Interrelationship of DOC Distribution in Metabolic Network to Growth Yield in Batch Culture

Oxidative assimilation of dissolved organic carbon (DOC) includes the interrelated processes of catabolism and anabolism. It has been demonstrated that energy uncoupling is a dominant characteristic of substrate-sufficient batch culture. However, the interrelationship of DOC distribution between catabolism and anabolism to the observed growth yield (Yobs) has not yet been clear for substrate-sufficient batch cultures. In this study, the DOC distribution between catabolism and anabolism was described using a ratio of the DOC channeled into carbon dioxide (SCO2) to the DOC converted into biomass (Sg). Based on a balanced oxidative reaction of DOC, a SCO2/Sgdependent Yobs model was developed for substrate-sufficient batch culture, and was verified with experimental and literature data. The model showed a reducing trend of growth yield an increasing SCO2/Sg ratio. It appears that the imbalance between catabolism and anabolism induced by substrate excess leads to non-growth-associated DOC consumption, which is responsible for the observed reduction of Yobs under substrate-sufficient conditions.