Production of propionate by fed-batch fermentation of Propionibacterium acidipropionici using mixed feed of lactate and glucose

Propionibacterium acidipropionici was grown in a fed-batch culture, fed with glucose or lactate, or mixtures of lactate and glucose. Lactate and glucose were always simultaneously consumed. As co-substrate, glucose modified the propionate:acetate molar ratio (P/A) and increased the fraction of carbon used for biomass production. A P/A of 7.63 was obtained with a lactate:glucose molar ratio of 4; a P/A value of 1.34 was obtained with lactate alone and 1.85 with glucose alone. The fraction of carbon recovered in biomass was 0.09 for glucose, 0.12 for lactate, and 0.21 for a lactate:glucose molar ratio of 4.