Industrial Microbiology

Parameters Controlled in a Fermenter

Written by MicroDok

The success of a particular fermentation process depends on the existence of defined environmental parameters for biomass buildup and product formation. It is in view of this that the physical and chemical parameters of the fermentation process including temperature, pH, oxygen, gases and pressure in the fermentation medium have to be kept constant during the process. In order to optimize the productivity and product yield of a fermentation process, and thus ensure the reproducibility of the entire process, it is critical to effectively monitor and control the parameters that affect the optimal growth of the organisms and the entire fermentation process. Several parameters including foam formation, temperature, pressure, oxygen and carbondioxide as aforementioned affect the optimal functioning of a fermentation process. And it is critical to control these factors so that the metabolic process of the organism and product yield can be optimized. Most modern fermentation vessels are fitted with sensors and computer systems that help in the effective monitoring and control of the physical and chemical parameters that affect fermentation processes.

FOAM FORMATION

Foam or bubbles are dispersions of gases in liquid. Fermentation medium are usually composed of liquid medium or broth, and this allows foam to form during the fermentation process. The formation of foam in a fermentation vessel is usually as a result of the agitation and aeration that are paramount in the optimal growth of the organisms. The presence of surface-active agents such as proteins in the fermentation medium can also contribute to foam formation. Despite the significance of foam formation in some industrial fermentation processes such as in beer fermentation (where foam head retention is a desirable quality in beers), foam formation still presents some undesirable microbiological, economical and chemical engineering consequences in some fermentation processes. Thus foam formation must be controlled in fermentation processes in order to ensure optimal growth of the organism and product yield. Foam reduces the total fermentation, and it reduces the transfer rate of oxygen in the fermentation vessel. Rapid foam formation affects the rate of aeration and agitation in the fermentation vessel. Foam formation is a source of contamination, and it could reduce the yield of the desired product. Foam formation in industrial fermentations is controlled using chemical and mechanical means. Anti-foaming agents or defoamers are chemical agents used to breakdown foam in a fermentation vessel once they are formed.

TEMPERATURE

The control of temperature in a fermentation vessel is important because many fermentation processes release heat; and if not controlled, it could affect the entire process and move the temperature to levels that may affect the optimal growth of the fermentation organism. Industrial fermenters are usually fitted with thermometers that are linked to the cooling and heating systems of the fermentation vessel; and these thermometers help the personnel to monitor changes in temperature levels of the fermenter. Heat is generated in a fermentation vessel via microbial activity and mechanical agitations. If the heat generated does not support the optimal growth of the organism, it is of the best interest of the fermentation process to remove the generated heat from the fermentation vessel. Most industrial fermenters are fitted with internal heating coils or external heating jackets through which cold water can easily be introduced to the vessel to control the temperature and bring it to an optimum temperature level that will support the growth of the organism. Normally, refrigerated water is circulated in cooling pipes within the fermenter. When the temperature of the fermenter is low, the temperature of the fermentation vessel could be raised through the heating coils of the vessel.

pH

Many fermentation processes yield or produce products that alter the optimal pH of the fermentation medium and other reactants in the vessel. Thus, it is critical to control the pH of the system via the addition of acid or base in the form of buffering agents or buffers. Most fermentation media contain buffering agents such as phosphates and salts like calcium carbonates that help to control the pH of the system or process. Industrial fermenters are usually fitted with pH meters or electrodes – which gives a measurement of the pH level of the fermenter. Changes recorded on the pH meter will either cause the addition of an acid or base in order to bring the fermentation process to an optimum level required for optimal microbial growth and product yield.

 GASES (CO2)

Gases such as carbondioxide (CO2) can affect the rate of fermentation if not controlled when produced. Once the carbondioxide level of the fermentation process is known, it will help to give an estimate of the carbon balance of the fermentation medium or mixture. This will help to determine the course of the fermentation process.

 PRESSURE

Pressure is vital to every fermentation process. Once a positive pressure is maintained in a given fermentation process, possible contamination of the process will be eliminated. A positive pressure also helps to ensure stable aeration of the fermentation medium for the optimal growth of the organism. Pressure levels of the fermentation vessel are determined with the aid of specialized instruments such as manometers fitted in the fermenter.

 OXYGEN

Oxygen is critical to the optimal growth of aerobic organisms; and optimal oxygen fermentation is therefore an important factor to be considered in aerobic fermentation processes. This is because most fermentation processes are operated aerobically; and for optimization of microbial growth and product yield, it is important to ensure proper supply of oxygen to the system.

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