followed by their
assessment to determine which carry out the desired reaction or produce the
desired product.
The selection of the culture to be used is a compromise between the productivity of
the organism and the economic constraints of the process.
There are a number of criteria important in the choice of organism.
1. The nutritional characteristics of the organism. It is frequently required that a
process be carried out using a very cheap medium or a predetermined one. (Ex.
Use of methanol as energy source.) These requirements may be met by the
suitable design of the isolation medium.
2. The optimum temperature of the organism. The use of an organism having an
optimum temperature above 40⁰C considerably reduces the cooling costs of a
large scale fermentation and therefore, the use of such a temperature in the
isolation procedure may be beneficial.
3. The reaction of the organism with the equipment to be employed and the
suitability of the organism to the type of process to be used.
4. The stability of the organism and its amenability to genetic manipulation
5. The productivity of the organism, measured in its ability to convert substrate into
product and to give a high yield of product per unit time.
6. The ease of product recovery from the culture.
• There are five major groups of commercially important fermentations>
1. Those that produce microbial cells or biomass as the product
2. Those that produce microbial enzymes
3. Those that produce microbial metabolites
4. Those that produce recombinant products
5. Those that modify a compound which is added to the fermentation- the
transformation process.
1. Microbial biomass:
• The commercial production of microbial biomass may be divided into two major processes.
a. The production of yeast to be used in the baking industry
b. The production of microbial cells to be used in human or animal food (single cell protein)
2. Microbial enzymes:
• Enzymes have been produced commercially from plant, animal and microbial sources.
• However microbial enzymes have the enormous advantage of being able to be produced in
large quantities by established fermentation techniques, also it is easier to improve the
productivity of a microbial system compared with plant or animal one.’
• Furthermore, the advent of recombinant DNA technology has enabled enzymes of animal
origin to be synthesized by microorganisms.
• Enzyme production is closely controlled in microorganisms and in order to improve
productivity these controls may have to be exploited or modified. Also , the number of gene
copies coding for he enzyme may be increased by recombinant DNA techniques.
3. Microbial metabolites:
• The growth of a microbial culture can be divided into a number of stages
• After the inoculation of a culture into a nutrient medium there is a period during
which growth does not appear to occur; this period is referred to as the lag phase
and may be considered as a time of adaptation.
• Following a period during which the growth rate of the cells gradually increases the
cells grow t a constant, maximum rate and this period is known as the log, or
exponential phase.
• Eventually the growth ceases and the cells enter the so-called stationary phase
• After a further period of time the viable cell number declines as the culture enters
the death phase.
• As well as this kinetic disruption of growth, the behavior of a culture may also be
described according to the products which it produces during the various stages of
the growth curve.
• During the log phase of growth the products produced are essential to the growth
of the cells and include amino acids, nucleotides, proteins, nucleic acids, lipids,
carbohydrates etc.
• These products are referred to as the primary products of metabolism and the
phase in which they are produced as the tropophase.
• Many products of primary metabolism are of considerable economic importance
and are being produced by fermentation.
• The synthesis of primary metabolites by wild type microorganism is such that their
production is sufficient to meet the requirement of the organism.
, • During the deceleration and stationary phases some microbial cultures synthesize
compounds which are not produced during the tropophase and which do not
appear to have any obvious function in cell metabolism.
• These compounds are referred to as the secondary compound of metabolism and
the phase in which they are produced as the idiophase.
• It is important to realize that secondary metabolism may occur in continuous
cultures at low growth rates and is a property of slow-growing , as well as
nongrowing cells.
• Microorganism grow at relatively low growth rates in their natural environments, it
is tempting to suggest that it is the idiophase state that prevails in nature rather
than tropophase, which may be more of a property of microorganisms in culture.
• Many secondary metabolites have antimicrobial activity, others are specific enzyme
inhibitors, some are growth promoters and many have pharmacological properties.
• Thus the products of secondary metabolism have formed on the basis of a number
of fermentation processes
• As is the case for primary metabolites, wild type microorganisms tend to produce
only low concentration of secondary metabolites, their synthesis being controlled
by induction, catabolite repression and feed back systems.
4. Recombinant products:
• The advent of recombinant DNA technology has extended the range of potential
fermentation products.
• Genes of higher organism may be introduced into microbial cells such that recipients
are capable of synthesizing foreign proteins.
• A wide range of microbial cells have been used as hosts for such systems including
Escherichia coli, Saccharomyces cerevisiae and filamentous fungi
• Products produced by such genetically engineered organisms include interferone,
insulin, human serum albumin, factor VIII and IX, epidermal growth factor.
• Important factors in the design of these processes include the secretion of the
product, minimizing the degradation of the product and control of the onset of
synthesis during the fermentation as well as maximizing the expression of the
foreign gene.
5. Transformation processes:
• Microbial cells may be used to convert a compound into a structurally related,
financially more valuable compound
• Microbial processes are more specific than purely chemical ones and enable the
addition , removal or modification of functional groups at specific sites on a complex
molecule without the use of chemical protection.
• The reaction which may be catalyzed include dehydrogenation, oxidation,
hydroxylation, dehydration and condensation, decarboxylation, amination,
deamination and isomerization.
• Microbial processes have the additional advantage over chemical reagents of
operating at relatively low temperatures and pressures without the requirement for
potentially polluting heavy metal catalysts.
• The majority of these processes involve the production of high value compounds
including steroids, antibiotics and prostaglandins.
,• The anomaly of the transformation fermentation process is that a large biomass has
to be produced to catalyze a single reaction.
• Thus many processes have been streamlined by immobilizing either the whole cells,
or the isolated enzymes which catalyzes the reaction on an inert support. The
immobilized cells or enzymes may then be considered as catalysts which may be
reused many times.
, Isolation of industrially important
microorganisms:
The first stage in the screening for microorganisms of potential industrial application
is their isolation.
Isolation involves obtaining either pure or mixed cultures followed by their
assessment to determine which carry out the desired reaction or produce the
desired product.
The selection of the culture to be used is a compromise between the productivity of
the organism and the economic constraints of the process.
There are a number of criteria important in the choice of organism.
1. The nutritional characteristics of the organism. It is frequently required that a
process be carried out using a very cheap medium or a predetermined one. (Ex.
Use of methanol as energy source.) These requirements may be met by the
suitable design of the isolation medium.
2. The optimum temperature of the organism. The use of an organism having an
optimum temperature above 40⁰C considerably reduces the cooling costs of a
large scale fermentation and therefore, the use of such a temperature in the
isolation procedure may be beneficial.
3. The reaction of the organism with the equipment to be employed and the
suitability of the organism to the type of process to be used.
4. The stability of the organism and its amenability to genetic manipulation
5. The productivity of the organism, measured in its ability to convert substrate into
product and to give a high yield of product per unit time.
6. The ease of product recovery from the culture.
