Overview of bioreactor or fermenters

Contents

• Introduction
• History
• Function
• Design
• Classifications

Introduction

• It is a device or system that used to support biologically active environment.
• It is a system within which substrate of very low value is employ by living cells or enzymes to produce a product of greater value.
• A fermenter is a closed system vessel which have an adequate provision for temperature, agitation, aeration, pH control, and drain or overflow vent to remove waste biomass of culture microorganism with their products.

History

• In 1944 De becze and Liebmann used the primary large-scale fermenter for the growth of yeast.
• But, during the time of world war there’s is a British scientist whose name is Chain Weizmann who desigined a fermenter for the production of acetone.

Functions

• It should have a provision to control environment for optimum biomass or product yield.
• It should provide an aseptic fermentation condition for more reliablity.
• It should provide the adequate or proper mixing and aeration for the growth and production without damaging of the microorganisms or cells.
• It should have a system temperature control.
• It should have a system to monitor and regulate pH of the fermentation broth.
• Facility for sampling should be provided.
• It should have required minimum of labour in maintenance, cleaning, operating and harvesting operation.

Design

A bioreactor should consist of the followings:

1. Agitation- for mixing of cells and medium.
2. Aeration – aerobic fermentation used for oxygen supply.
3. Temperature
4. pH, pressure, nutrients feeding, etc.
5. Sterilization and maintenance of sterility.
6. Withdrawal of cells or media.

Agitation and Aeration

• Agitations are aims to ensure similar distribution of microorganisms and the nutrients in the broth.
• Aeration to provide microorganisms growing in submerged culture with adequate oxygen supply.

The following components of the fermenter which is required for aeration and agitation:

1. Agitator (impellers)
2. Stirrer glands and bearings
3. Baffles
4. Sparger (the Aeration system)

Agitator (Impellers)

• It is of several different type:

1. 1. Disc turbine
   2. Vaned disc turbine
   3. Open turbine
   4. Propeller

• It achieves the following objective:
  1. Bulk mixing
  2. Air dispersion
  3. Oxygen transfer
  4. Heat transfer
  5. Maintain uniform environment

Stirrer glands and bearings

• It provides for maintaining aseptic conditions over a long period.

Four basic types of seals used in fermenters are:

1. 1. Stuffing box
   2. Simple bush seal
   3. Mechanical seal
   4. Magnetic drive

Baffles

• It is metal strips.
• One tenth of the vessels diameter.
• Attached radially to fermenters wall.
• It provided to prevent vortex formation and improve efficiency.

Aeration system (Sparger)

• It introduces air into the fermenters broth.

It is of three types:

1. 1. Porous Sparger
   2. Orifice Sparger
   3. Nozzle Sparger

Temperature control: adequate provision for control of Temperature.

Pressure gauge: It measures pressure inside the fermenters.

pH probe: It provides to measure and monitor pH of the medium.

Inlet air filter: Provision to supply air in the fermenters.

Exhaust air filter: Provision to drain out the air from the fermenters.

Cooling jacket: Provided to maintain the temperature of the fermenters throughout the process.

Control panel: it monitors all the parameters.

Foam control: it is produced during most microbial fermentation. Antifoams are used to removes foam from the surface of media e.g., silicone, soybean oil, cotton seed oil, sulphonate etc.

Classifications

• On the basis of agent used, bioreactors are of two types:

1. 1. On the basis of living cells
   2. On the basis of enzymes employed

• In the terms of process fermenters, is of following types:

1. 1. Aerobic
   2. Anaerobic
   3. Solid state
   4. Immobilized cell disruption

Types of fermenters

• Fermenters are of 4 types:

1. 1. Stirred tank reactor
   2. Airlift fermenters
   3. Tower fermenters
   4. Bubble up fermenters

Stirred tank reactor

• Smaller vessel is made up of glass while, lager vessels are made up of stainless steel of 1-1,000 or even 8,000L.
• They are closed system in which volumes are fixed.
• They are agitated with motor driven stirrer’s.
• It is a kind reactor with continuous flow culture system which is either of chemostat or turbidostat type.

Airlift fermenters

• It comprises of a gas light baffled riser tube or drought tube which is connected to the downcomer tube.

It is of two types:

1. 1. Internal- loop airlift bioreactor
   2. External loop airlift bioreactor

• These type of fermenters are commonly employed for aerobic bioprocessing technology.
• Because of their high efficiency, it is mostly preferred for production of methanol and SCP, etc.

Tower fermentation

• It was defined by Greenshields and co-workers.
• It is an elongated non-mechanically type of fermenters.
• There is unidirectional gases flow throughout the bioreactors.

Tower fermenters are of following types:

1. 1. Bubble columns
   2. Vertical tower beer fermenters
   3. Multistage fermenters

Bubble up fermenters

• It is a bubble columns fermenters which havee an internal cooling coil.
• Air is introduced from the bottom of the column.

Reference and Sources

• 1% – https://wiki2.org/en/Bioreactor
• 1% – https://samacheerkalvi.guru/author/bhagya/page/9/
• 4% – https://www.slideshare.net/shmpanwar92/bioreactors-fermenters-56475754
• 2% – https://senthilarivan.wordpress.com/2015/11/26/fermenter-and-its-features/
• 1% – https://www.dedot.info/airlift-fermenters-17/

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Overview of bioreactor or fermenters