Sterilization of Fermentation Media
Sterilization of fermentation media play a important role in fermentation .If the fermentation media is not sterilized properly or we can say if the media gets contaminated it can lead to economic loss.The contamination of media can effect the yield of product,it can change the product or it can effect the growth of fermentation organism.So it is very important to sterilise the fermentation media properly.
There are different techniques used to sterilise different types of media as well as different nutrient supplies used in fermentation .Depending on the necessity the sterilization techniques are used..Fermentation techniques are carried out in Laboratory scale as well as Industrial Scale .
Sterilisation of fermentation media is done by Autoclaving, Boiling, or passing steam through media.The synthetic media can be sterilized in short time where as crude media requires more time for sterilization. Sterilization method used is decided on basis of type and characteristic of media components.
Crude media is more viscose and it may contain spores or highly resistant bacteria so the time required for sterilization is more.Where as crude media contain high sugar content so it should be sterilized properly because if high amount of heat is passed for longer duration of time through media it may caramelise sugar sugar content of media and result in spoilage of media.
The fermentation media which contains substances that can undergo chemical changes as well as degradation due to heat such fermentation media is sterilised by filtration. Some fermentation media contains vitamins,enzymes and volatile components in media get destroyed easily by heat.So such media component should be sterilized using bacteriological filters.
Generally fermentation media is sterilized by autoclaving that is sterilization of media steam under pressure.If fermentation media is in large amount the fermentation batches are passed through heat retention tubes containing jet heaters.So the type of fermentation depends upon type of fermentation media and type of components present in it.
Design of Fermentation Media
In a fermentation process, the choice of the most optimum micro-organisms and fermentation media is very important for high yield of product. The quality of fermentation media is important as it provides nutrients and energy for growth of micro-organisms. This medium provides substrate for product synthesis in a fermentor.
Fermentation media consists of major and minor components.
- Major components include Carbon and Nitrogen source.
- Minor components include inorganic salts, vitamins, growth factors, anti-foaming agents, buffers, dissolved oxygen, other dissolved gases, growth inhibitors and enzymes.
Nutrients required for fermentation media also depend upon the type of fermentation organisms as well as the type of fermentation process to be used. Poor choice of fermentation media might result in poor yield of output. Types of nutrients present in the fermentation media always determine the yield of the product.
There are two uses of fermentation media
- Growth media
- Fermentation media
Growth medium contains low amounts of nutrients.It is useful in creating raw material for further fermentation processes.
Fermentation media contains high amounts of nutrients. It is used in creating final products using fermentation.
For example, growth of yeast requires 1% carbon. But during fermentation of alcohol, yeast requires 12 to 13 % carbon in the medium.
There are three types of fermentation processes and they are
- Batch fermentation
- Continuous fermentation
- Dual or multiple fermentation
- 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.
- 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
Design of a Fermentor
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.