Perfect bioreactor

The characterization of bioreactors is not limited to the standardization of stirred tank type reactors (Dechema, 1982) It also includes ideal reactors as model types in a wider framework. The problem of defining a perfect bioreactor, including tests of pseudohomogeneity (Moser, 1983a) will be discussed later. 

The process kinetic analysis is carried out in two different types of reactors. The so-called perfect bioreactor is used for obtaining true kinetic data. This laboratory reactor must therefore meet certain requirements with regard to all possible transport phenomena (see Sect. 4.2). A so-called bioreactor model is a scaled-down bioreactor with some geometrical similarity to the production unit. Here, significant transport phenomena (cf. Chap. 3) can be studied and quantified with a physical system in a first step. 

Finally, there is a precautionary rule Kinetics should always be measured in two different reactors to identify any hidden variables or parameters. In addition to experimenting in a perfect bioreactor, one should also evaluate a trial in the pilot plant. This testing has another purpose as well, which might be called kinetic similarity (Moser, 1978b) (as exists, e.g., between DCSTRs and CPFRs). Real biological processes are so complex that altered flow... 

Perfect Bioreactors in Bench and Pilot Scale for Process Kinetic Analyses... 

In a bioreactor, one is interested in the transfer per unit of volume of reactor, called Kia or the volumetric mass-transfer coefficient, a is the interfacial surface area per unit of volume of liquid. In a perfectly mixed tank, C has identical values at any point and C depends on the conditions in the gas phase at the outlet of the reactor. Several authors [60] consider that a better estimate of the driving force is given by the logarithmic mean concentration difference between the entry and the exit of gas. 

The aerobic bioreactor is a tank measuring 32 m in diameter by 6 m in height, which gives a useful volume of about 5000 m. It has four ABS pumps, each with a power of 45 kW, by means of which the content of the reactor is constantly recirculated at a rate of 1400 m /h per pump, with the objective, obtaming perfect homogenization inside the reactor. 

The application of interpretative models has been hampered by the technical challenges in collecting adequate data on-line, and as a result, to date bioreactor models have been of the predictive type. Some general conunents can be made about such models First, due to the heterogeneity of SSF systems, a spatial variable is often involved, which leads to partial differential equations and therefore makes solution of the equations more difficult than would occur in perfectly mixed systems. Second, the sophistication of the model and the detail with which it describes the system depend on the complexity of the system and the motivation behind the modeling work. 

Here we have also recognized that if the contents of the bioreactor are perfectly mixed, JCj = j cstbr- Algebraic manipulation of equation (13.2.58) combined with use of the definition of the dilution rate yields... 

The CSMB is a configuration where the bioreactor contents are perfectly mixed and uniform throughout. In this instance, a lumped parameters model could be applied. The composition of the outlet flow is constant, and is the same as the flow in the reactor. 

Mechanically stirred vessels Mixing is promoted by mechanical stirring (occasionally magnetic in bench-scale vessels) using different impeller types. In addition, aeration is also employed to augment mixing. In this most commonly used type of bioreactor, the tank content is perfectly mixed and hence uniform in composition. 

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 ... 

Figure 1.11 (a) The top floor of an installation of 10 bioreactors (55 m ) for microbial production of secondary metabolites. Such installations, if well maintained, can remain in perfect operating condition for several decades while being entirely depreciated. The control room is at the end of the hall (not visible). 

First, the advances in molecular biology will enable a much broader range of bioproducts, produced via fermentation by computer-designed cells and microorganisms, perfectly tuned to the continuously changing environment in large-scale bioreactors, with maximum carbon and energy conversion efficiencies. 

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