The control of microorganisms is of greatest importance to human health as well as preservation of food, the ability to control microbial population on inanimate objects like eating utensils,also the prevention and treatment of diseases.
For instance, the water we take is very essential to our immune system, it helps in food digestion,regulate the body temperature, aids excretion. And helps in the proper flow of blood in the body system which yield in proper growth of the body system to produce sound health.
The water we take must have the standard operating procedures of (s o p) of world health organization (W.H.O) and must be well screened with the right procedures. In order to achieve a good result in the laboratory all apparatus which are to be used in the laboratory must be well sterilize .sterilization is the process by which all microorganisms present are removed or destroyed.
The inability to sterilize the apparatus or equipment been used in the laboratory for the screening will produce wrong result and not reveal to us if the water is good for drinking or not .in the laboratory all apparatus must be well sterilize by an equipment called autoclave ;boiling at 100 degree celcius for 10mins at a pressure of 103 kpa which is usually enough to achieve sterility and eliminate all the bacteria present which may cause any interference or any form of disease.
Also boiling helps to kill bacteria present in our water, this will lead us to physical methods of sterilization. They include
Sterilization by Heat
Boiling at 100 degree Celsius for 10 mins is enough to achieve sterility, provided they are not present in high concentrations, in most cases, bacteria are killed at about 70 degree celsius. However endospores of certain bacteria are present they can resist boiling, sometimes for several hours.
A typical laboratory treatment is 15 mins at a pressure of 103kpa raising the temperature of steam to 121 degree Celsius. An effect similar to that can be obtained by a method called intermittent steaming or Tyndallization. John tyndall was one of the first to carried out the existence of heat resistant microbial forms.
This is used for those substances or material that might be damage by the high temperature used in autoclaving. The material are heated between 90 and 100 degree Celsius for about 30mins on each of the three successive days and left at 37 degree Celsius in the Intervening periods. Vegetative cells are killed off during heating period. Vegetative cells are cells that do not participate in the production of gamete, they are unicellular algae that is actively growing instead of forming spore. These methods employ above are to eliminate microorganism and also prevent us from any form of diseases.
High temperatures can cause damage to the taste, texture and nutritional value of many food substances and in such instances, it is sufficient to destroy vegetative cells by a process called pasteurization. Pasteurization is the process of heat processing of a liquid or a food to kill pathogenic bacteria (and causing disease agents) it is used in milk product. It uses lower temperature to kill bacteria in milk and allow the milk product such as cheeses to retain it original taste.
Sterilization by Radiation
There are two types of sterilization by radiation, ionizing radiation and non-ionizing radiation. Ionizing radiation can be defined as the process of using short wavelength, high-intensity radiation to destroy microorganisms. This radiation can come in the form of gamma or X-rays that react with DNA resulting in a damaged cell. Non-ionizing radiation make uses of longer wavelength and lower energy. Therefore, non-ionizing radiation loses the ability to penetrate substances, and can be used only for sterilizing surfaces. The most common class of non-ionizing radiation is ultraviolet light, which is generally used in numerous ways in different industry.
One of the industrial application of non-ionizing radiation is the breaking down of ozone (O3). This is done by adding ozone to water, bacteria are unable to sustain life. Unluckily, ozone also destroys process media. As a result ozone must be broken down so that water can be used for its intended purpose. Because ozone is very sensitive to ultraviolet light, pass the water stream under UV bulbs. This breaks down the oxygen-oxygen bonds and results in safe process water.
Sterilization by Filtration
During this method, the liquids are filtered through bacterial filters to remove any microbes present. This method is an effective technique of sterilization for heat sensitive liquids. The chances of clogging and long time duration for the process are drawbacks.
There are three types of filters used for sterilization as follows:
a) Membrane filters: Membrane filters are thin filters which are made of cellulose. They can be used for online sterilization during injection by placing the membrane between the syringe and needle.
The disadvantage is there is chances of rupture of membrane leading to improper sterilization.
b) Seitz filters:These are made of asbestos or other material. They are pad like and more thicker than membrane filters. They do not rupture during filtration. But the solution might get absorbed by the filter pad itself.
Alternative type of filter is sintered glass filters. These are made of glass and hence do not absorb liquids during filtration. The disadvantage is that they are very brittle and break easily.
c) Candle filters: These are made of clay like diatomous mud. This special mud has minute pores made by algae. The filters have many minute, lengthy pores. The microbes get stuck during their travel through the pore in the candle.
All these food substance are needed in our body system to supply us the required nutrients and should have the standard of (W.H.O) for sound health and also to prevent disease