Use of bioassay to assess functional properties of fermented milks

The fermentation of milk with proteolytic starter cultures, such as Enterococcus faecalis (FAIR E-63) and Lactobacillus delb. bulgaricus (LA 2), can generate peptidic compounds from milk proteins with potential immunomodulating and ACE-inhibitory activity implicated in the regulation of blood pressure. The fractions obtained from centrifugation of fermented milks with Centricon Amicon Ultra 15 filters (cut off 5000Da) were used to assess the ACE-inhibitory activity using a rapid enzymatic test. In addition, fraction aliquots were freeze-dried, re-suspended in culture medium and used at different concentrations to assess the immunomodulatory activity by a simple method based on in vitro bovine lymphocyte proliferation. The proliferation of lymphocytes obtained from non-pregnant dry cows was measured by the MTT assay after 48 h of incubation. The immunomodulating effects of the two different strains were analysed by ANOVA (SPSS 14.0). FAIR E-63 showed a greater ACE-inhibitory potency (72%) than LA2 (59%). Both fermented milks inhibited concanavaline-A lymphocyte proliferation and FAIR E-63 was more potent than LA-2. This effect was statistically significant (P<0.05) at low concentrations (5-25 μg/ml).