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Stirred tank reactors (STR) are bioreactors designed to cultivate cells or microorganisms that are not susceptible to damage by shear forces.

A STR design implies that these reactors are mechanically agitated. On the contrary, the agitation in bubble columns and airlift bioreactors is produced by the air (or another gas) inlet to the system.

STR consists of a vessel with propellers (of very diverse kinds) mechanically moved by an external motor, allowing the homogeneity of the bioreactor.

A perfusion reactor or a perfusion culture is a technique in which a homogenized reactor is continuously drawn out and simultaneously supplied with fresh medium. The broth is filtered, allowing the cells or microorganisms to stay in the reactor. Therefore, the cell density drastically increase in the culture.

Hope I've helped.

Peter F. Stanbury, Allan Whitaker, Stephen J. Hall. Chapter 7 - Design of a fermenter, Editor(s): Peter F. Stanbury, Allan Whitaker, Stephen J. Hall. Principles of Fermentation Technology (Third Edition). Butterworth-Heinemann, 2017, pp. 401-485,

Stirred-Tank Bioreactors

They are one of the most common types of bioreactors used in biotechnology. They consist of a cylindrical vessel equipped with a stirrer or agitator to ensure proper mixing of the culture medium. This mixing is essential for uniform distribution of nutrients, oxygen, and cells throughout the reactor.

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Applications:

• Production of pharmaceuticals (Antibiotics, vaccines, enzymes, and other biomolecules).
• Biofuels: Ethanol, biodiesel, and other biofuels.
• Food and beverage industry (Fermented products like yogurt, cheese, and beer).
• Environmental applications (Wastewater treatment, bioremediation).

Perfusion Bioreactors

Perfusion, the continuous flow of fluid through a system, is essential in bioreactors. In this context, it involves a constant stream of culture medium, removing waste and providing fresh nutrients. This maintains a stable environment for cell growth and product production. Perfusion bioreactors, a type of continuous culture system, leverage this principle. By continuously adding fresh medium and removing spent medium, they achieve high cell densities and continuous product output, making them ideal for large-scale bioprocesses.

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Advantages:

High cell densities: Can achieve much higher cell densities compared to batch or fed-batch cultures.

Continuous production: Allows for continuous production of products without the need for frequent batch cycles.

Improved product quality: Can often result in higher product yields and quality.

Reduced downtime: Minimizes downtime associated with batch processing.

Applications:

• Used extensively in the pharmaceutical industry for the production of monoclonal antibodies.
• Suitable for the production of recombinant proteins in large quantities.
• Used for the production of cells for cell therapy applications.