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Chapter 7

Chapter 7. Media for Industrial Fermentation. Steps to Medium Development. Design – nutritional requirements for growth and product formation Formulation – mass composition of cells, stoichiometry of growth and product formation Optimization . Media must meet the following criteria.

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Chapter 7

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  1. Chapter 7 Media for Industrial Fermentation

  2. Steps to Medium Development • Design – nutritional requirements for growth and product formation • Formulation – mass composition of cells, stoichiometry of growth and product formation • Optimization

  3. Media must meet the following criteria • It will produce a maximum yield of product at biomass per gram of substrate used. • It will produce a maximum concentration of product or biomass. • It will permit the maximum rate of product formation. • It will be the minimum yield of undesired product. • It will be cheap and of a consistent quality and is readily available throughout the year. • It will cause minimal problem in other aspects of production and agitation, extraction, purification and waste treatment.

  4. Macroelements • Constitutes 90-95% of the dry weight of microbial biomass • C, N, O, S, P, K, Mg • Microorganisms are heterotroph (obtain the cell carbon from organic compound) and autotrophs (obtain cell carbon from CO2) • Assimilated to provide cell carbon and energy – to synthesize cell material, osmotic work, cell motility • Eg Penicillin production: of the total amount of glucose consumed, 10% for carbon in biomass, 10% for energy for biomass synthesis, 10% penicillin carbon and energy, 70% for maintenance energy

  5. Macroelements [cont] • Range of C compounds: carbohydrates, alcohols, organic acids, hydrocarbons, organic nitrogen compounds • N requirements: generally supplied as (NH4)2SO4 • Protein and peptides can be utilized if the microbes are able to hydrolyze • Yeast extract function??

  6. Microelements • Ca, Mn, Fe, Cu, Co and Zn are essential • B, Cr and Mo are rarely required • Commonly added as mineral salts • Trace elements deficiencies in batch cultures are reflected by limitation of the growth rate • In continuous culture, by the decrease observed in the steady state biomass conc. • Must consider the interactions because optimum conc of any ion is dependent on the conc of the others.

  7. Growth Factors • Some microbes require specific nutritional factors which they cannot synthesize - growth factors • 3 groups – vitamins, amino acids and miscellaneous compounds • Water soluble vitamins – mostly coenzymes • In complex media, eg cane molasses already contain several vitamins

  8. Other Additives • Precursors, egphenylacetic acid in penicillin biosynthesis • Stimulants, eg methanol in citric acid production • Protectants • Antifoams • Chelators – eg EDTA • Stabilizers – to avoid the loss of plasmids • Neutralizing agent – eg. Phosphate buffers

  9. Influence of Physical Factors • Temperature and water activity • Eg. To grow S.cereviciaeat 37C instead of 30C, the pantothenic acid content must be increased. • Pasteurellapestisrequires more amino acids and vitamins for growth at 37C than at 28C.

  10. The medium selected will affect the design of the fermenter to be used. • A laboratory medium may not ideal in a large fermenter with a low gas-transfer pattern. • Media with a high viscosity will also need a higher power input for effective stirring. • Besides the requirement for growth and product formation, medium may also influence pH variation, foam formation, oxidation-reduction potential and the morphological form of the organisms. • It may also be necessary to provide precursors or metabolic inhibitors.

  11. Guide to Design and Formulation for Plant Cell Suspension Media • The use of two-step process, first using a growth medium and second, a production medium • C source – sucrose is preferred. • Add phytohormones to improve yield or productivity • Adding precursors to enhance secondary metabolite formation

  12. Growth Medium • Select a basal medium such as MS, B5 or other • Test the medium in shake flasks and in a bioreactor and optimize it for maximal biomass production

  13. Production Medium • Maintain the same carbohydrate conc of the growth media and then test the following: • Reduce the phosphate and nitrogen content • Modify the vitamins and iron (chelated) content • Find adequate phytohormones level and their ratios • Add a precursor and find the correct time for its addition • Test a biotic or an abiotic elicitor • Optimize the medium by fractional factorial statistical methodology

  14. Large Scale Media • Take into account: - fermenter size - fermentation time - purification procedure - medium composition before implementation!!

  15. Can you detect the differences between plant and animal culture media?

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