Bioreactor- Definition, Design, Principle, Parts, Types, Applications, Limitations


Biotechnology is the application of biological systems, organisms, or processes to produce useful products or services. Biotechnology has a wide range of applications in various fields such as medicine, agriculture, food, environment, and industry. However, biotechnology often requires the use of specialized equipment and devices to manipulate and control the biological systems or processes involved. One of the most important and widely used devices in biotechnology is the bioreactor.

A bioreactor is a device that supports a biologically active environment, where biochemical reactions or biological transformations take place. A bioreactor can be a vessel, a tank, a column, a pipe, or any other container that can hold a liquid, a gas, or a solid medium with living cells or enzymes. A bioreactor can also be a system that mimics the natural conditions of a specific tissue or organ, such as a heart, a liver, or a bone.

The main purpose of a bioreactor is to provide optimal conditions for the growth and activity of the biological agents (such as microorganisms, animal cells, plant cells, or enzymes) and to facilitate the production of the desired products (such as biomass, metabolites, proteins, drugs, biofuels, or bioplastics). A bioreactor can also be used for other purposes such as waste treatment, bioremediation, biosensing, or bioartificial organs.

Depending on the type and scale of the bioprocess involved, different types of bioreactors can be used. Some of the common types of bioreactors are:

  • Continuous stirred tank reactor (CSTR): A bioreactor that operates in a continuous mode, where fresh medium is added and product is removed at a constant rate. The bioreactor is equipped with an agitator that provides mixing and aeration. CSTRs are widely used for aerobic fermentation processes such as ethanol production.
  • Airlift reactor: A bioreactor that uses air bubbles to provide mixing and aeration. The bioreactor consists of two zones: a riser zone where air is sparged and a downcomer zone where air is separated. Airlift reactors are suitable for aerobic processes involving gas-liquid or gas-liquid-solid systems such as algal cultivation.
  • Bubble column reactor: A bioreactor that consists of a cylindrical vessel with a gas sparger at the bottom. The gas bubbles rise through the liquid medium and provide mixing and mass transfer. Bubble column reactors are simple and low-cost devices that can be used for aerobic processes such as wastewater treatment.
  • Fluidized bed reactor: A bioreactor that uses small particles as carriers for immobilized cells or enzymes. The particles are fluidized by an upward flow of liquid or gas and form a dense bed with good mass transfer and mixing characteristics. Fluidized bed reactors are used for high-rate anaerobic processes such as methane production.
  • Packed bed reactor: A bioreactor that uses solid particles as carriers for immobilized cells or enzymes. The particles are packed in a fixed bed and the liquid or gas flows through the interstices. Packed bed reactors have high surface area and low pressure drop but may suffer from clogging and channeling problems. Packed bed reactors are used for low-rate anaerobic processes such as hydrogen production.
  • Photobioreactor: A bioreactor that uses light as an energy source for photosynthetic organisms such as microalgae or cyanobacteria. The bioreactor can be illuminated by natural sunlight or artificial light sources. Photobioreactors can be designed in various shapes and configurations such as tubular, flat panel, helical, or vertical. Photobioreactors are used for the production of high-value products such as pigments, antioxidants, or biofuels.
  • Membrane bioreactor: A bioreactor that combines conventional biological treatment with membrane filtration. The membrane acts as a physical barrier that retains the biomass and separates the product from the medium. Membrane bioreactors can achieve high-quality effluent and high biomass concentration but may require frequent cleaning and maintenance. Membrane bioreactors are used for wastewater treatment and water reuse.

Bioreactors are essential tools for modern biotechnology as they enable the efficient and controlled conversion of raw materials into valuable products by biological means. Bioreactors also offer opportunities for innovation and discovery in various fields of science and engineering. By understanding the principles and design of bioreactors, one can harness the potential of biological systems for various applications.