Question

Describe the structure and working of a sparged stirred-tank bioreactor.

Hint:

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Answer 1

Structure of Sparged Stirred-Tank Bioreactor:

A sparged stirred-tank bioreactor is a commonly used vessel for carrying out fermentation and large-scale cultivation of microorganisms or cells. The key components of its structure include:

• Cylindrical Vessel: The main body is a vertical cylindrical tank made of stainless steel, often jacketed for temperature control.
• Agitator (Impeller): A motor-driven shaft with blades inside the tank helps in mixing the contents to ensure uniform distribution of nutrients and cells.
• Sparger: A gas-inlet device at the bottom of the tank that introduces sterile air or gases (like oxygen) in the form of fine bubbles into the culture medium.
• Baffles: Vertical plates attached to the inner walls to reduce vortex formation and improve mixing efficiency.
• Ports and Sensors: Multiple ports for inoculation, sampling, pH and temperature sensors, nutrient addition, and harvesting.
• Control System: Automated controls for parameters like pH, temperature, aeration rate, and agitation speed.

Working of Sparged Stirred-Tank Bioreactor:

The working of the bioreactor involves the following steps:

1. Sterilization: The bioreactor is first sterilized to prevent contamination.
2. Inoculation: The desired microbial culture or cells are introduced into the sterile nutrient medium.
3. Agitation: The impeller continuously stirs the medium to keep the cells in suspension, distribute nutrients evenly, and improve heat and mass transfer.
4. Aeration: The sparger injects air or oxygen into the culture. The bubbles rise and dissolve in the liquid, providing the oxygen needed for aerobic metabolism.
5. Monitoring and Control: pH, temperature, and dissolved oxygen are constantly monitored and controlled using feedback systems to maintain optimal growth conditions.
6. Product Harvesting: After sufficient biomass or product accumulation, the contents are harvested for downstream processing.

Advantages:

• Efficient oxygen transfer due to sparging and stirring
• Uniform mixing ensures consistent environmental conditions for cells
• Scalable and suitable for industrial production of biomolecules

Conclusion:

The sparged stirred-tank bioreactor is an essential tool in biotechnology and industrial microbiology for culturing cells under controlled conditions, especially for the production of pharmaceuticals, enzymes, and other biologically important products.