Potential of novel Lactobacillus helveticus strains and their cell wall bound proteases to release physiologically active peptides from milk proteins

The release of angiotensin converting enzyme inhibitory (ACE-I), antioxidant and immunomodulatory peptides from milk proteins by selected Lactobacillus helveticus strains and their crude protease extracts (CPE) was investigated. Reconstituted skim milk (RSM) was incubated with L. helveticus strains or CPE and samples were tested for functionality using a human peripheral blood mononuclear cell model. Milk peptides produced by L. helveticus 474 CPE with ACE-I activity increased significantly after 6 h incubation followed by a significant reduction after 12 h. Peptides formed by CPE of L. helveticus 1188 showed a significantly greater antioxidative capacity than those from other strains. These peptides also differentially stimulated human peripheral blood mononuclear cells with those liberated by L. helveticus 1188 CPE inducing the highest production of interleukin-10, whereas the CPE of L. helveticus 474 formed peptides with significant induction of interferon-γ. These strains might potentially be used in the development of functional fermented food products.