A bioreactor refers to any reactor that uses a bioprocess to produce a desired product. The term bioreactors typically refers to bio-CSTRs or chemostats, plug flow reactors, or fixed film reactors used for cell cultures or fermentation reactions. For more information on these types of reactors please see the CSTR or PFR sections of the encyclopedia.
(Pictures courtesy New Brunswick Scientific Co., Inc., Edison, NJ)
The chemical process in a bioreactor can be aerobic, anaerobic, or a hybrid of the two. Bioreactors are usually smooth and cylindrical, as shown in the examples above, and are easy to clean. This is to prevent fouling, the build-up of unwanted materials on the surface of the vessel.
Bioreactors can be used to create biodiesel from the oil of algae. In the tubular algae bioreactor shown below, algae within the tubes grow with the assistance of a light source and carbon dioxide inputs. Once enough algae has grown, it is scraped from the tube and used for its natural oils.
(Copyright W2 Energy, Inc., Carson City, NV)
The fundamental function of a fermenter is to provide a suitable environment in which microorganisms can efficiently produce target microbial products.
There are 6 types of fermenters and can be agitated either mechanically or pneumatically using injected air or gas.
TYPES OF FERMENTERS
Stirred tanks are the most commonly used fermenters due to their flexibility and they are made up of stainless steel with a polished interior to help reduce adhesion. Tower fermenters are a modified version of stirred tanks and do not require mechanical agitation but still maintain cylindrical vessels. They are normally used for fermentation of beer, yeast and Single Cell Protein (SCP). Airlift flasks are cylindrical vessels agitated by injected air from the base of the vessel. They use a gentle method of mixing and are suitable for fermentation of molds. Membrane bioreactors contain a hollow fiber system that is used extensively for cell cultivation. Bubble columns are a cylindrical vessel with a gas distributor at the bottom. More information can be found at Bubble Column . Finally, Fluidized Bed Reactor (FBR) can be used as fermenters but require a pump as their base for effective mixing.
Fermenters are composed of the following components:
Body – Higher capacities fermenters are often made of stainless steel.
Impellers – Induces uniform mixing of microorganism and nutrients.
Sparger – Introduces air below liquid level.
Jacket - Surrounds the fermenter and facilitate cooling or heating of media inside
Probes – Measures and control various process parameters.
Typical diagram of a stirred tank fermenter
(Copyright GEA Process Engineering Inc., Columbia, MD)
Fermenters are used in a variety of industries that require biological manufacturing, such as the pharmaceutical and food industries. In the pharmaceutical industry they can be used to grow cells and bacteria for drugs such as antibiotics or penicillin. They can also be used for alcoholic fermentation in breweries or even to grow yeast for bread-making.
- Simple batch design
- Process parameters can be easily varied
- Can be used for a variety of biological reactions
- Long retention times
- Constant monitoring
- Difficult sampling
GEA Process Engineering Inc. , Columbia, MD
New Brunswick Scientific Co., Inc. , Edison, NJ
W2 Energy, Inc. , Carson City, NV
Banz, Gregory. "Piloting Bioreactors for Agitation Scale-Up." Chemical Engineering Progress. 104.2 (Feb. 2008): 32-34. Print.
McNeil, B and Harvey, L. Practical Fermentation Technology. Chichester, England: Wiley, 2008.