Proteolytic profiles of yogurt and probiotic bacteria

Proteolytic activity of dairy lactic acid bacteria and probiotics as determinant of growth and in vitro angiotensin-converting enzyme inhibitory activity in fermented milk

“…Endopeptidase and tripeptidase activities of the EE and IE extracts were detected by thin-layer chromatography (TLC) according to the method of Shihata and Shah [39] and Tan and Konings [45] with some modifications. Each reaction mixture contained 60 µL of a 2 mmol·L -1 substrate (Gly-Ala-Tyr, Gly-Leu-Phe and Bradykinin) in 20 mmol·L -1 Tris-HCl pH 7.0 and 20 µL of extract.…”

“…The proteolytic strains of probiotic and yoghurt bacteria were assessed for selected peptidolytic activities using Pro-Ile, LeuTyr, Leu-Gly, Ala-Met, and Ala-His as well as Gly-Ala-Tyr, Gly-Leu-Phe and bradykinin as substrates according to the method of Shihata and Shah [39] and Wohlrab and Bockelmann [50]. The reaction mixture contained 10 µL of enzyme solution, 424 µL of 50 mmol·L -1 Tris-HCl pH 7.5, 50 µL of 22 mmol·L -1 substrate, 25 µL of peroxidase (5 mg·mL -1 in 0.8 mol·L -1 (NH 4 ) 2 SO 4 ), 25 µl of L-amino acid oxidase (2 mg·mL -1 in distilled water) and 25 µL of o-dianisidine (11.5 mmol·L -1 ).…”

“…Milk, although a rich growth medium, contains low concentration of free amino acids and peptides to efficiently support growth of LAB [39,48]. In response to this limitation, LAB have developed a complex system of proteinases and peptidases, which enable them to utilise casein as an additional source of organic nitrogen [41].…”

“…The proteolytic activities of LAB including yoghurt starter bacteria and probiotic organisms have been studied extensively and proteolytic enzymes have been isolated and characterised [22,39,50]. Such an interest has been derived from the importance of proteolytic system of LAB in cheese ripening and rapid growth in milk during fermentation as well as improved survival during storage [12].…”

“…The pre-inocula were prepared by transferring 1% (v/v) of activated culture to 10 mL aliquots of reconstituted skim milk (RSM) supplemented with 2% glucose and 1% yeast extract. [39,50]. The latter was performed to prevent a carryover of milk proteins and their interference with the assay.…”