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There are many different types of bioreactors including bubble column bioreactors, continuous stirred tank bioreactors, fluidized bed bioreactors, packed bed bioreactors, and photobioreactors. The most common bioreactors are the stirred tank, airlift, and fixed-bed types.
Bioreactors are essential tools in biotechnology and have revolutionized research in various fields. They are most commonly used in the production of vaccines, biopharmaceuticals, and biofuels, and there are several types of bioreactors, each with its own advantages and limitations.
In this article, we will explore six types of bioreactors to understand why it is crucial to choose the most appropriate system for your particular application.
Bioreactors are specialized vessels designed for the growth and cultivation of microorganisms, plant and animal cells, and tissues. They are important tools in biotechnology, used for a variety of purposes such as the production of pharmaceuticals, vaccines, biofuels, and food products. Essentially, a bioreactor is a system that provides a controlled environment for cells or microorganisms to grow and multiply.
The design of a bioreactor is dependent on the type of organisms being cultivated and the intended use of the final product. Typically, bioreactors are equipped with sensors to monitor and control factors such as temperature, pH, oxygen, and nutrient levels. They may also have mechanical agitators or impellers to ensure that the cells or microorganisms are evenly distributed throughout the reactor.
Bioreactors come in various shapes and sizes, ranging from small benchtop units to large industrial-scale vessels. Some bioreactors are single-use, while others are designed for multiple uses, so the choice of bioreactor depends on the specific application and the level of production you require.
The bioreactor working principle is relatively simple, but the technology behind it is incredibly complex. As mentioned, essentially, a bioreactor is a vessel in which living cells or organisms are grown under controlled conditions to produce a particular product.
The first step in understanding how bioreactors work is to understand what they are made of. Typically, a bioreactor consists of a container, an agitator, and a means of controlling temperature, pH, and other environmental factors. The container can be made of glass or stainless steel and has ports for adding nutrients, removing waste, and monitoring the progress of the culture. The agitator is used to mix the contents of the bioreactor to ensure that all cells receive an equal supply of nutrients and oxygen.
The bioreactor working principle involves creating an environment that is conducive to the growth of the cells or organisms being cultured. For example, if you were trying to produce a particular protein using bacteria, you would need to provide them with the right nutrients, such as glucose and amino acids. You would also need to control the temperature and pH of the culture to ensure that the bacteria grow optimally.
Once you have set up the bioreactor with the right conditions, you would then inoculate it with the bacteria. Over time, the bacteria would multiply and produce the protein that you are interested in. As they do so, they will consume nutrients and produce waste products, such as carbon dioxide and lactic acid. These waste products can build up in the culture and affect its growth, so it is essential to remove them periodically.
One type of bioreactor that has gained popularity in recent years is the airlift bioreactor. This type of bioreactor is similar to a bubble column reactor, however, airlift bioreactors contain a draft tube. The draft tube can either be an inner tube (with an internal loop) or an external tube (with an external loop), but the functionality is the same: to improve circulation and oxygen transfer. The draft tube also equalizes shear forces into the bioreactor.
Airlift bioreactors with internal loops create interior liquid circulation channels via a single container. They are simple and have a fixed rate during fermentation processes. Airlift bioreactors with external loops circulate through separate channels.
The performance of the bioreactor relies on the pumping or injection of air/gas, and the media circulation. Airlift bioreactors are different from stirred-tank bioreactors as they do not need a heat coat or plate to control the temperature. For temperature-dependent formations, a two-stage airlift bioreactor is used.
Bubble column bioreactors consist of a tall vertical column filled with liquid, which is aerated from the bottom to create bubbles. These bubbles provide oxygen and mixing and aeration to the system, allowing for the growth and viability of microorganisms.
The design of a bubble column bioreactor is quite simple, making it an attractive option for many applications. The vessel used is typically cylindrical and the size can be adjusted based on the desired scale of production, between an aspect ratio of 4-6.
Inside the bioreactor, air or gas is added at the base of the bioreactor column via perforated plates or pipes, or microporous spargers. Perforated plates are typically preferred as they improve the bubble column bioreactor’s performance. By adding air or gas into the cylinder, it enables gaseous exchange. The flow rate of the air or gas is influenced by mixing and oxygen transfer. The products are produced using a fermentation method where the reactants are compacted using a finely dispersed catalyst.
Continuous stirred tank bioreactors, also known as CSTRs, are the most common type of bioreactor most widely used today. They have an aspect ratio, typically between 3-5. CSTRs use turbid static or chemo static principles to control the flow rate, and when under pressure, the air is added to the culture via a sparger device.
Bubbles are formed by the sparger, which are then later broken down into smaller bubbles and evenly spread throughout the medium. This process allows the creation of a homogeneous and uniform environment inside the bioreactor. This enables a bioprocess reaction.
Fluidized Bed Bioreactors (FBBRs) are similar to bubble column bioreactors however, the top position of the FBBR is expanded and the column is narrowed to reduce the fluid velocity. This is so that the solids are maintained in the reactor while the liquid can flow out.
Inefficient FBBR operations, gas is provided to create a ‘gas-liquid-solid’ fluid bed and a good suspended state. If using a FBBR, it is also important that suspended solid particles are heavy enough to prevent them from floating. The same goes for dense particles. You do not want too many dense particles otherwise they may lay at the bottom.
The good thing with FBBRs is that you can recycle the liquid. This is essential to maintain continuous contact between the biocatalysts inside the bioreactor and the reaction contents. This is a good habit for bioprocessing, and it is important for good efficiency.
Packed bed bioreactors contain a confined bed of solid particles with biocatalysts. These solids can either consist of porous or non-porous (rigid) gels. The biocatalyst is immobilized on the solids and a medium (typically called a nutrient broth) flows constantly over it, either upward or downward. When the fluid runs upward, the velocity must not exceed the minimum fluidization velocity, which is why gravitational downward flow is preferred.
The products and metabolites inside the bioreactor are dispersed into the media fluid and during the outflow, they are removed.
Photobioreactors are a relatively new technology that has revolutionized the way we think about sustainable energy. These bioreactors are an innovative reactor that uses photosynthetic organisms to convert sunlight into usable energy, which can then be harvested and used to power a variety of different applications. Unlike traditional bioreactors which rely on chemical reactions to produce energy, photobioreactors rely solely on the power of the sun, making them incredibly eco-friendly and efficient.
The most common use is to cultivate microalgae in wastewater treatment facilities (WWTPs). The photobioreactor usually has a light source like an LED or fluorescent bulb to allow enough light for photosynthesis and a culture media. The light intensity and spectrum can be adjusted to the maximize growth of the microorganisms.
Photobioreactors may also use a mechanical stirrer or bubbling mechanism to mix the culture medium and allow air through the medium. During use, the temperature, and the pH of the culture medium must be carefully controlled accordingly to the microorganism growth. The photobioreactor being used must also be designed to prevent possible contamination.
The specific design used depends on the specific microorganism being cultivated and the final product, and there are four basic types of photobioreactors to select from:
Bioreactors are essential tools in biotechnology, providing a controlled environment for the growth and cultivation of cells and microorganisms. These specialized vessels play a crucial role in the production of a wide range of products, from pharmaceuticals to biofuels.
If you are unsure which bioreactor is best suited, do not hesitate to contact the world-class team at Atlas Scientific.
During the first stages of fermentation, kombucha requires oxygen to allow the symbiotic culture of bacteria and yeast (SCOBY) to consume sugars and excrete alcohol and CO2. During this time, the kombucha needs to be well-ventilated with oxygen. However, during the second fermentation stage, the kombucha develops its carbonation and is kept away from oxygen.
The first step in setting up a bioreactor is to choose the appropriate type of bioreactor for your application, followed by preparing the culture media. Then sterilization of the bioreactor components is required. After sterilization, the bioreactor is assembled according to the manufacturer’s instructions and the type of bioreactor. Lastly, various parameters such as temperature,
