Production rate of propionic acid in fermentation of cheese whey with enzyme inhibitors

Propionic acid is widely used in chemical, food, and pharmaceutical industries as an important intermediate. Currently, almost all propionic acid is manufactured by chemical synthesis. In this research, propionic acid was produced through fermentation of cheese whey lactose by Propionibacterium acidipropionici. To increase propionic acid production and to decrease acetic acid production, enzyme inhibitors, such as calcium‐EGTA and o‐iodosobenzoate, were tested. These enzyme inhibitors, known to inhibit the particular enzymes in the acetic acid production pathway, were expected to divert the metabolic flux to the propionic acid pathway. Even at a low concentration of 0.01 mM, calcium‐EGTA was found to be effective in suppressing the overall cell growth, which resulted in decreasing the production rates of both acids compared to the uninhibited case. However, addition of 0.3 mM of o‐iodosobenzoate successfully resulted in an increase of cell growth and a 2.4‐fold increase in the propionic acid production rate, whereas the acetic acid production rate was reduced to 30% of the control.