MUTANT SELECTION PROGRAMME OF INDUSTRIAL MICROORGANISMS

 Dr.Jitender Kumar

Assistant Professor

Biotechnology Department���

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Mutant selection

• Crowded plate technique
• Feedback control in batch culture
• Continuous culture technique

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Regulation of biosynthesis

• Control of feed back mechanism
• Growth condition manupulation

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Biochemical pathways

• The Lysine Pathway in Corynebacterium glutamicum
• Threonine pathways

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Feed back control

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• No switch off occurs unless both lysine and�threonine build up
• Mutants selection will be done�

Isolation of mutants

• Lysine production using Corynebacterium glutamicum a mutant that cannot convert aspartate semi-aldehyde to homoserine
• Similar mutants for other amino acids

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Biochemical production

• Lysine production using Corynebacterium glutamicum medium must contain limited amount of homoserine
• Threonine levels will remain low, so no control�will be exercised when high levels of lysine�build up

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Types of mutants

• Finding Mutants which do not recognize Inhibitors.
• Repressors mutants which have lost an enzyme production system.
• Revertants mutants�

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Growth conditions

• Select strains which can grow in the presence of a compound very similar to a product or�intermediary (an analogue) which can produce a compound of interest.
• Production assays

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Enzyme regulation

• Different substrates
• Biochemical pathways
• Feedback control

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Catabolite repression

• Catabolite repression when readily utilized carbon sources are available to organisms catabolite repression may occur
• May override induction mechanisms
• Whole pathways my be switched off

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Regulation of production system

• Catabolite Repression
• Feedback control �

Inhibitors

• Avoiding Problems with Catabolite Repression use fed batch cultures
• Use mutants which lack catabolite repression i.e.can grow in high levels of glucose and still�express galactosidase�

Maintenance

• Ideal producing strains
• Testing under different conditions
• How to Maintain them so they do not mutate

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Preservations

• Culture collection centers
• Collection source material for R D.
• Strain preservation during screening and�optimisation.
• Starter cultures for production.

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References

• Pelczar, M.T. Microbiology, Tata McGraw Hill Publication, New Delhi.
• Stanier, R.Y. General microbiology, MacMillan Press, London.
• Prescott and Dunn. Industrial Microbiology 4^th Edition, CBS Publishers & Distributors.

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• Thank You