Sterilization and Disinfection Methods
For any microbiological culture, firstly, it is necessary to have a contamination free seed culture, and secondly, the equipment and media that are used, should be fully sterilized. In large scale installations, heat (dry or steam) is the most important means for sterilization, since vegetative cells of most micro organisms are rapidly eliminated by heating the culture. The equipment is generally sterilized at temperatures that are not very high, although for destroying spores (specially of bacteria) temperatures as high as 121°C are needed. Other sterilization techniques involve use of radiation (UV, X-rays), chemicals or mechanical removal of organisms.

In most microbiological operations, the air passing through the reactor culture vessel should also be sterilized, since outdoor air contains approximately 5 to 2000 micro-organisms m-3, with 50% of them in the form of fungal spores and 40% being gram negative bacteria. Among various methods available for sterilizing gases are filtration, gas (ozone) injection, gas scrubbing, radiation (UV) and heat. In most industrial establishments, the gas is sterile filtered by passing it through removable cartridges of filter systems, containing membranes made up of, cellulose ester, polysulfone or nylon, which can filter off most   of the microorganisms.