Releasing angiotensin I-converting enzyme inhibitory (ACE-I) peptides by Yamadazyma spp. in non-fat milk

The objectives of this study were to analyse the impact of both temperature and different isolates on microbial protease production ability and to examine the hypertensive effect of bioactive peptides (BAPs) that inhibit the angiotensin I-converting enzyme released by fermentation of non-fat milk. First, the ability of several Yamadazyma spp. isolates, which were previously isolated and identified from several sources, was screened in terms of the production of proteolytic enzymes at 15 and 25 degrees C. The effect of temperature on proteolysis activity of selected isolates was considerable, and incubation at 25 degrees C was favourable for protease production. Besides, combinations of three different isolates showed remarkable proteolytic activity during the incubation periods of 24, 48 and 72 h. The highest angiotensin I-converting enzyme inhibitory (ACE-I) activity was detected for the combination Yamadazyma spp. BO10 and B514-1, with an inhibition of 92.5%. The partial purification of peptides by ultrafiltration (cut-off 10 kDa) has no crucial impact on ACE-I activity, and further purification might improve their effectiveness. The implications of fermentation with co-culture may have symbiotic potential to increase the antihypertensive effect of the product. Therefore, these results suggest that Yamadazyma spp. may be used to produce functional products or bioactive peptides presenting health-promoting attributes.