Fundamental Bioengineering

7Kinetics of Bio-Reactions

John Villadsen

Summary

Mechanistically founded rate expressions are derived for enzyme reactions, and in Linewaever–Burk plots of 1/r versus. 1/s, it is shown how the kinetic and thermodynamic parameters are calculated from experiments. Kinetic expressions for cell reactions are set up by analogy with the enzyme kinetic expressions. Conditions for which the cell kinetic models are valid are stated. In an industrially relevant example, the kinetics for succinic acid production is derived from experiments. Examples show that simple rate expressions for cell reactions are invalid. Kinetic models and models for transport of substrate into pellets are combined. Finally, an introduction is given to metabolic control analysis.

In Chapter 2, the rates of bioreactions were defined both for enzymatically catalyzed reactions and for reactions with living cells. The rates of the reactions were measured in a steady-state CSTR through measurement of the outlet concentrations of reactants. These rates were empirical quantities, valid only for the environmental conditions of the experiment, for example, the dilution rate D.

In this chapter, the specific rates of reaction will be predicted by means of a mathematical expression, the kinetics of the reaction. This expression can be derived through a mechanistic interpretation of an enzymatically catalyzed reaction, but it is essentially of empirical nature for cell reactions. The models can be used in mass balances ...