Only the fermentations
utilizing whey lactose and whey lactose with pure glycerol
ended at 120 h, reaching maximal propionic acid concentration
of 22.57 g/L and 24.37 g/L, respectively. In the mentioned
variants propionic acid yield (0.56 g/g and 0.63 g/g,
respectively) and productivity (0.18 g/L/h and 0.20 g/L/h,
respectively) were the highest observed in the experiment.
Similar values of propionic acid production (24.80 g/L) and
propionic acid yield (0.60 g/g) were obtained in the fermentation
of whey lactose with crude glycerol, but productivity
was two-fold lower (0.05 g/L/h) in that variant compared
to variants discussed above.