Abstract: The effect of mixed culture of Leuconostoc mesenteroides subsp. dextranicum and Lactococcus lactis subsp. lactis (prot+) was investigated to achieve an optimal production of carbone dioxide. Only the strain of Leuconostoc mesentroides can produce carbon dioxide from lactose and citrate in milk. The influence of the initial concentration ration between the 2 strains on growth, carbon dioxide, L-lactate, acetic acid production and citrate used was displayed. When the initial inoculum of Lactococcus lactis was 2.5 105 cfu mL 1, the growth and evolved CO2 by Leuconostoc mesenteroides (3 107 cfu mL 1) increased. Whereas, high inoculum of Lactococcus lactis induce a decrease of growth and CO2 production by Leuconostoc 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 Leuconostoc mesenteroides.