The growth and sugar utilization by Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus salivarius ssp. thermophilus isolated from market yogurt

Lactobacillus delbrueckii ssp. bulgaricus Yop 12 and Streptococcus salivarius ssp. thermophilus Yop 9 were isolated from a commercial yogurt of Argentina. Significant differences in grow1h response to glucose. galactose. fructose, lactose and sucrose were found among these strains in pure and mixed cultures. The development and sugars utilization by these strains are completely different from those found in Lactobacillus delbrueckii ssp. bulgaricus SSl and Streptococcus salivarius ssp. thermophilus SS2 isolated from another market yogurt of Argentina. In mixed cultures only with glucose as carbon source there is an increase of grow1h. Lactobacillus delbrueckii ssp. bulgaricus Yop 12 is unable to ferment galactose and sucrose in pure culture. When combined with Streptococcus salivarius ssp. thermophilus Yop 9, Lactobacillus delbrueckii ssp. bulgaricus Yop 12 acquires capacity to grow with galactose. In milk cultures there is a stimulation of grow1h of bath microorganisms. In basal medium with lactose we observed a decrease of grow1h in Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus salivarius ssp. thermophilus. In the presence of fructose or sucrose there is an inhibition of grow1h of bath microorganisms in mixed cultures. Sugars concentrations were measured using high pressure Iiquid chromatography.