Statement I: A stirred-tank bioreactor is usually cylindrical or has a curved base to facilitate the mixing of the reactor contents.
Statement II: In a stirred-tank bioreactor, the stirrer is used mainly to keep the culture at the optimum temperature.
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Only statement I is correct.
The most common bioreactors are of the stirring type. A stirred-tank bioreactor is a vessel with a stirrer (impeller) turned by a motor. The stirrer keeps the cells, the nutrients and the oxygen evenly spread through the culture.
Statement I: A stirred-tank bioreactor is usually cylindrical or has a curved base to facilitate the mixing of the reactor contents. — True. A round vessel has no corners where the culture could stay still, so the contents mix well.
Statement II: In a stirred-tank bioreactor, the stirrer is used mainly to keep the culture at the optimum temperature. — False. The stirrer is for even mixing and oxygen availability. Temperature is kept right by a separate temperature control system.
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system, a temperature control system, pH control system and sampling ports so that small volumes of the culture can be withdrawn periodically.”
Figure 9.7 (a) Simple stirred-tank bioreactor; (b) Sparged stirred-tank bioreactor through which sterile air bubbles are sparged