Kinetic studies on poly-3-hydroxybutyrate formation by Ralstonia eutropha in a two-stage continuous culture system

A continuous culture system consisting of two chemostats in series was used to investigate the kinetics of poly-3-hydroxybutyrate (PHB) formation by R alstonia eutropha. The cells of R. eutropha grew under glucose-limited cond itions in the first-stage and accumulated PHB under nitrogen-limited condit ions in the second-stage. The carbon/nitrogen (CIN) ratio in the second fer menter was controlled by feeding the fermenter with a fresh glucose solutio n. The biokineties of R. eutropha in different nutrient conditions were stu died at various steady states by controlling the dilution rates. The cell g rowth, glucose utilization and PHB formation under the nitrogen-rich condit ions followed a Monod model very well. PHB was accumulated substantially un der nitrogen-limited conditions, and the specific PHB synthetic rate was de pendent on CIN molar ratio, which also closely approximated a Monod model. (C) 2001 Elsevier Science Ltd. All rights reserved.