Sterilization
It is a process of removal of contaminants from a surface or a substance.
Sterilization should be proper with a single step. It will be more effective in a closed
system. Most fermenters are of open type. In them initial sterilization is done in a
system to keep them sterile throughout by ensuring the removal of any contaminant
at the entry or exit point.
Common contaminants in fermentation industry
1. In the canning industry Clostridium botulinum produces heat resistant spores
and deadly toxic compounds in sealed cans.
2. Lactobacillus is main contaminants in wine industry.
3. Mould, yeast and certain bacteria are the potential contaminants in antibiotic
industry.
4. Dreadful contaminants in fermentation industry are phage. The only solution is
to use phage resistant strains.
Sterilization methods can be broadly divided into physical and chemical.
Physical methods
1. Heating
It is the most common method of sterilization. It includes moist heat and dry
heat sterilization.
i. Moist heat is achieved by pressure cooker and autoclave. Autoclave is the
most common method in Sterilization. It is durable jacket steam chamber
equipment with the devices which permit the chamber to be filled with
saturated steam and maintain a particular temperature and pressure. Air
should be completely removed from the Chamber or else it reduces the
temperature obtained within the Chamber. Organisms are killed by the
temperature of the steam and not by the pressure. Several media solution,
discarded culture etc. are continuously sterilized with this equipment.
, Generally the autoclave is operational at a pressure of 15 LBS per square
inches at 1200C for 15 minutes.
ii. Dry heat is achieved by hot air oven. a holding period of 1500C for 2 hours is
used for sterilizing glass wares, swabs, certain pharmaceutical products like
liquid paraffin, sulphonamides etc. Hot air is a bad conductor of heat and has
low penetrating power than moist air. Oven is heated by electricity which
heats the heating coil within the Chamber the heat produced is distributed
uniformly using a fan fitted in the chamber. The material should be arranged
so that free circulation of air is possible. The materials should be perfectly
dried before placing in oven. The oven must be allowed to cool slowly for 1
hour before the door is opened or else the glass wares get broken.
2. Filtration
It is a technique of sterilization usually used for sterilization of heat labile
compounds. Aerobic fermentation requires high rates of air supply which is
free from contaminants like fungal spores or bacteria. They are usually
removed by filtration through depth filters and screen filters.
i. Depth filters: They are made of processing fibres or powdered material to
form thick layers. Cellulose, fibres, cotton, mineral, wool etc. are used to form
filters. Modern filters are made up of Boron silicate microfibers. They are
more effective than screen filters.
It is a process of removal of contaminants from a surface or a substance.
Sterilization should be proper with a single step. It will be more effective in a closed
system. Most fermenters are of open type. In them initial sterilization is done in a
system to keep them sterile throughout by ensuring the removal of any contaminant
at the entry or exit point.
Common contaminants in fermentation industry
1. In the canning industry Clostridium botulinum produces heat resistant spores
and deadly toxic compounds in sealed cans.
2. Lactobacillus is main contaminants in wine industry.
3. Mould, yeast and certain bacteria are the potential contaminants in antibiotic
industry.
4. Dreadful contaminants in fermentation industry are phage. The only solution is
to use phage resistant strains.
Sterilization methods can be broadly divided into physical and chemical.
Physical methods
1. Heating
It is the most common method of sterilization. It includes moist heat and dry
heat sterilization.
i. Moist heat is achieved by pressure cooker and autoclave. Autoclave is the
most common method in Sterilization. It is durable jacket steam chamber
equipment with the devices which permit the chamber to be filled with
saturated steam and maintain a particular temperature and pressure. Air
should be completely removed from the Chamber or else it reduces the
temperature obtained within the Chamber. Organisms are killed by the
temperature of the steam and not by the pressure. Several media solution,
discarded culture etc. are continuously sterilized with this equipment.
, Generally the autoclave is operational at a pressure of 15 LBS per square
inches at 1200C for 15 minutes.
ii. Dry heat is achieved by hot air oven. a holding period of 1500C for 2 hours is
used for sterilizing glass wares, swabs, certain pharmaceutical products like
liquid paraffin, sulphonamides etc. Hot air is a bad conductor of heat and has
low penetrating power than moist air. Oven is heated by electricity which
heats the heating coil within the Chamber the heat produced is distributed
uniformly using a fan fitted in the chamber. The material should be arranged
so that free circulation of air is possible. The materials should be perfectly
dried before placing in oven. The oven must be allowed to cool slowly for 1
hour before the door is opened or else the glass wares get broken.
2. Filtration
It is a technique of sterilization usually used for sterilization of heat labile
compounds. Aerobic fermentation requires high rates of air supply which is
free from contaminants like fungal spores or bacteria. They are usually
removed by filtration through depth filters and screen filters.
i. Depth filters: They are made of processing fibres or powdered material to
form thick layers. Cellulose, fibres, cotton, mineral, wool etc. are used to form
filters. Modern filters are made up of Boron silicate microfibers. They are
more effective than screen filters.
