The Impact of Fermentation and In Vitro Digestion on the Formation of Angiotensin-I-Converting Enzyme Inhibitory Activity from Pea and Whey Protein

Abstract

Pea and whey protein were fermented by Lactobacillus helveticus and Saccharomyces cerevisiae in monoculture and in combination at 28 and 37 degrees C in order to release angiotensin-I-converting enzyme (ACE) inhibitory peptides. The fermentation products were subjected to in vitro gastrointestinal digestion, and the digests of nonfermented samples served as controls. After fermentation, the ACE inhibitory activity (%) increased by 18 to 30% for all treatments, except for the fermentations of whey protein with Saccharomyces cerevisiae at 28 degrees C, where no significant change was observed. After digestion, however, both fermented and nonfermented samples reached maximum ACE inhibitory activity. The whey digests tended to have lower (50%) inhibitory concentrations (IC50; 0.14 to 0.07 mg/ml), hence, higher ACE inhibitory activity, than the pea digests (0.23 to 0.11 mg/ml). The nonfermented whey protein digest showed the highest ACE inhibitory activity of all. For pea protein, the nonfermented sample had the lowest IC50 value. These results suggest that in vitro gastrointestinal digestion was the predominant factor controlling the formation of ACE inhibitory activity, hence, indicating its importance in the bioavailability of ACE inhibitory peptides.

Antihypertensive Properties of Plant Protein Derived Peptides

“…In addition, 15 min heat treatment effectively increased the ACE-inhibitory activity of the stomach digest [43,131]. Digestion simulating the physiological conditions of pea proteins sufficed to achieve the highest ACE-inhibitory activity with IC50 value of 0.076 mg/ml [132]. Furthermore, it has been suggested that red lentil protein hydrolysates have ACE-inhibitory properties.…”

Whey Proteins as Source of Bioactive Peptides Against Hypertension

“…Several studies have accordingly provided evidence for this realization -as happened with Manchego cheese, as well as with other fermented solutions and infant formulae [100,261,[278][279][280][281]; for instance, a potent antihypertensive peptide was released via gastrointestinal digestion from a precursor with poor ACE-inhibitory activity in vitro [282] -and some peptides possess a remarkable intrinsic stability, whereas others are susceptible to unwanted degradation [136,261,281]; however, whether of any of those options will apply cannot be known in advance.…”

“…One example is YP, the IC50 of which is 720 M; however, it significantly decreases blood pressure between 2 and 8 h after oral administration to SHR [283]. It should be emphasized that in vivo tests of (putatively) promising bioactive peptides should not come into play before careful in vitro models have been checked -as they can provide useful preliminary information on the stability of such peptides upon exposure to the various peptidases and proteinases that they will likely find in the gastrointestinal tract, prior to eventual transport across the intestinal barrier [278][279].…”

“…Results encompassing prior or subsequent hydrolysis of peptides showed that in vitro digestion controls bioavailability of ACE-inhibitor peptides [162,278] Some authors used whey proteins, fermented (or not at all) with L. helveticus and Saccharomyces cerevisiae, and then subjected them to gastrointestinal digestion; they reached a maximum ACE-inhibitory activity, and unfermented samples were the most active. However, some peptides with in vivo antihypertensive activity -as is the sequence KVLPVPQ, and which did not show in vitro ACE-inhibitory activity, could be transformed to active forms via gastrointestinal digestion [282].…”

“…However, the degree of hydrolysis of a given peptide depends not only on its size and nature, but also on the presence of other peptides in its vicinity [272] -which would make it difficult to test the required number of possibilities in a rather limited experimental program. Several in vitro studies were carried out that show the importance of digestion upon formation and degradation of ACEinhibitor peptides [107,272,[278][279][280]284]. In these studies, peptides were subjected to two stages of hydrolysis that mimic digestion in the body.…”