A recombinant Escherichia coli strain harboring the PHB biosynthesis genes from Alcaligenes eutrophus was used to produce poly-beta-hydroxybutyrate (PHB) by pH-stat fed-batch culture. Initial glucose concentration for optimal growth was found to be 20 g/L from a series of flask cultures. A final PHB concentration of 88.8 g/L could be obtained after 42 hrs of cultivation.