Microbiology of Metabolite Production

 Dr.Jitender Kumar

Assistant Professor

Biotechnology Department���

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Metabolites and their production

• Different metabolites production system were analyzed
• Study of populations for constitutive mutants by Chemostat cultures where the enzyme substrate is the limiting nutrient (e.g. lactose)

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Production System

• Continuous culture system
• The Chemostat
• Turbidostat

Batch Culture

• Enrich populations for constitutive mutants by Sequential batch cultures alternating use of the�inducing substrate as a nutrient with use of an�alternate nutrient.
• Example sequential cultures of Escherichia coli�alternating lactose and glucose will enrich for�mutants constitutive for beta galactosidase.

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Types of Mutants

• Finding Constitutive Mutants
• Revertants mutants
• Analogous revertants mutants

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Regulation

• Inhibition/Repression Build up of enzyme product (or another intermediate or end product further down the metabolic pathway)
• Inhibit the enzyme activity.

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Enzyme regulation

• Switches off enzyme production (repression).
• Avoid build-up of inhibitor/repressor.
• Find mutants lacking inhibition/repression�control.

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Effector Molecules

• Avoiding Build-up of Inhibitors and Repressor
• Modifying biochemical pathways.
• Simple pathway example lysine production by�Aerobacter aerogenes.
• Branched pathway example lysine production by�Corynebacteium glutamicum and effect of�progressive and concretive inhibition.

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Biochemical Pathways

• Simple Pathway the lysine pathway in Aerobacter aerogenes in normal cells, feedback control stops the build up of lysine by acting at an early stage in the�pathway.
• Role of inducers in pathways

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Metabolite Productivity

• Lysine Production using Aerobacter aerogenes a dual fermentation is used
• Cultures of two different strains (A & B) are�grown up separately and then added together in the presence of acetone which breaks down�permeability barriers and allows the cell�contents to mix.

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Substrate level Inhibition

• Selection of strain for utilization of substrates
• Grow in medium with plenty of glycerol and�limiting amounts of lysine
• Large amounts of growth factors

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Selection of Strains

• Select an appropriate mutant
• The normal wild type strain.
• Growth does not produce build up of lysine or�intermediates.
• Biochemical pathways for lysine

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Production level

• What happens when the cultures are mixed the mixture contains large amounts of L,L and Meso DAP (from strain A).
• The enzymes necessary for their conversion to�lysine.
• The resultant is the production of large�quantities of lysine.

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Control Mechanism

• Feedback control in branched pathways�Progressive and Concerted Control Product levels at the end of branches control the�pathway at a point before branching occurs.
• End product accumulation

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Feedback control

• Feedback control is most fundamental pathway for production of biochemical
• Control is progressive build up of one end�product causes partial switch off further�switch off occurs if there is build up at the end�of another branch and so on.

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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, By S.K. Jain for CBS Publishers & Distributors.
• Tortora. G.J., Funke. B.R., Microbiology: An Introduction, Benjamin Cummings.

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Thank You