Two internal bottlenecks cause the overflow metabolism leading to poly(3-hydroxybutyrate) production in Azohydromonas lata DSM1123

Polyhydroxybutyrate production in the bacteria Azohydromonas lata DSM1123 has been regarded as growth-associated based on batch experiments. However, growth association can only be confirmed under chemostat culture. In this work, an experimental approach followed by Flux Balance Analysis (FBA) modeling was used to analyze the behavior of this strain under glucose, oxygen, and nitrogen-limited conditions. The model allowed the identification of candidate enzymes constraining the flux through the tricarboxylic acid cycle, and the role of ATP synthase as the key flux controlling enzyme for the respiratory metabolism, in terms of its share of the total metabolically active protein. The results presented in this work and the model developed could assist in the economic and environmental assessment of new continuous processes to produce PHB and other metabolites in A. lata DSM1123, a strain capable of hydrogen use and CO2 fixation.