(567ai) Metabolic Engineering of Propionibacterium Acidipropionici for Enhanced Propionic Acid Production

Propionic acid is widely used as a chemical intermediate in various manufacturing processes, and its salts are common food preservatives. Propionic acid is mainly produced via petrochemicals, but recently there is increasing interest in its production by fermentation. Unfortunately, production by fermentation provides low yields due to acetic acid formation as a byproduct, in addition to the inhibitory effect of porpionic acid accumulation. In this study, over-expression of phosphoenol pyruvate carboxylase (PPC) in Propionibacterium acidipropionici was shown to shift the metabolic flux towards the production of propionate at the expense of acetate, resulting in a higher propionic acid yield from sugar fermented. This finding is consistent with previous work with E. coli over-producing succinate, a precursor of propionate. Furthermore, the fermentation carried out in a fibrous-bed bioreactor increased cell tolerance to propionic acid and productivity. The combination of metabolic and process engineering can facilitate the development of a fermentation process for the economic production of propionic acid from sugars and other renewable feedstocks.