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Components of a typical fermentor
A specially designed vessel in which large quantity fermentation media is added with fermentation microorganisms which provides best possible environment control and process control for the biosynthesis of fermentation products.

Each components of the fermentor serve a specific purpose with proper arrangement for aeration, temperature and pH control, and drain or overflow vent to remove the waste biomass of cultured microorganisms along with the fermented products.

A bioreactor or a fermentor should provide for the following basic functions:-
 * 1) Agitation for mixing of cells and fermentation medium.
 * 2) Aeration for the supply of oxygen (O2)
 * 3) Regulation of factors like temperature, pH, pressure, aeration, nutrient feeding, liquid level.
 * 4) Withdrawal of cells/medium.

Major parts of a fermentor

 * Material used for fermentor
 * Baffles
 * Impellers
 * Inoculation port
 * Spargers
 * Sampling point
 * Temperature control device
 * pH control device
 * Foam control device/system
 * Bottom drainage system

Material used for fermentor
The material used for the fermentor should have some important functions. The materials used for construction of a bioreactor or a fermentor should be resistant to corrosion and should not add any toxic substances to the fermentation media. Moreover, the material used should have the ability to tolerate the steam sterilization proccess and high pressures. The material used should also be resistant to changes in the pH.

The fermentor material also largely depends upon the type of fermentation proccess that is carried out. In case of beer, wine, lactic acid fermentation fermentors made of wooden material are usually used. In some rare cases, stainless steel, iron, copper and glass are used. Mostly 314 or 316 stainless steel are used in making fermentors. These fermentors are mostly coated with glass or epoxy lining.

The material used should be such that the fermentor should regulate and monitor various fermentation processes and reactions.

Impellers
It is a device in the fermentation used for agitation. It is mounted on the shaft and are introduced into the vessel through its lid.They are made up of impeller blades and its position of attachment may vary with the function. These impellers are attached to a motor which facilitates its movement. They mix the micro-organisms, oxygen and the fermentation media uniformly. The impellers reduce the size of air bubbles and distribute them uniformly into the fermentation media. It can also help in reduction of foam contamination by breaking the foam bubbles in the head space of the fermentor.

Types of impellers
In industrial scale bioreactors, there are three types of impellers that can be used. They are:-
 * Disc Turbine:- It consists of a disc with a series of rectangular vanes connected in a vertical plane around the disc.
 * Vaned disc :- It consists of rectangular vanes attached to the underside of the disc.
 * Variable Pitch Open Turbine:- It lacks disc and the vanes are directly connected to the central shaft.

Baffles
They are mounted onto the walls of the fermentor. Their main function is to break the vortex formed by the impellers during the fermentation process. The breakdown of the vortex is integral to the fermentation process as there can spillage of the fermentation media if the vortex is not broken down, resulting in contamination of the fermentation media. Baffles acts as barriers which breaks the vortex.

Inoculation port
It is a device from which the inoculum, fermentation media and the substrate are added to the fermentation vessel. The inoculation port in a good fermenter must be easy to sterilize. The inoculation port should only provide aseptic transfer of the components used for the fermentation process.

Spargers
An aeration system through which sterile air is introduced in the fermentation tank. They are located at the bottom of the fermentation tank. Glass wool filters are used in spargers for the sterilization of air and other gases. These devices contain small holes measuring from 5 to 10 mm through which pressurised air is released into the media. The air is released into the media in the form of bubbles which help in mixing the media. There are different types of spargers available that are used in fermentation tanks.

Types of spargers:-
Porous sparger:- made of ceramics, metal or sintered glass. The size of bubble will be 10 to 100 times the pore size of the sparger. There is a pressure drop across the sparger and the holes tend to be blocked which is the limitation of a porous sparger.

Orifice sparger:- It is a perforated pipe kept below the impeller in the form of crosses or rings. The size should be 3/4th of the size of the impeller. Air holes are drilled on the inner surfaces of the tube and each of them are 6mm in diameter. It is used mostly with agitation.

Nozzle sparger:- It is mostly used in large scale fermenters. It is a single open or partially closed pipe positioned central below the impeller. There is lower pressure loss so that the air flow does not get blocked.

Combined sparger agitator:- The air is emitted through holes of a disc or the blades of an agitator.

Sampling point
It is used to withdraw the fermentation sample aseptically to maintain the quality of the mixture in the fermentation tank.

pH control device
This device monitors the pH of the media in the fermentation tank and controls aand regulates the pH with the help of acid- base reservoirs. The acid- base reservoirs decrease or increase the pH by adding acid or base respectively.

Temperature control system
The temperature control system consists of thermometers and cooling coils or jackets around the fermentor. During the fermentation process, heat is generated in the media. This increase in temperature can retard the fermentation process as this prevents the growth of microorganisms in the fermentor. Therefore it is important to regulate the temperature of the fermentation media. The temperature regulation is facilitated by the passing of cool water through the coils or jackets around the fermentor.

Foam Control Device
This device is placed onto the top of the fermentor and has an inlet into the tank containing the fermentation media. This device contains a small tank containing anti-foaming agent. During the fermentation process some amount of foam is formed. It is very important to remove this foam formed with the help of this anti-foaming agent. The foam formed can block or reduce the speed of the impeller hence affecting the fermentation process. The foam can also result in spillage of the media and can cause contamination.

Types of Antifoaming agents that are used in fermentors:-
It does contain mineral oils and can be used as good surfactants.
 * Organic Antifoams :- Antifoam 204 contains 100% active components and is a mixture of non-organic silicon polypropylene based polyether dispersions.


 * Silicone Antifoams:- The active ingredient of these antifoams are silicon based polymers that have a molecular weight range from 3,200 to 16,500 Da. They consists of particles ranging from 10 to 40 microns which can be removed by filtration. They are present in the form of suspensions and should be agitated before treating with the sample taken from the container.

Bottom drainage system
It is an outlet present at the bottom of the fermentor. This is an aseptic outlet through which the fermented products and the fermentation media are removed.