Design of a Fermentor | Industrial Microbiology

Design of a Fermentor

Fermentation

Fermentation can be defined as a metabolic process in which cheap raw materials such as sugar or carbohydrates are converted into economically important products like acids, gases and alcohols by micro-organism. This process is carried out in a equipment called as fermentor.

What is a Fermentor?

A Fermentor can be defined as a vessel in which sterile nutrient media and pure culture of micro-organism are mixed and fermentation process is carried out under aseptic and optimum condition.

Fermentor provides a sterile environment and optimum condition that are important for growth of micro-organisms and synthesis of desired product.

Design of Fermentor

A fermentor should be constructed in such a way that it can make provisions for the below activities:

  • Sterilization
  • Temperature control
  • pH control
  • Foam control
  • Aeration and agitation
  • Sampling point
  • Inoculation points for micro-organisms, media and supplements
  • Drainage point for drainage of fermented media
  • Harvesting of product
  • Cleaning
  • Facility of providing hot, cold water and sterile compressed air.

Here one by one we will be studying major parts of fermentor and their function.

  1. Material used for fermentor
  2. Impellers
  3. Baffles
  4. Inoculation port
  5. Sparger
  6. Sampling point
  7. pH control device
  8. Temperature control system
  9. Foam control device
  10. Bottom drainage system

Here is a flow chart that shows major parts of fermentor.

Major parts of Fermentor

  1. Material used for fermentor

The material used for designing of a fermentor should have some important functions.

  • It should not be corrosive
  • It should not add any toxic substances to the fermentation media.
  • It should tolerate steam sterilization process.
  • It should be able to tolerate high pressure and resist pH changes.

The fermentor material used is also decided on type of fermentation process. For example, in case of Beer, Wine, Lactic acid fermentation, the fermentor tanks are made up of wooden material. Whereas material such as iron, copper, glass and stainless steel can be used in some cases. Most of the time, 304 and 316 stainless steel is used for designing of a fermentor and these fermentors are mostly coated with epoxy or glass lining.

A fermentor should provide the facility to control and monitor various parameters for a successful fermentation process.

2. Impellers

  • Impellers are an agitation device. They are mounted on the shaft and introduced in the fermentor through its lid.
  • They are made up of impeller blades and the position may vary according to its need.
  • These impellers or blades are attach to a motor on lid.
  • The important function of an impeller is to mix micro-organisms, media and oxygen uniformly.
  • Impeller blades reduce the size of air bubbles and distributes these air bubbles uniformly into the fermentation media.
  • Impellers also helps in breaking foam bubbles in the head space of fermentor. This foam formed during fermentation process can cause contamination problem and this problem is avoided by the use of impellers.

3. Baffles

  • Baffles are mounted on the walls of a fermentor.
  • The important function of baffles is to break the vortex formed during agitation process by the impellers.
  • If this vortex is not broken, the fermentation media may spill out of fermentor and this may result in contamination as well as can lead to different problems. So it is important to break the vortex formed by using a barrier.
  • Baffles acts as a barrier which break the vortex.

4. Inoculation Port

  • Inoculation port is a device from which fermentation media, inoculum and substrate are added in the fermentation tank.
  • Care should be taken that the port provides aseptic transfer.
  • The inoculation port should be easy to sterilize.

5. Spargers

  • A Sparger is an aeration system through which sterile air is introduced in the fermentation tank.
  • Spargers are located at the bottom of the fermentation tank.
  • Glass wool filters are used in a sparger for sterilization of air and other gases.
  • The sparger pipes contain small holes of about 5-10 mm. Through these small holes pressurized air is released in the aqueous fermentation media.
  • The air released is in the form of tiny air bubbles. These air bubbles helps in mixing of media.

6. Sampling point

  • Sampling point is used for time to time withdrawal of samples to monitor fermentation process and quality control.
  • This sampling point should provide aseptic withdrawal of sample.

7. pH Control device

  • The pH controlling device checks the pH of media at specific intervals of time and adjusts the pH to its optimum level by addition of acids or alkalis.
  • Maintaining pH to its optimum level is very important for growth of micro-organism to obtain a desired product.

8. Temperature control

  • Temperature control device generally contains a thermometer and cooling coils or jackets around fermentor.
  • During the fermentation process, various reactions take place in the fermentor. Heat is generated and released in the fermentation media. This increase in temperature is detrimental to the growth of micro-organisms, which may slow down the fermentation process.
  • So, it is necessary to control this rise in temperature. This is done by passing cool water through the coils or jackets present around fermentor.

9. Foam controlling device

  • A Foam controlling device is placed on the top of fermentor with a inlet into fermentor. This device contains a small tank containing anti-foaming agent.
  • Foam  is generated during fermentation. It is necessary to remove or neutralize this foam with the help of anti-foaming agents, lest the media may spill out of fermentor and lead into contamination and a mess.

10. Bottom drainage system

  • It is an aseptic outlet present at the bottom of fermentor for removal of fermented media and products formed.

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