Fermentation

(Def, Applications, steps, General requirements, fermenter –design & accessories, materials of body construction, aeration & agitation)

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• Fermentation is the process in which a substance breaks down into a simpler substance by microorganisms like yeast and bacteria.
•  Fermentation is a metabolic process that converts sugar to acids, gases or alcohol.
• It occurs in yeast and bacteria, but also in oxygen-starved muscle cells, as in the case of lactic acid fermentation.
• Fermentation is also used more broadly to refer to the bulk growth of microorganisms on a growth medium, often with the goal of producing a specific chemical product.
• The science of fermentation is known as zymology

Applications of Fermentation Process:

1. To Produce Microbial cells or Biomass ex: yeast cells, single cell proteins.
2. To Produce Microbial Enzymes bacterial : amylase, protease, lipase Fungal: pectinase, amylase, protease.
3. To Produce Microbial Metabolites -

➔Primary metabolites: produced during log phase of growth and are essential for growth of microbes  Ex: glutamic acid, lysine, vitamins and proteins.

➔Secondary metabolites: produced during idio phase of growth and not essential for growth of microbes Ex: antibiotics, inhibitors.

4.    To Produce Recombinant Products hormones:

➔Growth hormone, insulin Therapeutic proteins: interferons.

5.    To modify a compound which is added to the fermentation (biotransformation) prostaglandins, steroidal drugs.

Steps to carry out a Fermentation:

1.  The formulation of media to be used in culturing the process organism during the development of the inoculum and in the production fermenter.
2. The sterilization of the medium, fermenters and ancillary equipment.
3. The production of an active, pure culture in sufficient quantity to inoculate the production vessel.
4. The growth of the organism in the production fermenter under optimum conditions for product formation.
5. The extraction of the product and its purification.
6. The disposal of effluents produced by the process.

General requirements of fermentation production:

1. Fermenter,

2. Fermentation medium,

3. Microbial sources,

4. Sterilization,

5. Provisions for control parameters,

6. Provisions for Recovery & purification,

7. Provisions for waste disposal.

Fig: Fermenter

Fig:- Various components of an ideal fermenter for batch process.

Fig: Monitoring and controlling parts of fermenter.

Basic Functions of a Fermenter:

• The vessel should be capable of being operated aseptically for a number of days and should be reliable in long-term operation and meet the requirements of containment regulations
• Adequate aeration and agitation should be provided to meet the metabolic requirements of the micro-organism. However, the mixing should not cause damage to the organism. • Power consumption should be as low as possible.
• A system of temperature control should be provided.
• A system of pH control should be provided.
• Sampling facilities should be provided.
• Evaporation losses from the fermenter should not be excessive.

• The vessel should be designed to require the minimal use of labor in operation, harvesting, cleaning and maintenance.

• Ideally the vessel should be suitable for a range of processes, but this may be restricted because of containment regulations. 

• The vessel should be constructed to ensure smooth internal surfaces, using welds instead of flange joints whenever possible.

• The vessel should be of similar geometry to both smaller and larger vessels in the pilot plant or plant to facilitate scale-up.

• The cheapest materials which enable satisfactory results to be achieved should be used.

• There should be adequate service provisions for individual plants.

Materials for Body Construction of a Fermenter:

• In fermentations with strict aseptic requirements it is important to select materials that can withstand repeated steam sterilization cycles.

• On a small scale (1 to 30 lit) it is possible to use glass and/or stainless steel.

• Glass is useful because it gives smooth surfaces, is non-toxic, corrosion proof and it is usually easy to examine the interior of the vessel.

• A glass cylinder with stainless-steel top and bottom plates.

• At pilot and large scale, when all fermenters are sterilized in situ, any materials used will have to be assessed on their ability to withstand pressure sterilization and corrosion and on their potential toxicity and cost.

• Pilot scale and Industrial scale vessels are normally constructed of stainless steel or at least have a stainless-steel cladding to limit corrosion.

• Mild steel coated with glass or phenolic epoxy materials has occasionally been used.

• The minimum amount of chromium needed to resist corrosion will depend on the corroding agent in a particular environment, such as acids, alkalis, gases, soil, salt or fresh water.

• Increasing the chromium content enhances resistance to corrosion, but only grades of steel containing at least 10 to 13% chromium develop an effective film.

• The inclusion of nickel in high percent chromium steels enhances their resistance and improves their engineering properties.

• The presence of molybdenum improves the resistance of stainless steels to solutions of halogen salts and pitting by chloride ions in brine or sea water.

• Corrosion resistance can also be improved by tungsten, silicone and other elements.

• It is important to consider the ways in which a reliable aseptic seal is made between glass and glass, glass and metal or metal and metal joints such as between a fermenter vessel and a detachable top or base plate.

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