Bioprocess kinetics

Model building is considered here as an adaptive process (cf. Fig. 2.18) It involves stepwise fitting of the parameters, fe, and discrimination of the function, /, itself. All of the models in this chapter should be considered as working hypotheses. The nature of formal kinetic descriptions means that other mathematical functions can always be found that serve the same descriptive function to within the precision of the measurements (see Esener et al, 1983). The lack of basic content in formal kinetic models in comparison with structured models (Harder and Roels, 1981 Roels and Kossen, 1978) can to some extent be compensated for by subsequent analysis (Esener et al., 1983 A. Moser, 1978b, 1984a). 

To a large extent, the formal kinetic analysis techniques presented in this chapter relate to discontinuous batch operations. Even if the goal is a continuous operation, the batch process kinetic model serves as a start-up. The most significant element of a kinetic analysis is the time dependence of the macroscopic process variables mentioned in Chap. 2. Bacteria, molds, viruses, and yeasts all have different reproduction mechanisms, and formulating a structured kinetic model more closely related to the actual mechanism is a desirable goal. More structured models are desirable not only to deal with active cells but also to extend kinetic analysis to more complex situations involving inactive cells, mixed populations of cells, multiple substrates, and 

1 Temperature Dependence, k(T), Water Activity, a v, and Enthalpy/Entropy Compensation 

In Equ. 2.53, the very general model equation r = /(x, fc) is shown separated into concentration- and temperature-dependent parts. The reaction rate constants are therefore regarded as temperature dependent, as illustrated with type 3 in Fig. 4.12. 

For a general equation, especially one for use in food technology (e.g., drying processes), the water concentration or water activity, should be incorporated. The water activity is defined as 

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Conversion rate data obtained under a wide range of operating conditions may be worked out to provide a kinetic expression, most typically expressed according to well established models for bioprocess kinetics first and second order, Monod, Haldane, product-inhibited, etc. 

Jemec, K. R, Raspor, P. (2005) Initial Saccharomyces cerevisiae concentration in single or composite cultures dictates bioprocess kinetics. Pood Microbiology, 22, 293-300. 

Most commercial bioreactions are carried out in batch reactors. The design of a continuous bioreactor is desired since it may prove to be more economically rewarding than batch processes. Most desirable is a reactor that can sustain cells that are suspended in the reactor while growth medium is fed in, without allowing the cells to exit the reactor. Focus mixing modeling, separations, bioprocess kinetics, reactor design. 

Bioprocess technology and its working principles used for planning, evaluating, and calculating (modeling) bioprocesses (kinetics and reactors). 

Figure 1.4. Flow chart sheet of the strategy of bioprocess kinetic analysis for different process situations stationary/instationary, homogeneous/heterogeneous, differential/ integral, and true dynamic/balanced (frozen) reactor operation, rds, rate-determining step qss, quasi-steady-state, (From Moser, A. 1983.)...

Contribution of Enzyme Mechanism to Bioprocess Kinetic Models... 

Contribution of Chemical Kinetic Laws to Bioprocess Kinetic Modeling... 

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