ABSTRACT
In Chapter 1 it was stated that stability of the biocatalyst is one of the crucial parameters for the overall volumetric productivity of the bioreactor. In this chapter some aspects of enzyme stability are discussed in more detail. As result of their macromolecular structure all enzymes are liable to inactivation at slower or faster rates, depending on the enzyme and the conditions. In principle, the material discussed applies to biocatalysts in general (enzymes, cell organelles and whole cells), provided that the biocatalyst is used for a bioconversion and one enzyme is rate and stability limiting. In biomass production or production of metabolites by growing or at least viable cells, viable-cell stability is crucial. This can be discussed on the basis of the "death" rate of cells, to be added to the specific growth rate. It will not be discussed in this chapter. Mechanical stability or sensitivity to shear and other hydrodynamic forces of fragile cells will be treated separately in Chapter 8.
