Question

(a) How has the development of bioreactor helped in biotechnology?
(b) Name the most commonly used bioreactor and describe its working.

Answer 1

Figure 1: A simple stirred tank bioreactor

(a) Bioreactors are designed to carry out the biochemical processes which employ microorganisms like bacteria, fungi, plant cells or mammalian cells etc. for the production of biological products.

Bioreactor has helped in biotechnology in many ways like:

1. Control over temperature and pressure of the system.

2. Ease of measurement of different functions; pH, temperature, pressure etc.

3. Stirring can be done by an automatic stirrer.

4. Aerators are employed if oxygen needs to be pumped into the system.

5. Highly efficient and safe.

6. Biotechnological processes can be carried out without adulteration/ leakage of inner material into the surroundings.

7. Automated systems.

Thus, the above points add to the help provided by the development of bioreactor in the field of biotechnology.

(b) The most commonly used bioreactor is the simple stirred tank bioreactor. It is composed of a reactor and a mixer such as a stirrer, a turbine wing or a propeller. (See figure 1)

Stirred tank reactors perform the functions like; homogenization, suspension of solids, dispersion of gas-liquid mixtures, aeration of liquid and heat exchanges. These functions form the working of the bioreactor. The variables are type, size, location and the number of impellers, sparger size, and location. These functions affect the hydrodynamic properties of the reactor. The conventional fermentation is carried out in batch mode. This type of bioreactor is useful for immobilized enzymes with relatively low activity and for substrate solutions of high viscosity. The disadvantage of this bioreactor is that the immobilized enzyme tends to decompose during stirring.