Study On The ACE Inhibitory Ability Of Lactobacillus Delbrueckii QS306 And Physical And Chemical Properties Of Inhibitory Peptides

The changes of growth characteristics, proteolytic ability and angiotensin converting enzyme (ACE) inhibitory activity of Lactobacillus delbrueckii QS306 in reconstituted skim milk (10%wt/wt) were discussed. In addition its proteolytic ability and angiotensin-converting enzyme (ACE) inhibitory activity were investigated by adding growth promoting substances in the reconstituted skim milk medium. The results showed that Lactobacillus delbrueckii QS306 was slow-growing in skim milk, and the titratable acidity, biomass and free amino acid (or oligopeptides) of strain QS306 were reached to highest value of 62.24°T and 9.87(OD410 nm×10) at 37℃ for 3 days, respectively. At the same time, the proteolytic ability was reached to the highest value (556.36 μg mL-1 Tyr). The proteolytic ability of strain QS306 was improved by adding promoting substances in the reconstituted skim milk medium, and the content of oligopeptides (or free amino acid) and ACE inhibitory activity of this strain whan added guanine (50mg/L) were reached to 620.58 (μg mL-1 Tyr) and 68.52%, and improved 24.53% and 25.90% by the control group, respectively. Fermented milk of QS306 was centrifuged, and the supernatant was subjected to gel filtration (Sephadex-G25, 1.0Τ50cm), and the component 7 that showed highest (53.04%) ACE inhibitory activity was subjected to RP-HPLC(C18:4.6Τ250mm). The ACE inhibitory activity of component 12 and 15 were up to 56.27% and 47.46%. After treatment with pepsin and trypsin alone or combined treatment, the ACE inhibitory activity of component 12 was found to remain at 83.86%,91.53% and 88.43% of the original value. The ACE inhibitory activity of this component was completely preserved after heat treatment, and was decreased to 92.66% of the original value after treatment at 100Κ for 20min.