EFFECT OF AGE OF LACTOBACILLUS-DELBRUECKII SUBSP BULGARICUS CULTURES ON GROWTH OF STREPTOCOCCUS-SALIVARIUS SUBSP THERMOPHILUS

Pure cultures of Lactobacillus delbrueckii subsp. bulgaricus were incubated 4, 8 and 24 h at 43-degrees-C. These cultures served to inoculate milk in addition to fresh cultures of S. thermophilus. Free peptide and amino acid content of the 24 h L. bulgaricus culture was seven times higher than in milk. Cell free fractions of the cultures did not stimulate growth of S. thermophilus. The stimulation of growth of S. thermophilus was not affected by the age of the L. bulgaricus cultures, and there were no significant differences in milk acidification. However, the fermented milks inoculated with the 24 h L. bulgaricus culture showed significantly lower lactobacilli counts as compared to when 4 or 8 h inocula were used.