MODELING AND MEASUREMENTS OF FUNGAL GROWTH AND MORPHOLOGY IN SUBMERGED FERMENTATIONS

Generalizing results from fungal fermentations is difficult due to the ir high sensitivity toward slight variation in starting conditions, po or reproducibility, and difference in strains. In this study a mathema tical model is presented in which oxygen transfer, agitation intensity , dissolved oxygen tension, pellet size, formation of mycelia, the fra ction of mycelia in the total biomass, carbohydrate source consumption , and biomass growth are taken into account. Two parameters were estim ated from simulation, whereas all others are based on measurements or were taken from literature. Experimental data are obtained from the fe rmentations in both 2 L and 100 L fermenters at various conditions. Co mparison of the simulation with experiments shows that the model can f airly well describe the time course of fungal growth (such as biomass and carbohydrate source concentrations) and fungal morphology (such as pellet size and the fraction of pellets in the total biomass). The mo del predicts that a stronger agitation intensity leads to a smaller pe llet size and a lower fraction of pellets in the total biomass. At the same agitation intensity, pellet size is hardly affected by the disso lved oxygen tension, whereas the fraction of mycelia decreases slightl y with an increase of the dissolved oxygen tension in the bulk. All of these are in line with observations at the corresponding conditions. (C) 1998 John Wiley & Sons, Inc.