KINETIC MODELING OF POLY(BETA-HYDROXYBUTYRATE) PRODUCTION AND CONSUMPTION BY PARACOCCUS-PANTOTROPHUS UNDER DYNAMIC SUBSTRATE SUPPLY

The objective of the research was to obtain insights into the behavior of microorganisms under feast/famine conditions as often occur in was tewater treatment processes. The response of microorganisms to such co nditions is the accumulation of storage polymers like poly(beta-hydrox ybutyrate). The research was performed using a pure culture of Paracoc cus pantotrophus LMD 94.21. A steady-state C-limited chemostat culture was switched to batch mode and a pulse of acetate was added. As long as external substrate (acetic acid) was present, the organism grew and accumulated poly(beta-hydroxybutyrate). After depletion of the extern al substrate, the stored poly(beta-hydroxybutyrate) was used as growth substrate. Poly(beta-hydroxybutyrate) accumulation was found to be st rongly dependent on the growth rate of the organism before the pulse a ddition of acetate. Poly(beta-hydroxybutyrate) accumulation was correl ated to the difference in maximum acetate uptake rate and the acetate required for growth. Based on the interpretation of the experimental r esults, a metabolically structured model has been set up. This model a dequately describes the observed kinetics of the poly(beta-hydroxybuty rate) formation and consumption. (C) 1997 John Wiley & Sons, Inc.