Give the methods used for sterilization in the lab

Method 1. Boiling:
Boiling will free liquids of living cells. However, since it is not sure whether resistantspores are present or not, it is not always safe to boil.
Elevation influences boiling point. In an open container at sea level, water boils at 100°C (212°F) but as elevation increases above sea level, the boiling point decreases.

Method 2. Intermittent Heating (Arnold Sterilisation):
This method is used to sterilise thermolabile (broken down by heat) substances which can withstand a temperature upto 100°C or lower. Normally all vegetative proteins coagulate at 60°-65°C.
For this, substances like carbohydrates are placed in running steam, after water starts boiling, for 30 minute s.
The material is taken out and kept at room temperature for 24 hours. This exposure to temperature will break the dormancy and encourage spores to germinate and produce a crop of vegetative cells.
The next day the process is repeated at the same time, which will destroy the new crop of cells. Incubate for 24 hours and repeat the process for the third day. This last heating is only as a precaution.

Method 3. Autoclaving (Steam Under Pressure):
This is the most efficient and reliable method of sterilisation. The instrument, an autoclave, is similar to home pressure cookers. This works on the principle that water boils at 100°C at atmospheric pressure of 760 mm of mercury. But if this steam is built up in a closed chamber, water can be kept boiling until the temperature goes far above 100°C.
It should be made sure that the material in the autoclave is not subject to a mixture of air and steam. For this, after tightening the lid, the valve should be kept open and all the air in the autoclave should be pushed out and replaced by steam.
After 15-20 minutes, switch off the autoclave; allow the pressure to come down to zero. Do not release the pressure quickly. This will make the containers with medium blow up their tops and spill the media. After cooling (0 lbs pr) slowly open the valve allowing air to enter the vacuum in the autoclave, created by the setting of steam.
Culture media in tubes and flasks are plugged with non-absorbent cotton to allow ready access to steam. Do not use absorbent cotton.

Method 4. Dry Heat Sterilisation Indirect Heat:
Materials like glass-wares, Petri dishes pipettes, etc. since they should be dry while using, are subject to dry heat. In addition, oils and greases should be heat (dry) sterilised since steam will not penetrate such substances. Protein (of microbes) in the absence of moisture will not coagulate at 121°C. It needs temperature well above 160°C and hence the temperature is raised to 170°C (keeping 10°C margin) and maintained for at least 1- 2 hours.
Superheated steam is dry and has no condensed moisture

Method 5. Open Flame Sterilisation:
Needles, loops, forceps, etc. are sterilised by making them red hot on a Bunsen flame, cool ed in 95% ethyl alcohol and flame heated by passing it quickly over the flame to burn off the alcohol.

Method 6. Filtration:
Filtration allows for the exclusion of organisms based upon size. There are many types of filtration techniques, but when sterilizing a system membrane filtration is used.
Membrane filtration traps contaminants larger than the pore size on the surface of the membrane. If contaminants are smaller than the desired particle, decrease the membrane pore size and trap the product while passing the contaminants through the membrane. Separation of multiple
microorganisms are possible.

Method 7. Chemical Sterilisation
Volatile disinfectants like chloroform are used for sterilisation and preservation of serum for culture media.
Disinfectants of the phenol group—lysol and cresol are powerful disinfectants for disinfecting surgical instruments and discarded cultures.
Formaldehyde kills all bacteria and spores.
Ethylene oxide is a gaseous disinfectant used for sterilising materials that damage by heat, e.g. plastic and rubber.

Method 8. Pasteurisation:
This method was invented by Louis Pasteur to destroy microorganisms in wine and beer.
Now it is more popularly used in food and beverage industries. The material is subjected to 62°C for 30 minutes or exposed to 71.1°C for 15-17 seconds followed by rapid cooling to 10°C.

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Titany answered the question on September 10, 2021 at 12:34