Fermented milks from Enterococcus faecalis TH563 and Lactobacillus delbrueckii subsp. bulgaricus LA2 manifest different degrees of ACE-inhibitory and immunomodulatory activities

Milk proteins are precursors of biologically active components that are released by enzymatic proteolysis. Among the biological activities recognised in milk components, the angiotensin-I converting enzyme (ACE)-inhibitory and immunomodulatory activities are of great interest. In the present work the ACE-inhibitory and immunomodulatory activities were analysed in milks fermented by two bacterial strains isolated from Italian dairy products, Enterococcus faecalis TH563 or Lactobacillus delbrueckii subsp. bulgaricus (L. delb. bulgaricus) LA2. ACE-inhibitory activity was determined by an already established enzymatic method and immunomodulatory activity by the proliferation of bovine peripheral blood lymphocytes (BPBL) taken from nine cows. BPBL were incubated for 48 h with increasing concentrations of peptide fractions (< 5000 g·mol−1) extracted from the two fermented milks. Concanavalin A (conA), a known activator of lymphocyte proliferation, was used as a positive control. Fermentation products from E. faecalis TH563 showed a significantly (P < 0.05) greater ACE-inhibitory activity than that obtained by L. delb. bulgaricus LA2 (69.43 ± 3.12% vs. 60.86 ± 1.01%). The immunomodulatory activity showed a large interanimal variability. Peptide fractions from milk fermented by L. delb. bulgaricus LA2 significantly inhibited BPBL proliferation at concentrations of 5, 25 and 50 μg·mL−1 in the presence of conA (P < 0.01). E. faecalis TH563 did not significantly modify BPBL proliferation at any peptide concentration used. In conclusion, L. delb. bulgaricus LA2-fermented milk showed ACE-inhibitory and immunomodulatory activities, while E. faecalis TH563-fermented milk had high ACE-inhibitory activity, suggesting a possible use of these strains for determining bioactive properties in dairy products.