Small volume cultures cannot give large quantities of the products. To
product large quantities of these products development of "bioreactors"
was required where large volumes (100−1000 litres) of culture can
be processed. Hence bioreactors are like vessels in which raw materials
are biologically converted into specific products, individual enzymes or
using microbial, plant, animal or human cells. A bioreactor provides
the optimal conditions for obtaining the desired product by providing
optimum growth conditions such as substrate, temperature, pH,
vitamins, oxygen and salts. One of the most commonly used bioreactor is
of stirring type.