Effect of culture supplements on metabolic activity of Bifidobacterium animalis subsp. lactis Bb 12 cultivated in skim milk based media

The influence of whey permeate powder and yeast extract concentration as nitrogen source in skim milk based media on growth, β-galactosidase activity and organic acid profile of Bifidobacterium animalis subsp. lactis Bb 12 in batch fermentation was investigated. B. animalis had diauxic growth in these mediums. β- galactosidase activity increased in growth phase and primary stage of stationary phase and then decreased. Increasing in yeast extract concentration increased specific sugar consumption rate and this rising change, was accompanied with reduction in acetic and formic acid formation. These changes were followed by a decrease in molar ratio of acetic acid to lactic acid consequently. When insufficient initial usable nitrogen and adequate carbon source existed in medium, a disorder between growth and organic acid production was observed. In this case specific enzyme synthesis rate is very high in the early hours of fermentation. Succinic acid was produced continuously at growth and stationary phase in all fermentation media. Citric acid could be consumed at stationary phase by this microorganism and its consumption, was extremely correlated with production of succinic acid at this stage (R2= 0.9). Insufficient nitrogen amounts in medium cased shift from anabolism to catabolism for this microorganism. This phenomenon can affect on organoleptic properties of fermented food.