Thermodynamics of Bioreactions

Abstract

Chapter 2 gives an overview of the many biochemical reactions occurring in a living cell, and as discussed these biochemical reactions are exploited in the biotech industry to produce many interesting compounds. The pathway activity is to a large extent determined by the kinetics of the enzymes catalyzing the individual reactions as will be discussed in Chapter 6. However, of equal importance is thermodynamic constraints, since all reactions, independent of the properties of the enzymes, have to operate according to the laws of thermodynamics. Any treatment of bioreactions is therefore not complete unless one considers the thermodynamic constraints imposed on individual bioreactions. Since usually a bioreaction is accompanied by generation of heat the thermodynamic principles are also of importance in connection with design of the heat exchangers to be installed in bioreactors. In this chapter we will take a brief look at the thermodynamics involved in bioreactions. Classical thermodynamics is a discipline, which is extensively described in many textbooks, and it is not the purpose of this chapter to give an in-depth explanation of all the fundamental thermodynamic aspects involved in cellular processes. Still, to give some understanding of the relation between growth of a microbial culture and the energy generation and consumption in the process, certain topics of thermodynamics will be briefly reviewed here. As mentioned above this will also provide a tool for an important part of bioreactor design.