Four strains of bifidobacteria (B. bifidum 93, B. infantis ATCC 17 930
, B. longum ATCC 15 707, and B. longum JR) cultivated in MRS broth mod
ified by the addition of cysteine-hydrochloride (0.05 %) were serially
subcultured in unsupplemented cow milk alone or in combination with K
luyveromyces marxianus var. marxianus 269 under aerobic conditions. In
monoculture, bifidobacteria did not multiply after the second subcult
ure. In contrast, in coculture with yeast bifidobacteria reached count
s about 8 log CFU/g even during 15 subcultures. In addition, K. marxia
nus var. marxianus 269 significantly prolonged the survival of bifidob
acteria in milk at 4 degrees C. The most susceptible strains (B. longu
m JR and B. infantis ATCC 17 930) completely lost their viability with
in 5 and 12 d of storage, respectively, while in coculture with yeasts
all bifidobacteria cultures tested survived for at least 40 d. The re
sults could be useful in producing kefir-like fermented milks containi
ng bifidobacteria.