Mathematical models for the product accumulation in microbiolgical processes

A production model consisting of one or more exponential decay functions is proposed to represent the rate of accumulation of a product per unit weight of cell. This, together with a cell age distribution function, is used to describe the product accumulation in a fermentation process. This postulate offers a unified concept applicable to both batch and continuous processes as well as problems arising from environmental changes. The idea is compatible with the current understanding of microbial physiology. It offers an interpretation for the controversy over cell‐product ratios observed in some batch and continuous fermentations when treated as conventional chemical reaction. The proposed postulate fits reasonably well with the lysine and lactic acid processes.