Production of ACE-inhibitory peptides in milk fermented with selected lactic acid bacteria

Abstract

The ability of lactic acid bacteria to release bioactive peptides is strain specific and is dependent of the dairy processing conditions. In the present study we developed a starter for fermented milk with increased proteolytic and peptidolytic activity. The structure and concentration of bioactive peptides are strongly dependent on the strain-specific proteolytic complex. It could be expected that such peptides would be released during the process of manufacture of fermented milk. Among the possible bioactivities of released peptides is the inhibitory effect against angiotensin converting enzyme (ACE), whose increased activity could lead to elevation of the blood pressure. Evaluation of several peptides with proven ACE-inhibitory activity was performed by LC-MS-MS. The structure of these peptides was determined by comparison with peptide library. The quantification of IPP, VPP, and ALPM was performed by SRM MS³ method using certified standards. The ACE inhibitory effect was expressed as the peptide concentration needed to inhibit 50% of ACE activity (IC₅₀). In this study we developed a starter containing L. helveticus, L. bulgaricus, and S. thermophilus strains. The strains L. helveticus A1 and L. bulgaricus J24 possess strong proteolytic complex which lead to increased content of ACE inhibitory peptides. After a pilot production of fermented yoghurt with the developed starter the ACE inhibitory effect was confirmed using enzyme assay. The inclusion of the highly proteolytic strain L. helveticus A1 in the starter culture leads to increased production of bioactive peptides in the fermented milk.