Types of Fermentation Processes | Industrial Microbiology

There are three types of fermentation processes and they are

  1. Batch fermentation
  2. Continuous fermentation
  3. Dual or multiple fermentation
  1. Batch fermentation

Batch fermentation is carried out in batches. Here, fermentation media is filled up to 80% space by fermentor, and the remaining space is used as head space. Head space plays an important role as some area of a fermentor is required for collection of air, gases, and foam which is produced during the fermentation process. Further, after inoculation of media the fermentor is steam sterilized and after sterilization, the nutrient media is cooled and inoculated with desired volume of inoculums under aseptic condition.

Fermentation process is carried out under optimum growth condition. It is stopped after specific period of time and the fermented media or broth are removed from the fermentor and the desired product is obtained.

The product obtained is passed through recovery and purification process. Later, the fermentor is cleaned and reused for the next batch. In this process, as the fermentation proceeds, the quantity of nutrients from the media gets depleted, and microbes and products increase. In batch fermentation, growth of micro-organism is slower down due to decrease of nutrients.

Advantages of batch fermentation

It requires less space, there are fewer chances of contamination and this process is easy to handle. The disadvantage is that it is a time consuming process and it requires more time for cleaning, sterilization, cooling. The yield of the product is also low.

  1. Continuous fermentation process.

In continous fermentation process fermentation runs continuously without emptying of fermentation tank. It involves continous addition of fresh media and withdrawal of fermentation media is constant.Each and every cell in fermentation media should be in log phase and not in stationary phase.The rate of addition of media should satisfy nutrient requirement of fermentation organism if rate of addition of media is slow there are chances that cells enter in stationary phase.There are three types of continuous fermentation processes.

i] Single stage continuous fermentation

ii] Single stage recycle continuous fermentation

iii] Multi-stage continuous fermentation


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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


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Fermentation Equipment and its Application

  • Fermentation can be defined as a metabolic process in which raw materials such as sugar or carbohydrates are converted into acids, gases and alcohols. Micro-organisms such as yeast and bacteria play a central role in the fermentation process.
  • Fermentation process requires a fermentor, substrate, inoculum and optimum conditions.
  • The equipment used to carry out fermentation is called a fermentor.
  • A fermentor can be defined as an equipment or a vessel in which fermentation process is carried out.
  • A fermentor is a complex machine. It is used to create optimum conditions that are necessary for the fermentation process.

 Design of a fermentor

  1. A fermentor should be large enough to allow creation of fermentor bacteria.
  2. The material used in the manufacture of a fermentor should be strong enough to tolerate the pressures of fermentation media and gases produced.
  3. The material should be non-corrosive.
  4. It should not contribute toxic ions or substances to the fermentation media, because these toxic ions can harm the growth of microbial culture.
  5. It should have an inlet for oxygen and outlet for carbon dioxide in case aerobic microbes are used for fermentation.
  6. It should be completely sealed from outside environment to avoid contamination.
  7. It should be easily sterilize.
  8. It should provide a facility to add anti-foaming agents as well as a temperature controlling system.
  9. A pH detecting system is also important. An outlet for the withdrawal of media for determination of pH as well as inlet for addition of acids and alkalis should be provided. It is important to maintain pH at optimum levels for growth of culture.
  10. The most important thing is that a fermentor should provide aseptic means of withdrawal of fermented product and introduction of culture samples.
  11. The fermentor facilitate the stirring of media so that inoculum and fermentation media mix properly. It also ensures that the gases required for growth of microbial culture are available to all microbes.

Types of Fermentors and its Uses

1. Laboratory Scale fermentor

  • It is the smallest type of fermentor.
  • Capacity of this fermentor is minimum one to two litres and maximum up to twelve to fifteen litres.
  • It is used for research and development purposes.
  • Laboratory scale fermentor is used for determination of optimum condition of growth and biosynthesis of micro-organism.

2. Pilot scale fermentor

  • Pilot scale fermentor are of intermediate size.
  • It is used in large scale studies of fermentation process.
  • The minimum size range is of 25 to 100 gallons that is 94 litres to 378 litres.
  • The maximum size range is 2000 gallons that is 7570 litres.

3. Industrial scale fermentor

  • Industrial fermentor is a large scale fermentor. It is used in industries for fermentation of industrially important product.
  • The minimum size range is 5000 gallons to 10,000 gallons that is 18927.06 litres to 37854.12 litres.
  • The maximum size range 10,0000 gallons that is 378541.18.

This was the overview of fermentor and important aspects that are considered under fermentation process but there are important aspects that are carried out during fermentation process.

  1. Media formulation
  2. Inoculum preparation
  3. Sterilization of nutrient media and preparation of media.
  4. Fermentation process
  5. Recovery
  6. Purification
  7. Waste disposal

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Introduction to Industrial Microbiology

Industrial microbiology is a branch of science that deals with the study and uses of micro-organism which have industrial and economic applications. In industrial microbiology, microbes classified, characterized are isolated from their natural environment. Further, these micro-organism are produced on a large-scale by use of a fermentor.

Fermenting tanks with yeast being used to brew beer. Photo by Kafziel

Modern Fermenting Tanks
Photo by Kafziel

The most important applications of industrial microbiology are using microbes to convert inexpensive raw materials into economically important products. Further, these products go through detection, analysis, assay, purification and recovery to make them safe and effective. The end products are valuable, but the microbes creating these products are equally important.

During the process of industrial fermentation, microbial cells produce extra-cellular as well as intra-cellular enzymes. These enzymes play an important role in fermentation, degradation and utilization of media components. Enzymes can be used as a product by itself and have many end use applications. For example, enzymes like amylase and proteases are used in a variety of products.
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