RESUMO
An enzyme-based assay in combination with the most probable number (MPN) technique was developed for the enumeration of bifidobacteria. The assay employs the detection of fructose-6-phosphate phosphoketolase (F6PPK) activity as an indicator of the presence of bifidobacteria. The method was validated against viable counts and optimized with respect to selective media in order to quantitatively assess bifidobacteria in dairy products and other probiotic preparations. Several commercial products and homemade fermented milks were analyzed. Counts of bifidobacteria ranged from 10(7) to 10(8) MPN/ml in commercial products and homemade fermented milks. Commercial starters provided by Argentinean industries had between 10(7) and 10(11) MPN/ml. The results obtained in this study suggest that the combination of F6PPK activity determination and the MPN methodology allows an accurate determination of Bifidobacterium in pure cultures, dairy products, and other probiotic preparations.
