Bubble Column Bioreactors

Tramper, J, Smit D, Straatman J Vlak JM (1988) Bioreactor bubble-column design for growth of fragile insect cells. Bioprocess Engineering 3 37-41. 

Bubble column bioreactors are the main competitor to airlift bioreactors, and deployment decisions are usually based on a competitive basis that excludes the stirred-tank bioreactor. Hence, studies rarely compare the stirred-tank bioreactor, bubble column, and airlift bioreactor in a more comprehensive manner. Usual comparisons are made either between the stirred-tank bioreactor and the bubble column or between the bubble column and the airlift bioreactor. The first stage in identifying a bioreactor usually involves a comparison between the stirred-tank bioreactor and bubble column bioreactor, which clarifies the bioreactor and process requirements. If the bubble column is found to be competitive, the airlift bioreactor is introduced to the discussion. 

Eig. 5. Examples of air driven bioreactors (a) bubble column, (b) draught tube, and (c) external loop. 

Eigure 6 enables a comparison to be made of kj a values in stirred bioreactors and bubble columns (51). It can be seen that bubble columns are at least as energy-efficient as stirred bioreactors in coalescing systems and considerably more so when coalescence is repressed at low specific power inputs (gas velocities). 

Fig. 6. A comparison of k a values (51). Represented are 1, stirred bioreactor using water, = 0.02 m/s, kj a (eq. 16) 2, stirred bioreactor using water, t 3 = 0.04 m/s, kj a (eq. 16) 3, bubble column using water, kj a (eq. 18) 4, stirred bioreactor using salt water, = 0.02 m/s, kj a (eq. 17) 5, stirred bioreactor using salt water, = 0.04 m/s, kj a (eq. 17) and 6, bubble column using salt water (noncoalescing).

The main part of the report describes the results of systematic investigations into the hydrodynamic stress on particles in stirred tanks, reactors with dominating boundary-layer flow, shake flasks, viscosimeters, bubble columns and gas-operated loop reactors. These results for model and biological particle systems permit fundamental conclusions on particle stress and the dimensions and selection of suitable bioreactors according to the criterion of particle stress. 

The aim of this report is to examine the principles of shear stress on particles that would allow the design of bioreactors for technical use, mainly stirred tanks, bubble columns and loop reactors. 

Special reactors are required to conduct biochemical reactions for the transformation and production of chemical and biological substances involving the use of biocatalysts (enzymes, immobilised enzymes, microorganisms, plant and animal cells). These bioreactors have to be designed so that the enzymes or living organisms can be used under defined, optimal conditions. The bioreactors which are mainly used on laboratory scale and industrially are roller bottles, shake flasks, stirred tanks and bubble columns (see Table 1). 

As is the case with pure bubble columns and gas-operated loop reactors, most bioreactors in technical use are aerated with oxygen or air. Reactors with pure surface aeration, such as roller bottles, shake flasks and small stirred reactors or special reactors with membrane aeration, are exceptions. The latter are used for the cultivation of cells and organisms which are particularly sensitive to shearing (see e. g. [28 - 29]). The influence of gas bubbles in increasing stress has been described in many publications (see e.g. [4, 27, 29, 30]). In principle it can be caused by the following processes ... 

Figure 2.27. Mixing, mass transfer and oxygen consumption in a bubble column bioreactor (Oosterhuis, 1984). Tj - reaction time constant, Xmt - ass transfer time constant, tmix -mixing time constant. ro2 - oxygen consumption rate, Vs - superficial gas velocity.

The 1980 s and the early 1990 s have seen the blossoming development of the biotechnology field. Three-phase fluidized bed bioreactors have become an essential element in the commercialization of processes to yield products and treat wastewater via biological mechanisms. Fluidized bed bioreactors have been applied in the areas of wastewater treatment, discussed previously, fermentation, and cell culture. The large scale application of three-phase fluidized bed or slurry bubble column fermen-tors are represented by ethanol production in a 10,000 liter fermentor (Samejima et al., 1984), penicillin production in a 200 liter fermentor (Endo et al., 1986), and the production of monoclonal antibodies in a 1,000 liter slurry bubble column bioreactor (Birch et al., 1985). Fan (1989) provides a complete review of biological applications of three-phase fluidized beds up to 1989. Part II of this chapter covers the recent developments in three-phase fluidized bed bioreactor technology. 

Bubble column bioreactors, 1 740-742 Bubble column reactors, static mixers in, 15 708-709... 

The dispersion of gas bubbles in a liquid is widely used in bubble column reactors and bioreactors. As shown in Figure 7.7, the gas is introduced by some kind of distributor at the bottom of the column. The liquid may be introduced at the bottom of the column and removed at the top, in which... 

Reactor in a combination of a membrane bioreactor and a bubble-column and was designed for simultaneous degradation of both hydrophilic and hydrophobic contaminants from the gas phase. 

Liibbert A, Paaschen T, Lapin A. Fluid dynamics in bubble column bioreactors experiments and numerical simulations. Bio technol Bioeng 1996 52 248-258. Johnstone RE, Thring MW. Pilot Plants, Models, and Scale-up Methods in Chemical Engineering. New York McGraw-Hill, 1957 12-26. 

Bubble columns in which gas is bubbled through suspensions of solid particles in liquids are known as slurry bubble columns . These are widely used as reactors for a variety of chemical reactions, and also as bioreactors with suspensions of microbial cells or particles of immobilized enzymes. 

K Schugerl, J. Lticke, U Oels Bubble Column Bioreactors. Tower Bioreactors without Mechanical Agitation. - R. Acton, J.D.Lynn Description and Operation of a Large-Scale, Mammalian Cell, Suspensio Culture Facility. -S. Aiba, M. Okabe A Complementary Approach to Scale-Up Simulation and Optimization of Microbial Processes. - LKjaer-gaard The Redox Potential ItUseandControl in Biotechnology. 

Fig. 1. Different types of bioreactors for plant cell, tissue and organs. (A) mechanically-agitated bioreactors, a aeration-agitation, b rotating drum, c spin filter. (B) air-driven bioreactors, a bubble column, b draft tube, c external loop, (C) non-agitated bioreactors, a gaseous phase (mist), b oxygen permeable membrane aerator, c surface aeration, (D) light emitting draft tube...

Flower [25], Panda et al. [26], Doran [27]. and Payne et al. [28]. Several kinds of bioreactors, such as the stirred tank bioreactor with hollow paddle and flat blade impellers, the bubble column, the airlift bioreactor with internal and external loops, the rotating drum bioreactor, the stirred-tank with a draft tube, and the mist bioreactor have been attempted for plant cell, tissue and organ cultures (Fig. 1). 

Monitoring of large-scale fed-batch manufacture of baker s yeast was also possible with the electronic nose [33]. The cultivation took place in a 200-m3 bubble-column reactor. The monitoring procedure is complicated by the large phase variation and circulation times in the bioreactor. On the 200-m3 scale, ethanol and biomass were predicted but with lower accuracy than in the laboratory (10%). The data was compensated for increasing reactor liquid volume and aeration rate during the fed-batch cycle, simply by including these variables in the inputs to the ANN. 

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