Angiotensin I-converting enzyme (ACE) peptides are bioactive peptides that have important value in terms of research and application in the prevention and treatment of hypertension. While widespread literature is concentrated on casein or whey protein for production of ACE-inhibitory peptides, relatively little information is available on selecting the proper proteases to hydrolyze the protein. In this study, skimmed cow and goat milk were hydrolyzed by four commercial proteases, including alkaline protease, trypsin, bromelain, and papain. Angiotensin I-converting enzyme-inhibitory peptides and degree of hydrolysis (DH) of hydrolysates were measured. Moreover, we compared the difference in ACE-inhibitory activity between cow and goat milk. The results indicated that the DH increased with the increase in hydrolysis time. The alkaline protease-treated hydrolysates exhibited the highest DH value and ACE-inhibitory activity. Additionally, the ACE-inhibitory activity of hydrolysates from goat milk was higher than that of cow milk-derived hydrolysates. Therefore, goat milk is a good source to obtain bioactive peptides with ACE-inhibitory activity, as compared with cow milk. A proper enzyme to produce ACE-inhibitory peptides is important for the development of functional milk products and will provide the theoretical basis for industrial production.

Food-originated angiotensin-I-converting enzyme (ACE)-inhibitory peptides to preserve hypertension are widely investigated over the past decade. Our research aims to discovery novel ACE-inhibitory peptides from bovine milk by couple of complex proteases (alcalase and protease). By means of response surface methodology with the conditions of pH 9.01, 61.81 C and 6.5% ratio of enzyme to substrate, the hydrolysis model contributes to best-performing ACE-inhibitory activity of 85.02%. Through the further purification by consequent ultrafiltration, macroporous resin and gel chromatography, fraction G 2-2 is eventually obtained with ACE-inhibitory activity as high as 92.7%. Two novel peptides of VLPVPQ and VAPFPE are identified by Q-Exactive LC-MS/MS. The molecular docking study further suggests that two novel peptides have good combinations of the S1 and S2 active site pockets and Zn(II) of ACE. Our study provides a fitted mathematical model to produce two novel milk-derived ACE-inhibitory peptides, potentially developing the functional foods, especially for hypertension therapy as initial treatment.

Angiotensin I converting enzyme (ACE) inhibitory peptides derived from milk proteins have obvious effect of lowering blood pressure, safe and non-toxic side effects. This study compared four commercial proteases, namely alcalase, flavourzyme, neutral protease and proteinase K for their ACE inhibitory activity in skimmed goat and cow milk and identified the best one with higher ACE inhibitory activity. The degree of hydrolysis (DH) of alcalase and proteinase K were much higher than flavourzyme, neutral protease for both skimmed goat and cow milk. Alcalase was the best enzyme to produce ACE inhibitory peptides from goat milk, with the ACE inhibitory activity 95.31%, while proteinase K was the optimal protease for hydrolyzing cow milk, with 81.28% ACE inhibitory activity. Furthermore, no correlation was obtained between the ACE inhibitory activity and DH for both goat and cow milk.

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Lactobacillus bulgaricus is a common yogurt starter in dairy production. But the viable counts of the bacteria in the productions are relatively low during free-drying and storage which is not good for its commercial production. In order to obtain a medium with high activity and high density for bacterial cultured, the experiments and regression analysis were conducted by.Box-Behnken design in this study, and a model was established to predict the influence of glucose (9- , which was very similar to the predicted value of the model of 3.00×10 9 cfu·mL -1 , indicating that the optimized conditions and models used were feasible and effective. The optimized medium components can improve the viable counts of bacteria which are useful from its application in industrial production.