Streptococcus thermophilus is a major component of dairy starter cultures used for the manufacture of yoghurt and cheese. In this study, b-galactosidase and lactate dehydrogenase activities were measured in Streptococcus thermophilus cells to evaluate the effect of carbon dioxide availability on the homolactic fermentation process .
β-galactosidase(a) and lactate dehydrogenase(b) activities of S. thermophilus wild-type cells (white bars) and A19( Δ ppc; Δ carB) mutant cells (grey bars) grown in enriched CO2or N2 atmosphere.
Our results originally show a direct correlation between the distribution of the HPr phosphorylated isoforms and the measured level of β-galactosidase and lactate dehydrogenase activities (Fig. 1) and its relevance in milk acidification process.