cultures at all stages, from the preliminary culture to the fermentor. A fermentor can be sterilized either by destroying the microorganisms with some lethal agent such as heat, radiation, or a chemical, or by removing the viable microorganisms by a physical procedure such as filtration.
During fermentation the following points must be observed to ensure sterility:
sterility of the culture media
sterility of incoming and outgoing air
appropriate construction of the bioreactor for sterilization and for prevention of contamination during fermentation
STERILIZATION OF THE CULTURE MEDIA
Nutrient media as initially prepared contain a variety of different vegetative cells and spores, derived from the constituents of the culture medium, the water and the vessel. These must be eliminated by a suitable means before inoculation. A number of means are available for sterilization, but in practice heat is the most often used mechanism.
A number of factors influence the success of heat sterilization: the number and type of
microorganisms present, the composition of the culture medium, the pH value, and the
size of the suspended particles. Vegetative cells are rapidly eliminated at relatively low
temperatures such as 60 degrees Celcius for 5-10 minutes, but for destruction