The behavior of Bifidobacterium animalis subsp lactis Bb 12 under batch cultivation. after continuous culturing for tip to 12 d. was monitored in skim milk-based media. Previous continuous Culture for longer than 6d affected the physiology of said microorganism. The minimum inhibitory concentrations of lactic and acetic acids increased from 18 to 26g/l. whereas the molar ratio of acetic to lactic acid increased from 0.8 to 1.55. when the previous Continuous culture increased its duration from 1 to 12 d The specific lactose consumption rate decreased from 0 94 to 0 77 g(lactose/gcell dry) (mass/)h within the batch Culture timeframe, this was concomitant with greater amounts of acetic and formic acids, and lower amounts of lactic acid produced. The beta-galactosidase activity increased as continuous culturing tin-e increased. and reached 446 units/ml by 12 d: however. the rate of enzyme synthesis decreased concomitantly Succinic acid was produced during the exponential growth and stationary phases of the batch culture, but the former at exponential growth phase was higher as the continuous culturing time was longer For comparison purposes. batch cultivation of samples taken from continuous cultures by 1 and 12 d was done using a semi-synthetic medium with glucose as carbon source: a pattern similar to that observed when using skim milk-based media was observed.