2. Sterilization -
• It is a process of destruction or removing of all
forms of living micro organisms from a
substance or surface by treating it with
chemicals, radiations or by steam.
3. Air Sterilization -
• Methods of air sterilization –
i. Sterilization by heating
ii. Radiations
iii. Use of chemicals
iv. Sterilization by filtration
• Filtration sterilization method is commonly
used.
4. Filtration -
• Two types of filtration –
i. Depth Filter
ii. Absolute Filter
i. Depth Filter –
• Also called non-fixed pore filter.
• In this when air is passed through a glass
wool containing depth filters the particles are
trapped & removed.
5. ii. Absolute Filter –
• Also called fixed pore filters.
• These are removable pleated membrane filter
made up of cellulose ester or nylon.
• They are smaller in size, simpler for
operation & replacement.
6. Media Sterilization -
• In- situ – fermentor vessel & fermentation
medium is sterilize at a time.
• Ex- situ – fermentor vessel & fermentation
medium is sterilize separately & then add.
7. Methods of Media Sterilization -
i. Heat sterilization
ii. Sterilization by filtration
iii. Radiations
iv. Use of Chemicals
i. Heat sterilization –
Most widely used sterilization technique.
8. a) Direct Heating –
• Boiling
b) Steam –
• Batch Sterilization –
o It is done by injecting the steam into the
medium or injecting into interior coils
o Culture media are subjected to sterilize at
120°C in batch volume.
9. • Continuous Sterilization -
o It is done by directly injecting the steam or by
means of heat exchangers.
o It is carried out at 140°C for 30- 120 seconds.
o Three types of heat exchangers -
I. 1st at 90-120°C within 20-30 seconds
II. 2nd at 140°C maintains 30-120 seconds
III. 3rd bring down temperature by cooling into
20-30 seconds
10. • Autoclave -
o The process is carried out at a temperature of
121°C for 20 minutes at 15psi pressure.
11. ii. Filtration -
• It is the quickest way of sterilization without
heating.
• Membrane filters are more commonly used.
• It may be noted that viruses & phage are
much smaller than bacteria so the filtration
method is not applicable.
12. iii. Radiations -
• This method involves exposing the packed
materials to radiations for sterilization.
• Two types of Radiations –
I. Non- ionic Radiation-
• UV rays have low penetration & thus are less
effective.
• But it is relatively safe & can be used for
small area sterilization.
13. II. Ionic Radiation –
• X-ray & Gamma rays have more penetrating
power, thus more effective for sterilization on
a large scale.
14. iv. Chemical Agents -
• This is done by using toxic gasses.
• Gasses used for sterilization are very
poisonous.
• The commonly used gas is Ethylene oxide
with a combination of carbon dioxide.
• Other gasses like hydrogen peroxide, ozone
also used.
