Column Fermenter

Fermenters are usually classified based on their vessel type such as tank, column, or loop fermenters. The tank and column fermenters are both constructed as cylindrical vessels. They can be distinguished based on their height-to-diameter ratio (H/D) as (Schiigerl, 1982)  

A loop fermenter is a tank or column fermenter with a liquid circulation loop, which can be a central draft tube or an external loop. 

Vessel Type Compressed Air Internal Moving Parts External Pumping  

Column bubble column multistage sieve tray 

Loop air-lift pressure cycle propeller loop jet loop 

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The most simple fermenter is the bubble column fermenter (or tower fermenter), which is usually composed of a long cylindrical vessel... 

To overcome the weaknesses of the column fermenter, several alternative designs have been proposed. A tapered column fermenter [Figure 6.21 (b)] can maintain a high air-flow rate per unit area at the lower section of the fermenter where the cell concentration is high. 

Fig. 6.21 Column fermenters (a) bubble column, (b) tapered bubble column, (c) sieve-tray bubble column, (d) sieve-tray column with external pumping, and (e) packed-bed column with external pumping.

A loop fermenter is a tank or column fermenter with a liquid circulation loop, which can be a central draft tube or external loop. Depending on how the liquid circulation is induced, it can be classified into three different types air-lift, stirred loop, and jet loop (Figure 6.22). 

Slurry Bubble Column Reactors As in the case of gas-liquid slurry agitated reactors, bubble column reactors may also be used when solids are present. Most issues associated with multiphase bubble columns are analogous to the gas-liquid bubble columns. In addition, the gas flow and/or the liquid flow have to be sufficient to maintain the solid phase suspended. In the case of a bubble column fermenter, the sparged oxygen is partly used to grow biomass that serves as the catalyst in the system. Many bubble columns operate in semibatch mode with gas sparged continuously and liquid and catalyst in batch mode. 

Fig. 1 Bubble column fermenter. (View this art in color at WWW. dekker. com.)...

Tubular fluidized and fixed bed fermenters are deviations from the simple bubble column fermenter. Often utilized in producing beer and ciders, these fermenters contain immobilized microorganisms or microbial films on support surfaces. Microbes lost with the product are continuously replenished by adding fresh microorganisms into the packed bed fermenters. In the fixed bed case, slow downward flow of the medium significantly reduces the shear removal (mobilization) of the microbes from the support materials and increases the residence time in the packed column. This is a typical characteristic of the trickle bed fermenter for continuous operation. Readers are referred to the packed bed reactor entry in this volume for a more... 

The submerged process takes 3 to 10 d to complete, depending on the method used. Although very high yields are possible, the productivity is a more important consideration on an industrial basis. It is rare that the process is allowed to continue to the maximum yield. The typical kinetics of citric fermentation in a bubble column is shown in Fig. 7 and the kinetics of high yield (up to 360 g/1) in a fed-batch bubble column fermentation is shown in Fig. 8. 

The most simple fermenter is the bubble column fermenter (or tower fermenter), which is usually a long cylindrical vessel with a sparging device at the bottom as shown in Figures 19.5a and b. The fermenter contents are mixed by rising air bubbles that also provide the oxygen needs... 

To overcome the weaknesses of the column fermenter, alternatives have been proposed. A tapered column fermenter can maintain a high airflow rate at the lower section of the fermenter where the cell concentration is high. Several sieve plates can be installed in the column for the effective gas-liquid contact and the breakup of the coalesced bubbles. The cylindrical column can be divided into multiple stages with stirrers. This configuration is analogous to stirred-tank fermenters connected in series. To enhance the mixing, the fermentation broth can be recirculated by using a pump. 

A column fermenter is a fixed-bed reactor. The solid medium is put into the column with provision at both ends for aeration. Sterile air can be supplied either by a radial or axial gradient method. The water activity is maintained by humidified air. The temperature for the solid fermentation is monitored and controlled by recycling water in the jacket from an isothermal bath. In a fixed-bed... 

A column fermenter developed by Saucedo-Castaneda et al. [29] is a typical example. 

Kawagoe, M., Hyakumura, K., Suye, S., Miki, K., Naoe, K., 1997. Application of bubble-column fermenters to submerged culture of schizophyllum-commune for production of L-malic acid. Journal of Fermentation and Bioengineering 84 (4), 333-336. 

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