A SIMPLE STRUCTURED MODEL DESCRIBING THE GROWTH OF STREPTOMYCES-LIVIDANS

The growth of Streptomyces lividans in defined media was modeled using a simple structured growth model. Conventional unstructured models li ke Monod kinetics, substrate inhibition kinetics, and the logistic equ ation were also used in an attempt to fit the data, but the results we re all unsatisfactory. The main reason for failure in applying simple unstructured models is that they cannot describe the long lag phases s ometimes observed during growth of S. lividans. The simple structured growth model was derived along similar principles to cybernetic growth models. This model quite accurately describes the growth of S. livida ns. It assumes that the rate of assimilation of a substrate depends on the concentration of a specific key enzyme. This key enzyme is only p roduced in the presence of the substrate, and it is broken down at a s teady rate. An enzyme synthesis allocation variable, w, similar to the cybernetic variable, u, described in cybernetic growth models, is pro posed to control enzyme synthesis. Until the key enzyme concentration approaches its maximum level, very little substrate is consumed. And c onsequently, the lag phase is sustained. (C) 1998 John Wiley & Sons, I nc.