This document discusses sterilization of air and media. It defines sterilization as removing microorganisms through chemicals, heat, or radiation. For air sterilization, common methods are heating, radiation, chemicals, and filtration. Filtration uses depth or absolute filters to trap particles. Media sterilization can be in-situ or ex-situ. Common media sterilization methods are heat (such as autoclaving or steam), filtration, radiation (ionizing or non-ionizing), and chemicals (like ethylene oxide gas). Heat sterilization via autoclaving is most widely used.

1. Air and Media Sterilization
Yogesh Bhandari

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.

15. Thank You