The growth and the intracellular biopolymer Poly-B Hydroxybutyrate (PHB) storage kinetics of Alcaligenes eutrophus were studied in a batch cultivation process.N/C ratio was found to both limit and inhibit the growth of the culture. The effect of initial N/C.was studied in the range 0.03-0.4. Maximum was observed at N/C equal to O. 09. A structured mathemat-ical model was proposed. The model parameters were evaluated using the actual batch fermentation data.The model was used to simulate nutrient feeding profiles for enhanced PHB production in a fed-batch fermentation.