Question

Choose the statements that are correct with respect to continuous culture systems:
(A) In a simple stirred tank bioreactor, stirring happens through sparging of air bubbles
(B) A bioreactor has an agitator system, oxygen delivery system, and foam control system
(C) Sampling ports provide vents to withdraw small volumes of culture periodically
(D) Culturing in bioreactors is classified as downstream processing
Choose the correct answer from the options given below:

• A. (A), (B) and (C) only
• B. (A), (C) and (D) only
• C. (B) and (C) only
• D. (A) and (D) only

Answer 1

The Correct Option is A

Let's evaluate each statement in the context of continuous culture systems: 

1. (A) In a simple stirred tank bioreactor, stirring happens through sparging of air bubbles: This is true. In stirred tank bioreactors, sparging air bubbles can facilitate mixing and oxygen transfer.
2. (B) A bioreactor has an agitator system, oxygen delivery system, and foam control system: This is accurate. Most bioreactors include these components to maintain optimal conditions for microbial growth and product formation.
3. (C) Sampling ports provide vents to withdraw small volumes of culture periodically: Correct. Sampling ports are used to take culture samples for analysis without disturbing the entire system.
4. (D) Culturing in bioreactors is classified as downstream processing: Incorrect. Culturing in bioreactors is an upstream process, whereas downstream processing involves product purification and recovery.

Hence, the correct set of statements is: (A), (B) and (C) only.

Answer 2

Let's evaluate each statement with respect to continuous culture systems:

(A) In a simple stirred tank bioreactor, stirring happens through sparging of air bubbles: This is correct. In a stirred tank bioreactor, sparging refers to the introduction of air (or other gases) into the culture, which not only provides oxygen but also helps in stirring the culture by creating bubbles. This facilitates mixing and aeration.

(B) A bioreactor has an agitator system, oxygen delivery system, and foam control system: This is correct. Bioreactors typically have an agitator system (for mixing), an oxygen delivery system (for providing oxygen to microbes or cells), and a foam control system (to manage foam formation during fermentation or culture).

(C) Sampling ports provide vents to withdraw small volumes of culture periodically: This is correct. Sampling ports are used in bioreactors to withdraw small volumes of culture for analysis or monitoring. This is important for maintaining the desired conditions and for assessing the culture's growth.

(D) Culturing in bioreactors is classified as downstream processing: This is incorrect. Downstream processing refers to the processes that occur after the culture phase, such as harvesting, purification, and product recovery. Culturing in bioreactors is part of the upstream processing phase, which involves growing cells or microorganisms and producing the target product.

Thus, the correct answer is (1) (A), (B), and (C) only.