A theoretical model for catalyst‐fluid flow reactors with immobilised cells

Abstract

A theoretical model of the behaviour of immobilised cells in porous pellets is developed. Particular attention is given to ethanol production with immobilised yeast cells, the deactivating effect of the alcohol upon the cells and the performance of the reactor. It is demonstrated that by introducing an activity parameter, which is a measurable quantity, all of the effects of immobilisation, decreased activity, increased operational stability and increased thermal resistance, yield to a quantitative description. This description is given in terms of parameters that govern the diffusion and reaction phenomena in the pellet and the dynamics of the cell population in free form. The effects of ethanol are accounted for by treating it as a deactivator acting in series with the main reaction. In this way it can be shown that its action manifests itself by increasing a natural decay constant of the cell system. The growth of the cell population inside the pellet is taken into account. Immobilised enzyme reactors may be considered a special case of heterogeneous biocatalytic reactors in which no growth takes place. The model is able, therefore, to describe enzyme systems under analogous conditions of deactivation‐reaction or under natural irreversible decay.