A kinetic model for energy spilling-associated product formation in substrate-sufficient continuous culture

It has been demonstrated that excess substrate can cause uncoupling between anabolism and catabolism, which leads to energy spilling. However, the Lue deking-Piret equation for product formation does not account for the energy spilling-associated product formation due to substrate excess. Based on th e growth yield and energy uncoupling models proposed earlier, a kinetic mod el describing energy spilling-associated product formation in relation to r esidual substrate concentration was developed for substrate-sufficient cont inuous culture and was further verified with literature data. The parameter s in the proposed model are well defined and have their own physical meanin gs. From this model, the specific productivity of unit energy spilling-asso ciated substrate consumption, and the maximum product yield coefficient, ca n be determined. Results show that the majority of energy spilling-associat ed substrate consumption was converted to carbon dioxide and less than 6% w as fluxed into the metabolites, while it was found that the maximum product yield coefficients varied markedly under different nutrient limitations. T he results from this research can be used to develop the optimized bioproce ss for maximizing valuable product formation.