Identification of Angiotensin-I-converting inhibitory peptides in goat milk fermented by lactic acid bacteria isolated from fermented foods and breast milk

In this study, the inhibitory activity of Angiotensin-I-Converting Enzyme (ACEI) was evaluated in fermented goat milk fermented by lactic acid bacteria (LAB) from fermented foods and breast milk. Furthermore, the potential for ACEI peptides was identified of fermented goat milk with the highest ACEI activity. The proteolytic specificity of LAB was also evaluated. The 2% isolate was inoculated into reconstituted goat milk (11% w/v), then incubated at 37 °C until pH 4.6 was reached. The supernatant produced by centrifugation was analyzed for ACEI activity and total peptide. Viable counts of LAB and titratable acidity were also evaluated after fermentation. Peptide identification was carried out using Nano LC/MS/MS, and potential as an ACEI peptide was carried out based on a literature review. The result revealed that ACEI activity was produced in all samples (20.44-60.33%). Fermented goat milk by Lc. lactis ssp lactis BD17 produced the highest ACEI activity (60.33%; IC₅₀ 0.297 ± 0.10 mg/mL) after 48 h incubation, viable counts >8 Log CFU/mL, and peptide content 4.037 ± 0.27/mL. A total of 261 peptides were released, predominantly casein (93%). The proteolytic specificity of Lc. lactis ssp lactis BD17 through cleavage on the amino acid tyrosine, leucine, glutamic acid, and proline. A total of 21 peptides were identified as ACEI peptides. This study showed that one of the isolates from fermented food, namely Lc. lactis ssp lactis BD17, has the potential as a starter culture for the production of fermented goat milk which has functional properties as a source of antihypertensive peptides.