Influence of substrate transport on the activity of immobilized Papaver somniferum cells

Abstract

Intraparticle diffusion resistance was studied for Papaver somniferum cells immobilized by Ca alginate gel. In callus tissue, these plant cells convert codeinone to codeine. First, the diffusion rates of substrates in the gel were measured, followed by investigation of the consumption rates of the substrates by free cells. The consumption rate of sucrose was zero order in relation to sucrose concentration, whereas that of codeinone was first order in relation to its concentration. The oxygen consumption rate obeyed Michaelis-Menten type kinetics with respect to dissolved oxygen concentration. Combining the reaction rates and diffusion rates allows calculation of the extent of the effect of diffusion limitation on the overall reaction rates. The analysis showed that the effectiveness factor for each substrate was about unity and that the influence of diffusion resistance was negligible. However, the oxygen concentration decreased considerably inside the particle, and this may affect the activity of the plant cell for repeated use over a long time period. Thus, deactivation proceeds due to the oxygen deficit although the temporal reaction rate is not affected.