1. Batch & Continuous sterilization
techniques:
By
Harinatha Reddy A
Christ University
Department of Biotechnology
biohari14@gmail.com
2. Batch sterilization:
Batch sterilization can be done by injecting the steam into the medium or
direct electrical heating of medium.
The culture media are subjected to sterilization at 121°C, in the bioreactor for
20-60 minutes.
For the direct batch sterilization, the steam should be pure, and free from all
chemical additives.
3. Batch sterilization is the reduction of contaminant organisms.
The batch sterilization, a system goes through 3 steps:
Heating, Holding, and Cooling.
4. The temperature is increased until it reaches the sterilization
temperature where it is held for a set period of time.
During this phase, most of the unwanted microorganisms are
destroyed.
Finally, the system is cooled to bring the sterile media back to
the desired temperature.
5. There are two disadvantages of batch sterilization:
1. Damage to culture media:
Alteration in nutrients, change in pH and discolouration of the
culture media are common.
2. High energy consumption:
All this process involves wastage of energy, and therefore batch
sterilization is quite costly.
8. Continuous sterilization is carried out at 140°C for a very short
period of time ranging from 30 to 120 seconds.
This is based on the principle that the time required for killing
microorganisms is much shorter at higher temperature.
9. In Continuous sterilization the culture medium continuously
pumping holding loop.
Once the media is in a holding loop, steam is injected to the
system via a nozzle.
The sterile culture medium again pumped into the flash cooler to
bring culture medium to normal temperature.
11. Advantages of continuous sterilization:
3. This process involves less wastage of energy, and
because sterilization complete with in short period.
4. Low risk of contamination.
12. Disadvantages:
The certain chemical compounds in the medium become
precipitated (e.g., calcium phosphate, calcium oxalate) due to very
high temperature.
The starch-containing culture media becomes viscous in
continuous sterilization and therefore is not used.
13. Sterilization of Air:
Industrial fermentations are carried out under continuous
aeration.
Air can be sterilized by filtration, heat and UV radiation.
14. Air sterilization by heat:
In the early years, air was passed over electrically heated elements
and sterilized.
But this is quite expense, hence not in use these days.
15. Air sterilization by filtration:
Filtration of air is the most commonly used sterilization in
fermentation industries.
Depth filters:
Membrane cartridge filters:
16. Depth filters:
When the air is passed through a glass wool (fibrous) containing
depth filters the particles are trapped and removed.
The air is pass through this depth filter the microbial cells are
removed by physical screening or entrapment.
17. Membrane cartridge filters:
Membrane filters made up of cellulose ester or nylon.
Membrane cartridge filters are smaller in size, simpler for operation
and replacement.
Membrane cartridge filters has capability to remove Bacteriophages
form air.