Abstract

The effect of mixed culture of Leuconostoc mesenteroîdes subsp. dextranicum and Lactococcus lactis subsp. lactis (prot⁺) was investigated to achieve an optimal production of carbon dioxide. Only the strain of L. mesenteroîdes can produce carbon dioxide from lactose and citrate in milk. The influence of the initial concentration ration between the two strains on growth, carbon dioxide, L-lactate, acetic acid production and citrate used was studied. When the initial inoculum of L. lactis was 2.5 x 10⁵ cfu/ml, the growth and evolved CO₂ by L. mesenteroîdes (3 x 10⁷ cfu/ml) increased, whereas high inoculum of L. lactis induced a decrease of growth and CO₂ production by L. mesenteroides. In mixed culture, CO₂ production continued after growth stopped, a partial uncoupling can be observed between growth and CO₂ production. A shift of acetate production was observed in mixed culture and 25.6 mM was obtained, whereas 30.18 mM was obtained at the same time in pure culture of L. mesenteroîdes.

Key words: Leuconostoc mesenteroîdes, Lactococcus lactis, milk, lactic acid, acetic acid, citric acid, growth kinetics, fermented milk.