​​What Is A Bioreactor And What Is It Used For?


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A bioreactor is a device or system that provides an optimal and controlled environment for biological and chemical reactions. 

A bioreactor is a vessel or system that typically involves the growth and maintenance of microorganisms, mammalian, plant and stem cells, tissues, and algae. 

Bioreactors have revolutionized various industries, including biotechnology, pharmaceuticals, food production, and wastewater treatment. They offer significant advantages in terms of cost-effectiveness, efficiency, and precise control of growth conditions.

What Are Bioreactors Used For?

Bioreactors are an absolute game changer in a wide range of fields and industries. From pharmaceuticals to food processing, bioreactors have an incredibly diverse range of applications that have advanced the way we approach a variety of processes. Whether you’re looking to grow cells or microorganisms, or produce biofuels or chemicals, bioreactors are the go-to tool for researchers and industry professionals alike.

One of the most common bioreactor applications is in the field of pharmaceuticals. Bioreactors are used to culture cells and microorganisms that are then used to produce a wide range of drugs and medications, or even vaccines. The ability to control and monitor the environment within a bioreactor allows for more consistent and reliable production of these medications, leading to greater efficiency and ultimately lower costs.

But it’s not just the pharmaceutical industry that’s benefiting from the use of bioreactors. Bioreactors are also being used in food processing, specifically in the production of fermented foods such as yogurt, cheese, and beer. The controlled environment within a bioreactor allows for precise control over the fermentation process, leading to higher-quality products that are both more consistent and flavorful.

In addition to these more traditional applications, bioreactors are also being used in cutting-edge research around biofuels and biomaterials. By using bioreactors to culture microorganisms that can produce biofuels or other useful materials, researchers can develop sustainable alternatives to traditional fossil fuels and materials. This has the potential to not only reduce our reliance on non-renewable resources but also to mitigate some of the negative environmental impacts associated with their use.

Advantages of Using Bioreactors

There are several advantages to using bioreactors for microbial and cell culture production:

  • They are cost-effective
  • They require less manual labor, reducing operational costs
  • They are highly efficient and provide a high level of productivity, typically resulting in high yields and rapid production
  • They provide precise control and monitoring, including pH, temperature, oxygen, and nutrient supply

However, there are also some disadvantages to bioreactors:

  • They can be expensive to operate, resulting in high capital costs compared to traditional methods
  • They must be sterilized properly to prevent contamination which is expensive and time-consuming
  • They are complex systems therefore a skilled operator is required
  • For any maintenance, highly-skilled maintenance personnel is needed
  • They can have slower production methods than traditional processes

What is the Difference Between a Bioreactor and Fermentor?

Although the terms “bioreactor” and “fermentor” are often used interchangeably, there is a distinct difference between the two. A bioreactor typically refers to a device used for cultivating mammalian, plant, and stem cells, while a fermentor is specifically used for cultivating bacteria, yeast, and fungi. Bioreactors and fermentors share many similarities in terms of design and function, but their specific applications and cultivation requirements can vary depending on the type of organism being grown.

How Does A Bioreactor Work?

By providing a controlled environment, a bioreactor allows living organisms to grow, reproduce, and perform metabolic processes. This controlled environment is achieved through the regulation of various factors, including temperature, pH, oxygen concentration, and nutrient supply.

Bioreactor systems can be highly automated, using computerized processing systems to control environmental conditions, or they can be manually controlled. 

Bioreactor Components

The specific design and application of the bioreactor will determine its exact components. However, there are some standard elements found in most types of bioreactors.

The main framework is known as the fermenter vessel. It’s the part that holds nutrients and biological material. The fermenter vessel is usually made from stainless steel or glass.

The thermal jacket is the outer layer that surrounds the inside of the bioreactor chamber. This is where biological reactions take place. Similar to the fermenter vessel, the thermal jacket is typically made from stainless steel. A cooling or heating fluid (like water) is found inside the thermal jacket to regulate and control the culture’s temperature.

Bioreactors require a component to mix and distribute the biological material and nutrients, and this is where the agitation system comes in. The agitation system has a motor that turns impellers or another mixing element.

Within the vessel are vertical plates/structures called baffles. Baffles prevent vortex formation or swirling within the liquid during the agitation process. This is important in reducing microbial colonies growing on the fermenter vessel walls. Baffles can also improve the flow of the culture medium and prevent sheer stress that could be harmful to microorganisms or cells.

Oxygen is supplied to the biological material via an oxygen delivery system, also known as an aeration system. The aeration system has a sparger that delivers sterile air.

Foam is a normal occurrence in bioreactors. To prevent the buildup of extra foam in the bioreactor vessel, a foam control system is in place. Excess foam in the vessel can cause overflow which not only contaminates the surroundings, but too much foam can also damage the bioreactor vessel.

The temperature inside the bioreactor vessel is controlled and regulated via a temperature control system.

Maintaining a specific pH is also important. The pH control system has sensors that monitor the pH level. The control system can also adjust the amount of acidic or alkaline buffer added to the bioreactor. 

Sampling ports allow an entry point to the medium for easy monitoring and analysis.

Feed ports introduce additional materials the bioreactor needs for the bioprocess. The feed ports typically have sterile filters to sustain a sterile and controlled environment. 

Finally, a cleaning/sterilizing system is used to clean the bioreactor. Depending on the type of bioreactor you are using, the system can either use heat, steam, or chemical sterilization methods.

How To Set Up A Bioreactor?

The first step in setting up a bioreactor is to choose the type of bioreactor that best suits your application. Next, you need to prepare the culture media, followed by sterilization of the bioreactor components.

Once you have sterilized the bioreactor, it is assembled according to the manufacturer’s guidelines. 

During the bioreactor process various parameters, including temperature, pH, dissolved oxygen, and partial pressure of oxygen (pO2) are controlled and monitored. 

Considerations in Bioreactor Design

There are some key factors to optimize the performance of your bioreactor. 

Oxygenation for Aerobic Microorganisms

One of the critical factors to consider in bioreactor design is the method of oxygenation, particularly for aerobic microorganisms that require oxygen for their metabolic processes. Efficient oxygen transfer is essential for maintaining the growth and productivity of these organisms.

Oxygen Transfer Methods

There are several ways to transfer oxygen to the culture medium in a bioreactor:

Direct sparging: Air or oxygen is bubbled directly into the medium through a sparger or diffuser.

Surface aeration: Oxygen is transferred to the medium at the air-liquid interface through agitation or mixing.

Membrane aeration: Oxygen is supplied through a gas-permeable membrane (membraneaerated biofilm reactor) immersed in the medium. These offer a low-energy delivery of oxygen to the medium. 

The choice of oxygen transfer method depends on the specific requirements of the application and the type of bioreactor being used.

Factors Influencing Oxygen Transfer

Several factors can influence the efficiency of oxygen transfer in a bioreactor, including:

Agitation speed: Faster agitation rates generally result in higher oxygen transfer rates, but excessive agitation can cause damage to sensitive cells or microorganisms.

Gas flow rate: Higher gas flow rates can improve oxygen transfer, but this can also lead to excessive foaming and increased energy consumption.

Bubble size: Smaller bubbles have a larger surface area and offer better oxygen transfer efficiency than larger bubbles. However, smaller bubbles can also cause foaming and may be more challenging to generate and maintain.

Medium viscosity: Higher viscosity media can reduce oxygen transfer rates, making it essential to consider the impact of medium properties on oxygenation.

Temperature Management

Temperature control is another crucial factor in bioreactor design, as it can significantly impact the growth and metabolism of the microorganisms or cells being cultured. Different organisms have specific temperature requirements for optimal growth, and maintaining a stable temperature within the bioreactor is essential for successful cultivation.

Temperature Control Methods

There are several ways to control the temperature within a bioreactor:

Heating or cooling jackets: A jacket surrounding the bioreactor vessel can contain heating or cooling fluids to regulate the temperature.

Internal heat exchangers: Coils or other heat exchange devices can be immersed in the culture medium to control temperature.

Direct heating or cooling: Electrical heaters or cooling elements can be placed directly in the bioreactor to manage the temperature.

The choice of temperature control method depends on the specific application and the type of bioreactor being used.

Factors Influencing Temperature Control

Several factors can influence the efficiency of temperature control in a bioreactor, including:

Heat generation: Microbial metabolism can generate heat, which may require additional cooling measures within the bioreactor.

Heat loss: Heat can be lost from the bioreactor through conduction, convection, and radiation, which needs to be accounted for in the temperature control strategy.

Temperature gradients: Temperature gradients can develop within the bioreactor, leading to uneven growth and metabolism. Efficient mixing and agitation can help minimize temperature gradients.

Methods for Monitoring the Culture

Monitoring the culture within the bioreactor is essential for ensuring optimal growth conditions and maintaining product quality. Various methods can be used to monitor different aspects of the culture, including cell density, nutrient levels, pH, and dissolved oxygen.

Photo courtesy of Eppendorf SE

Cell Density Measurement

Cell density can be measured using several techniques, such as:

Optical density: A spectrophotometer measures the amount of light absorbed by the culture at a specific wavelength, which is proportional to the cell density.

Viable cell counting: Cells can be counted using a hemocytometer or automated cell counter after staining with a viability dye.

Biomass measurement: The total mass of cells in the culture can be determined by filtering the culture and measuring the dry weight of the collected biomass.

Nutrient Monitoring

Nutrient levels in the bioreactor can be monitored using analytical techniques such as:

HPLC (high-performance liquid chromatography): Separates and quantifies individual components in the culture medium.

Spectrophotometry: Measures the absorbance of specific wavelengths of light by the culture medium to determine nutrient concentrations.

Ion-selective electrodes: Electrodes that respond selectively to specific ions in the culture medium, such as ammonium or nitrate.

pH and Dissolved Oxygen Monitoring

pH and dissolved oxygen levels can be monitored using sensors placed within the bioreactor. These sensors typically provide real-time measurements and can be connected to a control system to maintain the desired setpoints.


Maintaining sterility within the bioreactor is crucial for preventing contamination and ensuring product quality. Several strategies can be employed to maintain a sterile environment within the bioreactor:

Sterilization of the bioreactor and its components: Bioreactors and their components can be sterilized using steam, heat, or chemical methods.

Aseptic operation: Bioreactors can be operated under aseptic conditions, with sterile air or gases used for sparging and all inputs and outputs filtered to prevent contamination.

Single-use bioreactors: Disposable bioreactors eliminate the need for cleaning and sterilization between runs and reduce the risk of contamination.

Sterilization Methods

There are several methods for sterilizing bioreactors and their components:

Steam sterilization (autoclaving): High-pressure steam is used to sterilize bioreactors and their components at temperatures of 121°C or higher.

Dry heat sterilization: Bioreactors and components are heated in an oven at temperatures of 160°C or higher for a specific period.

Chemical sterilization: Bioreactors and components are exposed to chemical sterilants, such as hydrogen peroxide or ethylene oxide, to kill microorganisms.

The choice of sterilization method depends on the specific application and the materials used in the bioreactor and its components.

Mixing and Agitation

Efficient mixing and agitation within the bioreactor are essential for maintaining uniform growth conditions, promoting mass transfer, and preventing the formation of gradients within the culture medium. There are several factors to consider when designing the mixing and agitation system for a bioreactor:

Impeller type: Various impeller designs, such as Rushton turbines, pitched-blade impellers, or marine propellers, can be used to provide the desired level of mixing and agitation within the bioreactor.

Impeller speed: The speed of the impeller can be varied to achieve the desired level of mixing and agitation, with higher speeds typically resulting in better mixing but also higher shear forces that can be detrimental to sensitive cells or microorganisms.

Baffles: Baffles can be added to the bioreactor to increase turbulence and improve mixing.

Shear Sensitivity

Some microorganisms and cells, such as mammalian cells or shear-sensitive bacteria, can be damaged by excessive shear forces generated by mixing and agitation. In such cases, it is essential to design the mixing and agitation system to minimize shear forces while still providing adequate mixing and mass transfer.

Scale-up Considerations

When scaling up a bioreactor from a laboratory-scale system to a larger production-scale system, it is essential to maintain similar mixing and agitation conditions to ensure consistent growth and productivity. Factors such as impeller type, speed, and spacing, as well as the presence of baffles, should be considered when scaling up a bioreactor.

Bioreactor Materials

The choice of materials for constructing a bioreactor is essential for ensuring the durability, reliability, and sterility of the system. Some common materials used for bioreactor construction include:

Stainless steel: Widely used for large-scale bioreactors due to its durability, corrosion resistance, and compatibility with steam sterilization.

Glass: Commonly used for smaller-scale bioreactors due to its transparency, chemical resistance, and compatibility with steam sterilization.

Polymers and plastics: Used for disposable, single-use bioreactors and components, offering advantages in terms of cost, sterility, and disposal.

The choice of material depends on the specific application, the scale of the bioreactor, and the sterilization requirements.

Bioreactor Control Systems

Bioreactor control systems are essential for maintaining optimal growth conditions within the bioreactor and ensuring the quality and consistency of the product. These systems can be either manual or automated, depending on the level of control required and the complexity of the bioreactor system.

Types of Control Systems

Several types of control systems can be used for bioreactors:

Manual control: Operators manually adjust the bioreactor parameters, such as temperature, pH, and dissolved oxygen, based on measurements taken from the system.

PID (proportional-integral-derivative) control: An automated control system that uses feedback from sensors within the bioreactor to maintain the desired setpoints for temperature, pH, and dissolved oxygen.

Advanced control systems: More sophisticated control systems that use algorithms, models, or artificial intelligence to optimize the growth conditions within the bioreactor and adapt to changes in the culture or process.

Integration with Process Monitoring and Data Acquisition

Bioreactor control systems can be integrated with process monitoring and data acquisition systems to provide real-time feedback on the performance of the bioreactor and enable more precise control of growth conditions. This can help improve the efficiency, productivity, and quality of the bioprocess.

Bioreactor SCADA Software

The term ‘SCADA’ stands for Supervisory Control And Data Acquisition. It refers to a system that allows operators to remotely monitor and control various processes and equipment in a facility. The Bioreactor SCADA software is designed to provide real-time data on the bioreactor’s temperature, pH levels, nutrient levels, and other critical parameters. This information is essential for maintaining the optimal conditions for the growth and development of the microorganisms or cells in the bioreactor.

The Bioreactor SCADA software is a sophisticated system that uses a combination of hardware and software components. The hardware components include sensors that are used to measure the various parameters. These sensors are connected to a central control system that is responsible for collecting and processing the data. The software components include the user interface, which provides operators with an intuitive interface for monitoring and controlling the bioreactor.

One of the key benefits of using Bioreactor SCADA software is that it allows for greater process control and automation. This means that operators can remotely monitor and control the bioreactor from a central location, reducing the need for manual intervention. This can lead to significant improvements in process efficiency and reduced variability in product quality. In addition, the software can be configured to provide alerts when certain parameters fall outside of predefined limits. This enables operators to take corrective action before any damage is done to the bioreactor or the microorganisms or cells being grown within it.

Types Of Bioreactors

There are several types of bioreactors, each with their specific uses and benefits. Some common types include:


These are specialized bioreactors that cultivate photosynthetic microorganisms by providing artificial light conditions. This type of bioreactor offers precise temperature, pH, and light intensity control, and results in better growth rates and cleaner samples compared to algae, moss, and other photosynthetic microorganisms growing in natural environments. 

Although closed systems are preferred as they have greater protection against contaminants and control of the environment, photobioreactors can have open or closed systems. 

Photobioreactors are not like traditional bioreactors as they solely rely on the power of the sun, which makes them a more eco-friendly and efficient bioprocess method. 

Continuous-Stirred Tank Bioreactors

CSTRs, otherwise known as continuous-stirred tank bioreactors, are the most popular bioreactors in use these days. The aspect ratio for these is generally between 3-5. The turbid static or chemo static principles are employed to regulate the flow rate with the help of a sparger device. 

The sparger produces bubbles which are then broken down into smaller bubbles and dispersed throughout the medium. This even distribution of bubbles helps create a homogeneous and uniform environment within the bioreactor, allowing bioprocess reactions to take place.

Airlift Bioreactors

The airlift bioreactor is becoming more and more popular in recent years due to the way it works. It is akin to a bubble column reactor but contains a draft tube inside or outside the system. This tube is used to help circulation and oxygen transfer, as well as to equalize shear forces. Internal loop airlift bioreactors have a single container that allows liquid to circulate through an interior channel at a fixed rate. For external loop airlift bioreactors, the liquid is circulated through separate channels.

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Bubble Column Bioreactors

The bubble column bioreactor is an attractive option for many applications due to its straightforward design. The vessel is cylindrical and the height can be adjusted to meet any desired scale of production, between 4-6 in aspect ratio. Air or gas is added to the bioreactor via perforated plates or pipes, or microporous spargers, with plates typically preferred for improved performance. The flow rate of the gas is then affected by oxygen transfer and mixing. The bioreactor is used to produce products through a fermentation method, with reactants compacted using a finely dispersed catalyst.

Fluidized Bed Bioreactors (FBBRs)

FBBRs are like bubble column bioreactors, but the top part is enlarged and the column is narrowed down to reduce the flow velocity. This is to maintain the solids in the reactor while the liquid can exit. To achieve this, gas is supplied to form a ‘gas-liquid-solid’ bed and an acceptable suspended state. It is essential that the suspended particles are heavy enough to not float, and the same goes for dense particles. If there are too many dense ones, they might settle at the bottom. Fortunately, liquids can be recycled in FBBRs, which is essential to keep the biocatalysts in the bioreactor and the reaction ingredients in contact. This is an advantageous practice for bioprocessing and is necessary for good performance.

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Packed Bed Bioreactors

A packed bed bioreactor is an enclosed system of solid particles with biocatalysts. These solids are either porous or non-porous (rigid) gels. The biocatalyst is secured to the particles, and a nutrient broth perpetually circulates over them. The flow is typically directed downward due to the need to remain below the minimum fluidization velocity. The products and metabolites formed within the bioreactor are dispersed and eliminated as the fluid is drained.

Bioreactor Processes 

The choice of bioreactor process for a particular organism and application will depend on the desired objectives, with each option having its benefits and drawbacks. These techniques may include batch, fed-batch, continuous, and perfusion.

Batch Processes

For batch processing, no more nutrients are provided during the bioprocess apart from elements for control such as gases, acids, and bases that are added at the start. This process continues until the added nutrients are all consumed by the cells. These processes are useful if the experiment needs to be conducted quickly, but the biomass and product yields are restricted. Oxygen transfer and carbon source are usually the main limitations, meaning that the microorganisms only grow exponentially for a short duration.

Fed-batch Processes

Fed-batch processing stands out from batch processing in that it involves adding nutrient feeds regularly during the process. This avoids nutrient depletion and encourages cell growth, leading to increased cell density and yield. The bioreactor is first stocked with media and inoculated with cells, after which fresh nutrient feeds are provided as required throughout the activity. Fed-batch processes are the most common and direct way to reach higher cell densities and better outcomes than with batch processing.

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Perfusion Process

Using perfusion can facilitate a longer procedure than a fed-batch one, leading to a higher cell density and increased product yields. Tangential flow filtration eliminates unnecessary components and some medium is recycled. 

This process provides a constant stream of a new medium into the bioreactor to guarantee that volume is retained, consequently augmenting cell densities and product yields. But, this is not a continuous process, since the cells will continue to grow until a point of no greater cell density is reached.

Continuous Processes

With continuous processing, bioreactors are kept stocked with a continuous supply of nutrients for the cells or microorganisms growing inside. In this type of process, a new medium is constantly being added to the bioreactor while the same amount of used media is taken away. This helps the culture remain steady in terms of growth and division, leading to a steady cell or microorganism density and a more predictable product output.

Single-use And Multi-use Bioreactors

Recently, the use of so-called disposable bioreactors has become increasingly popular due to their cost-effectiveness, flexibility, and ease of use. These bioreactors consist of a bag made of multiple polymer layers, each of which serves a specific purpose in applications such as clinical manufacturing and process development.

In contrast, multi-use bioreactors, which are usually made of either stainless steel or glass, can be employed for multiple production runs and are thus more suitable for large-scale production and extended use. However, they necessitate additional sterilization and cleaning between runs, which can be time-consuming and costly.

What Is The Future Of Bioreactors?

The future of bioreactors looks promising, with new technologies and applications emerging all the time. Some areas of growth for bioreactors include:

Synthetic biology: Bioreactors can produce synthetic organisms and genetic materials, paving the way for new advances in medicine and biotechnology.

Precision fermentation: Bioreactors can produce specific compounds or molecules through precision fermentation, allowing for more targeted production of pharmaceuticals and other products.

Sustainable agriculture: Bioreactors can produce sustainable fertilizers and pesticides, reducing the environmental impact of agriculture.


Bioreactors are fascinating pieces of technology that have revolutionized the world of science and engineering.

Photo courtesy of Eppendorf SE

If you’re looking for more information on Bioreactors, please check out www.eppendorf.com/bioprocess

If you need assistance with setting up your bioreactor or what bioreactor will best suit your application needs, do not hesitate to contact the world-class team at Atlas Scientific.

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