(a) Bioreactor – Bioreactors are large vessels normally 100-1000 litres which are used for biological conversion of raw materials into specific products. Each bioreactor has a cylindrical stirred tank to facilitate the mixing of contents. The stirrer provides, facility of mixing the contents as well as the availability of oxygen. A bioreactor is more advantageous than shake flasks. It has an agitator system to mix the contents properly, an oxygen delivery system to make availability of oxygen, a foam control system, a temperature control system, a pH control system and a sampling port to withdraw the small volumes of the culture periodically. ` 

(b) Downstream Processing – Once the foreign gene product is synthesised, it is collected from the bioreactor and then processed further for its separation and purification. The purified and finally finished product is now ready for marketing. After biosynthetic stage, the collection of product, its separation and purification is known as downstream processing. Before marketing, the product has to be formulated with siuitable preservatives. In case of drugs obtained from recombinant proteins, clinical trials and strict quality control testing must be carried. These quality control testings and clinical trials vary form product to product.