Read the passage and answer the following questions:
In almost all recombinant technologies, the ultimate aim is to produce a desirable protein. Hence, there is a need for the recombinant DNA to be expressed. The foreign gene gets expressed under appropriate conditions. After having cloned the gene of interest and having optimised the conditions to induce the expression of the target protein, one has to consider producing it on a large scale. The cells harbouring cloned genes of interest may be grown on a small scale in the laboratory. The cultures may be used for extracting the desired protein and then purifying it by using different separation techniques. Small volume cultures cannot yield appreciable quantities of products. To produce in large quantities, the development of bioreactors, where large volumes of culture can be processed, was required. The most commonly used bioreactors are of stirring type.
With respect to a stirred-tank bioreactor, which of the following pairs is correctly matched?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Curved base of a stirred-tank reactor – facilitates the mixing of the reactor contents
Stirred-tank bioreactors are the most common type. Each part of the reactor has its own job. The tank is cylindrical or has a curved base so that its contents mix well, and each problem such as foam or pH has its own control system.
Option (1) Agitator system – breaks the foam formed in the culture — Incorrect. Foam is handled by the foam control system. The agitator system stirs and mixes the culture.
Option (2) Curved base of a stirred-tank reactor – facilitates the mixing of the reactor contents — Correct. A curved base leaves no dead corners, so the stirred contents mix evenly.
Option (3) Sampling ports – large volumes of the culture are withdrawn periodically — Incorrect. Sampling ports let small volumes of the culture be withdrawn from time to time for checking. Taking out large volumes would defeat the purpose of a large-scale culture.
Option (4) Oxygen delivery system – maintains the optimum pH of the culture — Incorrect. The oxygen delivery system supplies oxygen. The pH is kept right by a separate pH control system, which adds acid or base.
NCERT Extract:
Obtaining the Foreign Gene Product – “A stirred-tank reactor is usually cylindrical or with a curved base to facilitate the mixing of the reactor contents. The stirrer facilitates even mixing and oxygen availability throughout the bioreactor. Alternatively air can be bubbled through the reactor. If you look at the figure closely you will see that the bioreactor has an agitator system, an oxygen delivery system and a foam control system, a temperature control system, pH control system and sampling ports so that small volumes of the culture can be withdrawn periodically.”