The document discusses various sterilization methods including thermal (dry and moist heat), radiation, filtration, and chemical. It provides details on key sterilization techniques such as autoclaving, which uses pressurized steam to achieve high temperatures for sterilizing materials. The document also defines important sterilization terms and concepts like D-value, which is the time required to reduce microbial counts by 90%. Overall, the document provides a comprehensive overview of common sterilization procedures and their mechanisms of action to eliminate microorganisms.

1. By :- Siddharth Kumar Sahu

2. • Sterilization and Terminologies
• Thermal Resistance of Micro-organism.
• Methods of sterilization
• Dry Heat Sterilization.
• Moist Heat Sterilization
• Radiation Sterilization.
• Filtration Sterilization.
• Chemical Method of sterilization.
• Gaseous Sterilization.

3. • Sterilization can be defined as any process that effectively kills or
eliminates transmissible agents (such as fungi, bacteria, viruses and
prions) from a surface, equipment, foods, medications, or biological
culture medium.
OR
• Sterilization refers to any process that eliminates, removes, kills, or
deactivates all forms of life and other biological agents like prions
present in a specific surface, object or fluid, for example food or
biological culture media.
OR in short.....
• It is a process of complete destruction of all microorganisms present in a
system and the products free from living organisms are called Sterile

4.  Disinfection: it is a process that eliminates many or all pathogenic
microorganisms, except bacterial spores.
o Different disinfectants have different target ranges, not all
disinfectants can kill all microorganisms.
 Antiseptic: not a disinfectant. It is a substance or product which
prevent the growth of microorganisms by inhibiting their activity
without destroying them.
 Sanitization: A process that reduces the level of micro organisms
count on eating and drinking utensils.

5.  Decontamination: Decontamination removes pathogenic
microorganisms from objects so they are safe to handle, use,
or discard.
 Aseptic: Free from contamination caused by harmful bacteria,
viruses, or other microorganisms; surgically sterile or sterilized.
 Aseptic processing is a processing technique where
thermally sterilized liquid products (typically food
or pharmaceutical) are packaged into previously sterilized
containers under sterile conditions to produce shelf-stable
products that do not need refrigeration.

6. • Heat(thermal) is lethal to microorganisms, but each species has
its own particular heat tolerance. And resistant of heat is varies
according to the method of sterilization.
• Before selecting any method for sterilization , first know the
condition & method that must be lethal to microorganisms &
spores. So, following points should be note…
1. Thermal Death Time
2. Death Rate of Microorganisms
3. Decimal Reduction Time ( D Value)

7. • It is defined as the time required to kill a specific micro-
organisms at a given temperature under specific
condition.
• Thermal death time depends on factors like-
I. Temprature
II. pH
III. Presence of Bactericide
IV. No. of Microorganisms
V. Resistance to Heat.
The rate at which a given microbe dies from treatment is
constant, but the time required to kill all organisms present
increases with population size or density.

8. • In this method of final death rate of microorganism is to plot
graph between survivor against time of exposure.
• It is defined as time (in minutes) required to reduce the number
of viable microorganisms by 90%. A ‘D-value’ is denoted with the
capital letter "D".
• The order of death of microorganisms can be calculated by
following eq.
K = 1/t (log No – log N)
• Where, K = Constant
t = time of exposure in minute
No = Number of viable organism in the beginning
N = Number of viable organism at the end.

9. Physical
Method
Chemical
Method
Mechanic
al Method
Sterilizatio
n Methods
Dry Heat Sterilization
Moist Heat Sterilization
Radiation Sterilization
Liquid Material
Gaseous Material
Sintered Glass Filters
Sintered Metal Filters
Membrane Filters

11. • Heat Sterilization -
• Dry Heat Sterilization. E.g.- Hot Air Oven.
• Moist Heat Sterilization. E.g.- Autoclave.
• Radiation Sterilization. E.g.- Electromagnetic Rays
• Filtration Sterilization. E.g.- Membrane, Sintered Glass.
Heat Sterilization
• It involving destruction of enzymes and other essential cell
constituents.
• This method of sterilization can be applied only to the thermo-
stable products, and this process is more effective in hydrated
state(moist).
• It can be used for moisture-sensitive materials for which dry
heat (160-180°C) sterilization is applied.
• For moisture-resistant materials for which moist heat(121-

12. Hot Air Oven-
• Dry heat sterilization is usually carried out in a hot air oven, which
consists of the following:
I. An insulated chamber surrounded by an outer case containing
electric
II. heaters.
III. A fan
IV. Shelves/trays
V. Temprature control knob
VI. Thermometer
VII. Door locking controls.

13. • Different temperature-time relations for holding time are
• 60 minutes at 160°C, 40 minutes at 170°C and
• 20 minutes at 180°C.
• Increasing temperature by 10 degrees, shortens the sterilizing time by 50
percent.
• The heat is transferred to the article by radiation, conduction and convection.
o Operation-
• (i) Articles to be sterilized are first wrapped or enclosed in containers of
cardboard, paper or aluminium.
• (ii) Then, the materials are arranged to ensure uninterrupted air flow.
• (iii) Oven may be pre-heated for materials with poor heat conductivity.
• (iv) The temperature is allowed to fall to 40°C, prior to removal of sterilized

14. o Precautions- Glass materials must be wrapped with clean
cloth or filter papers and should not be placed at the floor of
the oven as it receives direct heat.
o Advantages- It is used for sterilisation of oily & powders
materials and suitable for equipment's such as glass-wares,
syringes.
o Disadvantages- It is not suitable for plastic, rubber goods
because those materials exposed to a very high temperature
for a long time.
• This method is not suitable for surgical dressings.

15. • Moist heat may be used in three forms to acts by coagulation
and denaturation of proteins and to achieve microbial
inactivation.
• At temperature below 100°C. e.g. Pasteurization.
• At temperature 100°C. e.g. Boiling.
• At temperature above 100°C. e.g. Autoclave.
Autoclaving-
• It works on the principle of Steam Under Pressure and used
to generate high temperature needed for sterilization.
• The use of steam in the range of 121-134°C Temprature.

16. • Two type of cylinder are used. They are Horizontal
Autoclaves and Vertical Autoclaves. The combination of
Different Temprature and atmospheric pressure are used
for destroy the micro- organism and sterilize the material.
o For Autoclaving, Different Sterilization Conditions
Are:
Sr. No. Temprature
(in Degree
Celsius)
Time Required
(in min.)
Pressure
(lbs/sq.inch)
1 100 ℃ 90 0
2 110 ℃ 60 5
3 116 ℃ 30-40 10
4 121 ℃ 15-20 15
5 126 ℃ 10 20
6 135 ℃ 3 30

17. o Operation-
• Ensure that there should be sufficient water in the autoclave to
produce the steam.
• When water started boils, atmospheric pressure also increases, but if
pressure is raised, the temperature at which the water boils also
increases.
• The steam pressure starts raising & it comes to the desired pressure
i.e. 15 lbs/sq.inch with corresponding temperature 121°C and it will
take 15-20 minute. Allow to cool to about 40℃ before opening the
vent.
• The stages of operation of autoclaves include air removal, steam
admission and sterilization cycle includes:
• heating up,
• holding/exposure, and

18. o Advantages- It is used for sterilisation of surgical
dressings & surgical instruments. & It has more
penetrative power than dry air.
o Disadvantages- Drenching and wetting or articles may
occur, not suitable for powders & oils., takes long time to
cool.
Fig. Vertical Autoclave Fig. Horizontal Autoclave

19. • The major target of Radiations sterilization is microbial DNA.
• Two types of radiation are used:-
I. Ionizing. e.g. X-rays, Gamma.
II. Non-Ionizing. e.g. Infra-red, Ultraviolet.
o Ionizing rays (Cold sterilization) are high-energy rays with good penetrative
power.
• It employed to sterilize articles like syringes, glass- wares, fabrics gloves,
dressing packs, foods and pharmaceuticals.
o Non-ionizing rays (Hot sterilization) are low energy rays with poor
penetrative power. It control closed environment with UV lamp.
• It employed to disinfect hospital wards, operation theatres, virus laboratories,
corridors.

20. • Filtration process does not destroy but removes the micro-organisms. It is used
for both the clarification and sterilization of liquids and gases.
• It used to remove particles from solutions that can't be autoclaved and used to
remove microbes from heat labile liquids such as serum, antibiotic solutions,
sugar solutions etc.
o Different types of filters are:
1) Earthenware filters
2) Asbestos filters
3) Sintered glass filters
4) Membrane filters (for sterility testing)
o Air Filters: Air can be filtered using HEPA (High Efficiency Particle Air) filters. It is
usually used in biological safety cabinets.
o HEPA filters are at least 99.97% efficient for removing particles >0.3 μm in

21. o Chemical agents (disinfectant) are two types:
I. Liquid
i. Alcohol (Ethyl alcohol, Isopropyl alcohol, Tri-chlorobutanol)
ii. Halogen (Iodine, Chlorine)
II. Gases
• Ethylene Oxide
• Formaldehyde
Alcohol
o Mode of action: Alcohols dehydrate cells, disrupt membranes
and cause coagulation of protein/ involved in denaturation of
bacterial proteins.
• Alcohols are mainly used as sanitizing agent (disinfecting +
antiseptic) agent and an efficient at optimum conditions.

22. Halogen
o Mode of action: They are oxidizing agents and cause
damage by oxidation of essential enzymes.
• Examples: Chlorine compounds (chlorine, bleach,
hypochlorite) and iodine compounds (tincture iodine).
Gaseous Sterilization
• Gaseous sterilization involves the process of exposing
equipment or devices to different gases in a closed
heated or pressurized chamber.
• The most common gases used for sterilization include
ethylene oxide, ozone, nitrogen and chlorine dioxides.
• The chemically reactive gases ethylene oxide and
formaldehyde posses broad spectrum biocidal activity.

23. o R. M. Mehta, A textbook of “Pharmaceutics-1”, Sixth
Edition Reprint 2018, Vallabh Prakashan, Page No.
224-252.
o www.google.com
• https://www.researchgate.net/publication/3158044
56
• www.microrao.com ‘Sterilization and Disinfection’.
o www.slideshare.com
• Mr. R.R. Patil, Sterilisation.
• Ch.Vamsi Anil Krishna, Sterilization.