Dynamics of Microbial Propagation : Models Con - sidering Inhibitors and Variable Cell Composition

Mathematical models for microbial growth in batch and continuous cultures are formulated. The models have been referred to as distributed models since the microbial population in a culture is looked upon as protoplasmic mass distributed nniformly throughout the culture. Growth is regarded as the increase in this mass by conversion of medium components into biological mass and metabolic products. Two sets of models have been presented. The first arise from inkoducing additional considerations into the model proposed by Nonod to account for ihe stationary phase and the phase of decline in a batch culture. These have been referred to as unstructured, distributed models since t,hey do not recognize any form of structure in the protoplasmic mass. The models in the second set are referred to as structured, distributed models. Structure is introduced by considering the protoplasmic mass to be composed of two groups of substances which interact wit.h each other and with substances in the environment to produce growth. The structured models account for the dependence of growth on the past history of t,he cells; thus they predict all growth phases observed in batch cultures, whereas the unstructured models do mot predict a lag phase. The full implications of the models for continuous propagation, as determined by the method of stability analysis and transient calculations, arc discussed. The models predict a number of new results and should be confronted with experiments.