STRAIN IMPROVEMENT
When an organism producing available products is identified, it becomes necessary
to increase the product yield from fermentation to minimize production cost. Product
yield can be increased by developing a suitable medium for fermentation, refining the
fermentation process, improving the productivity of the strain.
Generally major improvements arise through the last approach. The techniques
and approaches used to genetically modify the organism to increase the
production of desired product is called strain improvement. It involves 3
methods.
1. Mutant selection
2. Recombination
3. rDNA technology
The success of fermentation depends on the strain of microorganism which we use.
Hence an ideal strain should possess certain important characteristics
It should be pure and free from any contaminants.
It should be genetically stable but amenable to genetic modification.
It should be a high yielding strain.
It should have stable biochemical characteristics.
It should produce a desired product in increased concentration.
It shouldn't produce any undesirable products.
1. Mutant selection
Microorganisms are usually obtained from sources like soil, water and air and they
are isolated by screening techniques. The microorganisms isolated by screening
techniques are not sufficient as to be used in industrial fermentation; hence their
efficiency has to be improved to increase the concentration of the desired product.
Once organism has been isolated the product production can be increased by
mutation, recombination and rDNA technology. Natural isolate usually produce
commercially valuable products in very low concentration, hence attempts are made
, to increase the productivity of isolated organism. The productivity of an organism is
controlled by the genome and the genome must be modified to increase the potential
yield. Genetic modifications can be achieved by several approaches as below
Selection through natural variations
Selection through induced mutations
Selection through recombination
Selection through rDNA technology
Selection of natural variants
A microbial culture undergoes various divisions resulting in a heterogeneity which
presents serious problems of yield, degeneration etc. Therefore some variants are
inferior producers while some are superior producers.
Example in certain mycelia organisms actinomycetes the heterokaryosis produced
as a result of mutation are inferior produces while some uninucleated spores
resulted in homokaryosis are superior producers. Selection of natural variants in
some cases result in an increased yield but we cannot rely completely on such
improvements. Hence various techniques are employed to increase the yield of
culture which induces mutation and recombination. The most advanced technique of
strain improvement which result in organism producing compounds which are not
able to produce naturally are obtained through rDNA technology but the technology
of mutant isolation has contributed enormously for the development of various
industrial strains. Although rDNA technology is the most advanced technology it is
uneconomical.
Selection of induced mutants
Mutations are defect that occur during replication. It occurs in the genotype and in
most cases it is irreversible. Mutation is induced by mutagens followed by selection
of improved strains. Many mutations bring about marked changes in biochemical
characters
There are two types of mutations major and minor
Major mutation affects the pattern of metabolite production
When an organism producing available products is identified, it becomes necessary
to increase the product yield from fermentation to minimize production cost. Product
yield can be increased by developing a suitable medium for fermentation, refining the
fermentation process, improving the productivity of the strain.
Generally major improvements arise through the last approach. The techniques
and approaches used to genetically modify the organism to increase the
production of desired product is called strain improvement. It involves 3
methods.
1. Mutant selection
2. Recombination
3. rDNA technology
The success of fermentation depends on the strain of microorganism which we use.
Hence an ideal strain should possess certain important characteristics
It should be pure and free from any contaminants.
It should be genetically stable but amenable to genetic modification.
It should be a high yielding strain.
It should have stable biochemical characteristics.
It should produce a desired product in increased concentration.
It shouldn't produce any undesirable products.
1. Mutant selection
Microorganisms are usually obtained from sources like soil, water and air and they
are isolated by screening techniques. The microorganisms isolated by screening
techniques are not sufficient as to be used in industrial fermentation; hence their
efficiency has to be improved to increase the concentration of the desired product.
Once organism has been isolated the product production can be increased by
mutation, recombination and rDNA technology. Natural isolate usually produce
commercially valuable products in very low concentration, hence attempts are made
, to increase the productivity of isolated organism. The productivity of an organism is
controlled by the genome and the genome must be modified to increase the potential
yield. Genetic modifications can be achieved by several approaches as below
Selection through natural variations
Selection through induced mutations
Selection through recombination
Selection through rDNA technology
Selection of natural variants
A microbial culture undergoes various divisions resulting in a heterogeneity which
presents serious problems of yield, degeneration etc. Therefore some variants are
inferior producers while some are superior producers.
Example in certain mycelia organisms actinomycetes the heterokaryosis produced
as a result of mutation are inferior produces while some uninucleated spores
resulted in homokaryosis are superior producers. Selection of natural variants in
some cases result in an increased yield but we cannot rely completely on such
improvements. Hence various techniques are employed to increase the yield of
culture which induces mutation and recombination. The most advanced technique of
strain improvement which result in organism producing compounds which are not
able to produce naturally are obtained through rDNA technology but the technology
of mutant isolation has contributed enormously for the development of various
industrial strains. Although rDNA technology is the most advanced technology it is
uneconomical.
Selection of induced mutants
Mutations are defect that occur during replication. It occurs in the genotype and in
most cases it is irreversible. Mutation is induced by mutagens followed by selection
of improved strains. Many mutations bring about marked changes in biochemical
characters
There are two types of mutations major and minor
Major mutation affects the pattern of metabolite production
