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The term biotechnology refers to the use of living organisms and their products to modify and improve human health and the environment. Genetically modified organisms are used to achieve the aim.

(a) Bioreactors, also known as fermenters are chambers in which microorganisms are cultured in a liquid medium. In these vessels, the raw materials are biologically converted into specific products. The development of bioreactors greatly helped in producing the desired products on a large scale. Now, large volumes (100-1000 L) f culture can be processed in a single bioreactor. These fermenters provide and regulate optimum growth conditions such as temperature, pH, substrate and salt concentration and maintain a continuous supply of oxygen.

(b) The most commonly used bioreactors are of stirring type. The structure of a stirred bioreactor is cylindrical which facilitates even mixing of raw materials and the liquid culture throughout the tank. It also ensures a continuous supply of oxygen. The reactor is provided with a baffle and a rotating stirrer that offers excellent mixing. The tank also possesses inlets/sampling ports that allows the person to alter the volumes of the culture. The tank has multiple controlling systems such as pH, temperature, foam, oxygen delivery and agitator system. A figure of a stirred-tank reactor is shown below.