Propionic acid production from whey by Propionibacterium acidipropionici ATCC 4965 in
combination with Lactococcus lactis TISTR 1401 was studied. It was found that the optimal initial
inoculum size in propionic acid production was 5% Propionibacterium acidipropionici and 5%
Lactococcus lactis by inoculating both cultures in a medium at the same time. Propionic acid
production by batch fermentation conducted in 2 liters fermentor at 30๐
C , 150 rpm. and pH 6.5
produced maximum propionic acid (17.27 g/l in 168 hours). The propionic acid yield and its
productivity were 0.443 (g/g) and 0.103 (g/l.h), respectively and a number of cells increased from
2.90 x 107
to 3.50 x 1010 cfu/ml.