Sterilization (microbiology)
Sterilization (British English: sterilisation) refers to any process that removes, kills, or deactivates all forms of life (particularly microorganisms such as fungi, bacteria, spores, and unicellular eukaryotic organisms) and other biological agents (such as prions or viruses) present in or on a specific surface, object, or fluid.[1] Sterilization can be achieved through various means, including heat, chemicals, irradiation, high pressure, and filtration. Sterilization is distinct from disinfection, sanitization, and pasteurization, in that those methods reduce rather than eliminate all forms of life and biological agents present. After sterilization, an object is referred to as being sterile or aseptic.
For other uses, see Sterilization (disambiguation).Applications[edit]
Foods[edit]
One of the first steps toward modernized sterilization was made by Nicolas Appert, who discovered that application of heat over a suitable period slowed the decay of foods and various liquids, preserving them for safe consumption for a longer time than was typical. Canning of foods is an extension of the same principle and has helped to reduce food borne illness ("food poisoning"). Other methods of sterilizing foods include ultra-high temperature processing (which uses a shorter duration of heating), food irradiation[2][3] and high pressure (pascalization).[4]
In the context of food, sterility typically refers to commercial sterility, "the absence of microorganisms capable of growing in the food at normal non-refrigerated conditions at which the food is likely to be held during distribution and storage" according to the Codex Allimentarius.[5]
Sterile filtration[edit]
Fluids that would be damaged by heat, irradiation or chemical sterilization, such as drug solution, can be sterilized by microfiltration using membrane filters. This method is commonly used for heat labile pharmaceuticals and protein solutions in medicinal drug processing. A microfilter with pore size of usually 0.22 μm will effectively remove microorganisms.[65] Some staphylococcal species have, however, been shown to be flexible enough to pass through 0.22 μm filters.[66] In the processing of biologics, viruses must be removed or inactivated, requiring the use of nanofilters with a smaller pore size (20–50 nm). Smaller pore sizes lower the flow rate, so in order to achieve higher total throughput or to avoid premature blockage, pre-filters might be used to protect small pore membrane filters. Tangential flow filtration (TFF) and alternating tangential flow (ATF) systems also reduce particulate accumulation and blockage.
Membrane filters used in production processes are commonly made from materials such as mixed cellulose ester or polyethersulfone (PES). The filtration equipment and the filters themselves may be purchased as pre-sterilized disposable units in sealed packaging or must be sterilized by the user, generally by autoclaving at a temperature that does not damage the fragile filter membranes. To ensure proper functioning of the filter, the membrane filters are integrity tested post-use and sometimes before use. The nondestructive integrity test assures the filter is undamaged and is a regulatory requirement.[67] Typically, terminal pharmaceutical sterile filtration is performed inside of a cleanroom to prevent contamination.