Kinetic analysis on inhibited growth and poly(3-hydroxybutyrate) formation of Alcaligenes eutrophus on acetate under nutrient-rich conditions

Abstract

Poly(3-hydroxybutyrate) (PHB) plays an important role in enhanced biological phosphorous removal and is a representative biodegradable thermoplastic polyester accumulated in bacteria such as Alcaligenes eutrophus. A kinetic analysis was conducted on the effects of acetate on cell growth and PHB formation under nutrient-rich conditions. The specific growth rate declined with increase in acetate concentration following an exponential function. The use of a high cell concentration, one important factor in acid detoxification, however, could significantly increase the tolerance of A. eutrophus to acetate. The acetate utilization rate was mainly affected by cell growth rate and less by extracellular acetate concentration. In stationary phase with negligible cell growth, the specific rates of acetate utilization and PHB formation based on active biomass (ABM) were 85 mg HAc per g ABM h and 8 mg PHB per g ABM h, respectively. The acetate uptake rate was increased by 10–30% at high acetate concentrations (5–10 g/l), which led to a temporary increase in PHB molecule size. In exponential growth phase, however, the acetate utilization rate reached 160 mg Hac per g ABM h and PHB synthesis about 30 mg PHB per g ABM h.