Industrial fermenter are either of anaerobic or aerobic classes. Anaerobic fermenters do not require much special equipment, except for the removal of heat generated during the fermentation process; on the contrary, aerobic fermenters require much elaborate equipment for adequate mixing and aeration.

The industrial fermentation processes are mostly aerobic, thus a typical aerobic fermenter is shown in figure and its parts have been discussed below.

Cooling Jacket

Large-scale industrial fermenters are made up of stainless steel. A fermenter is a large cylinder closed at the top and fitted with various pipes and valves at the bottom. The fermenter is fitted with a cooling jacket on the external surface, and through this jacket steam (for sterilisation) or cooling water (for cooling) is passed.

Cooling jacket is an essential part because sterilisation of the nutrient medium and removal of the heat generated are mandatory for completing the fermentation process successfully. In large fermenters, heat transfer occurs insufficiently through the jacket, and thus, internal coils are provided to pass through either steam or cooling water.

Aeration System and Stirring

Aeration system forms an essential part of a fermenter. The oxygen demand by the culture, in a fermenter with a high microbial population density, is tremendous; but since oxygen is poorly water-soluble, it barely transfers rapidly through the growth medium. Therefore, precautions should be taken and two separate aeration devices (sparger and impeller) should be used to ensure proper aeration and oxygen availability in the fermenter throughout the culture.

Sparger is a series of holes in a metal ring or a nozzle through which filtersterilised or oxygen-enriched air enters the fermenter under high pressure as a series of tiny bubbles from which the oxygen passes by diffusion into the liquid culture medium.

Impeller (or agitator) is an agitating device required for stirring of the fermenter. Stirring achieves mixing of the gas bubbles and of the microbial cells through the liquid culture medium. Thus, stirring ensures uniform access of microbial cells to the nutrients.

The impeller’s size and position in the fermenter depends on the fermenter’s size. Idyllically, the impeller should be 1/3^th of the fermenter’s diameter and should be positioned above the fermenter’s base. The number of impeller to be fitted also depends on the size of fermenter. More than one impeller is equipped in tall fermenters in order to obtain satisfactory aeration and agitation.

Baffles

Baffles are equipped in the fermenters of all sizes. They prevent vortex and improve the efficiency of aeration. They are metal strips of 1/10^th of fermenter’s diameter and are attached radially to the walls.

Controlling Devices for Environmental Factors

In microbial fermentation, growth and product formation should be measured and also the environmental parameters (such as temperature, oxygen concentration, pH, cells mass, levels of key nutrients, and product concentration) should be controlled throughout the process using various devices in a fermenter.

Use of Computer in Fermenter

Computer technology has put a remarkable influence in fermentation process and computers are used to model fermentation processes in industrial fermenters. Integration of computers into fermentation systems is based on their capacity for process monitoring, data acquisition, data storage, and error-detection.

Some online data analysis functions include the acquisition measurements, data verification, filtering, unit conversions, calculation of indirect measurements, differential integration calculations of estimated variables, data reduction, tabulation of results, graphical presentation of results, process stimulation, and data storage.