Continuous stirred-tank bioreactor

The mass transfer, KL-a for a continuous stirred tank bioreactor can be correlated by power input per unit volume, bubble size, which reflects the interfacial area and superficial gas velocity.3 6 The general form of the correlations for evaluating KL-a is defined as a polynomial equation given by (3.6.1). 

Breese, T.W. and Admassu, W. (1999) Feasibility of culturing c2cl2 mouse myoblasts on glass microcarriers in a continuous stirred tank bioreactor. Bioprocess Eng. 20, 463-468... 

While the Monod equation is an oversimplification of the complicated mechanism of cell growth, it often adequately describes fermentation kinetics. The Monod kinetic parameters can be determined by making a series of ideal continuous stirred-tank bioreactors, which will be discussed later. Table 19.6 shows the typical values of the Monod s kinetic parameters when glucose is a limiting substrate. 

Eor an ideal continuous stirred-tank bioreactor (CSTB), the concentrations of the various components of the outlet stream are assumed to be the same as the concentrations in the bioreactor. Continuous operation of a bioreactor can increase the productivity of the reactor significantly by eliminating the downtime and the ease of automation. 

Sokol, W, and Migiro, C.L.C. (1996), Controlling a continuous stirred-tank bioreactor degrading phenol in the stability range, The Chemical Engineering Journal and The Biochemical Engineering Journal, 62(1) Cl-12. 

Steady-state flow reactors, with a constant supply of reactants and continuous removal of products, can be operated as both a continuous stirred-tank bioreactor (CSTB) and as a plug flow bioreactor (PFB). It is possible to have different configurations of the membrane bioreactor where the biocatalyst is immobilized in the fractionated membrane support (Katoh and Yoshida, 2010). In Fig. 1.6 the scheme of a CSMB in which the biocatalyst is immobilized on the surface of the membrane beads is presented. The biocatalyst immobilized in the porous structure of a fractioned membrane can also be operated in CSMB. For example, two configurations are shown in Fig. 1.7 (a) for flat-sheet and (b) for spherical porous structures, respectively. Such structures could also be adopted for PFB, where a bed of membrane support with the immobilized biocatalyst could be utilized, in either a fixed or fluid configuration. 

Krebser, U., H. P. Meyer, and A. Fiechter, A Comparison between the Performance of Continuously Stirred-Tank Bioreactors and a TORUS Bioreactor with Respect to Highly Viscous Culture Broths, J. Chem. Tech. Biotechnol., 43, 107, (1988). 

Suppose that the fed-batch bioreactor in Fig. 2.11 is converted to a continuous, stirred-tank bioreactor (also called a chemostat) by adding an exit stream. Assume that the inlet and exit streams have the same mass flow rate F and thus the volume of liquid V in the chemostat is constant. 

A chemostat is a continuous stirred tank bioreactor that can carry out fermentation of a plant cell culture. Its dynamic behavior can be described by the following equations ... 

Younesi, H., et al., 2008. Biohydrogen production in a continuous stirred tank bioreactor from synthesis gas by anaerobic photosynthetic bacterium Rhodopirillum rubrum. Bioresource Technology 99 (7), 2612—2619. 

Bioreactors a) batch stirred tank b) continuous stirred tank c) continuous packed-bed i) downward flow, ii) upward flow and iii) recycle d) continuous fluidised-bed e) continuous ultrafiltration. Redrawn from Katchalski - Katzir E. (1993) Trends in Biotechnology II, 471-477. 

Fig. 4.1. Instrumentation control for continuous stirred tank (CSTR) bioreactor.

Figure 11.9 Different arrangements and modes of operation for membrane bioreactors Continuous Stirred Tank Reactor (CSTR) with recirculation arrangement (a), dead-end cell (b), tubular with entrapped enzyme (c).

Similar behavior to that of the nonisothermal CSTR system will be observed in an isothermal bioreactor with nonmonotonic enzyme reaction, called a continuous stirred tank enzyme reactor (Enzyme CSTR). Figure 3.27 gives a diagram. 

The production of substances that preserve the food from contamination or from oxidation is another important field of membrane bioreactor. For example, the production of high amounts of propionic acid, commonly used as antifungal substance, was carried out by a continuous stirred-tank reactor associated with ultrafiltration cell recycle and a nanofiltration membrane [51] or the production of gluconic acid by the use of glucose oxidase in a bioreactor using P E S membranes [52]. Lactic acid is widely used as an acidulant, flavor additive, and preservative in the food, pharmaceutical, leather, and textile industries. As an intermediate product in mammalian metabolism, L( +) lactic acid is more important in the food industry than the D(—) isomer. The performance of an improved fermentation system, that is, a membrane cell-recycle bioreactors MCRB was studied [53, 54], the maximum productivity of 31.5 g/Lh was recorded, 10 times greater than the counterpart of the batch-fed fermentation [54]. 

In this operation mode, it is possible to mitigate the major limitation of continuous cultures, that is, the low productivity due to the loss of cells in the bioreactor outlet. In perfusion, this issue is overcome by using a cell retention device to maintain cells inside the bioreactor. Figure 9.17 shows a scheme of a stirred-tank bioreactor operating in perfusion mode, as well as the kinetic behavior of a perfusion run. 

A third type of bioremediation involves the use of a bioreactor in a dedicated treatment area. The contaminated soil is excavated, slurried with water, and treated in the reactor. The horizontal drum and airlift-type reactors are usually operated in the batch mode but may also be operated in a continuous mode. Because there is considerable control over the operating conditions, treatment often is quick and effective. Contaminated groundwater and effluent also may be treated in either fixed-film or stirred-tank bioreactors. However, bioreactors are still in the developmental stages and further research is required to optimize their efficiency and cost effectiveness (Wilson and Jones 1993). 

Two fundamentally different types of bioreactor setups can be distinguished. In the first type of reactors, MTBE-degradation occurs by bacteria in suspension in continuously stirred tank reactors (CSTR) (Table 6). An obvious advantage of this setup is the optimal mixing of MTBE-degrading biomass, contaminants and oxygen, reducing transport Hmitations to a minimum. However, specialized adaptations are required to prevent washout of biomass from the reactor. Three different methods exist. 

Continuous Flow Stirred Tank Bioreactors and Chemostats... 

To choose the adequate bioreactor design for continuous PHA production, kinetics for both biomass and PHA production by the microbial strain should be considered. In the case of PHA production directly associated with microbial growth as it is found in Alcaligenes latus DSM 1122 on sucrose [128], or for Pseudomonasputida ATCC 29147 on fatty acids [97,98], a one-step continuous process using a continuous stirred tank reactor (CSTR) is a viable solution. 

Laska ME, Cooney CL. (2002) Bioreactors, continuous stirred-tank reactors. In FUckinger MC, Drew SW, editors. Encyclopedia of Bioprocess Technology, John Wiley Sons, Inc., New York, USA. p 353-371. 

A similar approach, starting with a material balance, can be used for the characterization of bioreactors operating in the continuous mode. Thus, for a perfectly mixed reactor, or continuous stirred tank reactor (CSTR), where the term of accumulation is zero at steady state and the liquid composition is uniform, the material balance for substrate A is given by Equation 7.7 ... 

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