Co-cultures with integrated in situ product removal for lactate-based propionic acid production

Propionic acid (PA) is a valuable organic acid for the food and feed industry, but no bioproduction at industrial scale exists so far. As product inhibition is a major burden for bioprocesses producing organic acids, in situ product removal (ISPR) is desirable. Here, we demonstrate a new strategy to produce PA with a co-culture coupled with ISPR using electrodialysis. Specifically, Bacillus coagulans first produces lactic acid (LA) from sugar(s) and LA is converted to PA using Veillonella criceti. Applying ISPR to the mentioned co-culture, the specific PA yield was increased from 0.35 to 0.39 g g^-1 compared to no ISPR usage. Furthermore, the productivity was increased from 0.63 to 0.7 g L^-1 h^-1 by applying ISPR. Additionally, it was shown that co-consumption of xylose and glucose led to a higher PA productivity of 0.73 g L^-1 h^-1, although PA yield was only increased slightly up to 0.36 g g^-1.