Inhibition of the acidogenic dissimilation of glucose in anaerobic continuous cultures by free butyric acid

In anaerobic wastewater treatment the attainable growth rate of the acidogenic population decreased with increasing influent glucose concentrations. A kinetic model was developed combining substrate and product inhibition. Product inhibition was quantitatively investigated by adding increasing amounts of butyrate (0-200 mmol per litre) and acetate (80, 200 mmol per litre) to a 50.5 mmol glucose per litre solution at pH 5.6-6.6. Only free butyric acid inhibited growth. The decreasing attainable growth rate with increasing amounts of butyrate at pH 5.8 indicated product inhibition. Addition of acetate did not reduce the attainable growth rate.