Metabolic flux analysis of propionic acid biosynthesis with two immobilized cell reactors fermentation by Propionibacterium

The metabolic network of Propionibacterium freudenreichii CCTCC M207015 for propionic acid biosynthesis, with glucose as the sole carbon source, was built based on the stoichiometric balance equations to illustrate the carbon flux distribution of intermediates and metabolites. The propionic acid production with two immobilized cell reactors fermentation was studied by using the metabolic flux analysis method. The results showed that the flux distribution of nodes of glucose 6-phosphate, phosphoenolpyruvate and pyruvate changed after immobilized cells fermentation regulation. Compared with free cells fermentation, the flux of HMP of the two immobilized cells fermentation significantly increased, also with decrease fluxes of acetic acid and lactic acid. The productivity of propionic acid in plant fibrous-bed reactor fermentation increased 242.72% mainly by directly enhancing propionic acid synthesis pathway, while in the multi-point fibrous-bed reactor fermentation it increased 56.80% through the enhancement of succinic acid biosynthetic pathway, and the relevant key enzyme activity and metabolic flux variation had good consistency.