Purification and characterization of angiotensin-converting enzyme-inhibitory peptides from Nile tilapia (Oreochromis niloticus) skin gelatine produced by an enzymatic membrane reactor

- Collagen was hydrolysed to <1.2 kDa peptides in an enzyme membrane reactor.
- The hydrolysate exhibited ACE-inhibitory activity.
- Novel ACE-inhibitory peptides were identified in active fractions.
- Simulated gastrointestinal digestion decreased the activity somewhat.
- The hydrolysate may be used for functional foods.

In this study, collagen extracted from Tilapia skin was continuously hydrolysed in an enzyme membrane reactor (EMR) mounted with a 1 kDa cut-off membrane, and the hydrolysate was characterised with respect to peptide size, angiotensin I-converting enzyme (ACE)-inhibitory activity, and stability towards simulated gastrointestinal digestion. Furthermore, the hydrolysate was fractionated by successive chromatographic steps to find the most active peptides. The EMR converted the collagen to peptides with molecular mass below 1.1 kDa. The resulting hydrolysate had an ACE-inhibitory activity (IC50) of 1.2 mg/mL, which was slightly reduced by simulated gastrointestinal digestion. Five novel peptides with ACE-inhibitory activity around 0.8 mg mL−1 were identified in the 2 most active fractions by LC-MS2. These results show that the EMR process is useful for conversion of Tilapia skin collagen into low molecular weight ACE-inhibitory peptides that may be applied as ingredients in functional foods against moderate hypertension.