INFLUENCE OF AGE AND STRUCTURE OF PENICILLIUM-CHRYSOGENUM PELLETS ON THE INTERNAL CONCENTRATION PROFILES

Pellets of Penicillium chrysogenum which were spontaneously formed aft er a certain stage of a batch fermentation, displayed a considerable s tructural change in course of their lifetime. Microelectrode studies s howed the internal mass transport properties of these pellets (diamete r 1-3 mm) to be highly effected by their morphological structure. Rela tively young pellets, in an early stage of the batch fermentation, pos sessed a homogeneous and dense structure. These pellets were only part ly penetrated by oxygen (ca. 70 mum) at air saturated bulk conditions. Older pellets, in a final stage of the batch fermentation, were strat ified and fluffy. They were completely penetrated by oxygen due to a d ecreased activity and a higher diffusivity. Investigations with glucos e microelectrodes revealed that glucose consumption inside pellets of all lifetimes exclusively occurred in the periphery, indicating that g rowth was restricted to these regions only.