Describe briefly bioreactors.

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.