Fermentation is the process of breaking down a substance to its simpler components in order to produce specific chemical and/or physical changes in the media. Fermentation occurs in vessels called bioreactors (or fermenters) that are designed to maintain an optimal environment for the organic material to be cultivated.
Requirements for an optimal fermentation environment
As mentioned previously, a bioreactor is the core of biological processes since this is the place where all microbiological and biochemical reactions take place. More specifically, this is a vessel that is designed to provide an effective environment for enzymes or whole cells to transform biochemical matter into products.
What does an effective environment mean exactly?
In terms of bioreactors, this means ensuring a sufficient gas supply, maintaining the right pH-levels and temperature, and providing nutrients, acids, bases, anti-foam or oxygen to successfully maintain growth. To perform all these functions, an appropriate pump technology must be implemented.
Bioprocess engineers need to consider the following factors while choosing the right pump:
As higher viscosities of fluids create higher forces on a pump, the pump needs to be robust enough, and additionally, equipped with a motor that provides the right level of drag torque.
Sensitivity of the fluid to shear-forces
Some fluids are very sensitive to shear-forces placed upon them, hence, the right pump should ensure a gentle pumping motion that does not lead to altering the fluid components (i.e. destroying cells in the fluid due to high shear-forces).
Accuracy and Precision
Accurate and precise delivery of the organic fluid to the bioreactor is an important aspect of the fermentation process. The achievable accuracy and precision depend largely on the pump technology. In order to achieve as good accuracy and precision as possible, calibration and usage of sensors can help to overcome limitations inherent to certain pump technologies.
The most important role that pumps play in fermentation is to regulate the many critical ingredients that go into a bioreactor. This includes measuring and controlling the pH-levels, feeding nutrients, measuring the pressure, and preventing foam formation.
Nutrient Feed Pump (1)
During a bioprocess, microorganisms normally consume a wide range of nutrients, including water or highly viscous glucose solutions, which are delivered through the pump. In addition, it is necessary to provide various feed profiles so that pumps are able to ramp up fluid supply exponentially, which can be desired in a bioreactor.
Acid and Base Pumps (2,3)
Adding acid or base is sometimes necessary to maintain the desired environment within the bioreactor. This is usually indicated by detecting the pH level inside the device. The substances are added to the culture vessel through tubes and pumps, but their concentration needs to be skilfully attained.
Anti-foam Pump (4)
Foam is usually an undesired side effect of the fermentation process in bioreactors as it can block the flow of gas. In this case, pumps are used to control the formation of foam, and if necessary, pump in the anti-foam fluid to control foam.
Considering the requirements in bioreactors, the ideal pump technology is peristaltic pumps. They stand out due to their ability to accurately and gently feed liquids, even with high viscosities, and to maintain the integrity of each fluid. Moreover, the fact that in peristaltic pumps tubes are the only components, that come in contact with the medium makes it easier to follow a high sanitary standard by using high quality tubing.