title: Cell growth and proteolytic activity of Lactobacillus acidophilus, Lactobacillus helveticus, Lactobacillus delbrueckii ssp. bulgaricus, and Streptococcus thermophilus in milk as affected by supplementation with peptide fractions.
abstract: The present investigation examined the effects of supplementation of milk peptide fractions produced by enzymatic hydrolysis on the fermentation of reconstituted skim milk (RSM). Changes in pH, cell growth, proteolytic activity, and angiotensin-converting enzyme (ACE)-inhibitory activity were monitored during fermentation of RSM by pure cultures of Lactobacillus acidophilus, Lactobacillus helveticus, Lactobacillus delbrueckii ssp. bulgaricus, and Streptococcus thermophilus. The study showed that supplementation with peptide fractions of different molecular weights did not significantly affect the bacterial growth in RSM. All bacteria showed an increased proteolytic activity in RSM supplemented with large peptides (>10 kDa), and L. helveticus in general exhibited the highest proteolytic activity among the bacteria studied. The ACE-inhibitory activity was observed to be the maximum in RSM supplemented with larger peptides (>10 kDa) for all bacteria. The results suggest that proteolysis by bacteria leads to increased production of ACE-inhibitory peptides compared to the supplemented peptides produced by enzymatic hydrolysis.
authors.affiliation: Food and Nutritional Science, School of Biological Sciences, The University of Hong Kong , Hong Kong.
authors.forename: Akanksha
authors.initials: A
authors.lastname: Gandhi
authors.forename: Nagendra P
authors.initials: NP
authors.lastname: Shah
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D002364:Caseins / Q000378:metabolism; D005285:Fermentation; D005516:Food Microbiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D006973:Hypertension / Q000188:drug therapy; D007778:Lactobacillus / Q000254:growth & development / Q000378:metabolism; D007779:Lactobacillus acidophilus / Q000254:growth & development / Q000378:metabolism; D048668:Lactobacillus delbrueckii / Q000254:growth & development / Q000378:metabolism; D052198:Lactobacillus helveticus / Q000254:growth & development / Q000378:metabolism; D008892:Milk / Q000378:metabolism / Q000382:microbiology*; D008894:Milk Proteins / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D010455:Peptides / Q000378:metabolism / Q000494:pharmacology; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism; D019936:Probiotics; D059748:Proteolysis; D048249:Streptococcus thermophilus / Q000254:growth & development / Q000378:metabolism; D013820:Thermolysin / Q000378:metabolism
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D002364:Caseins; D008894:Milk Proteins; D010446:Peptide Fragments; D010455:Peptides; C018135:proteose-peptone; D007703:Peptidyl-Dipeptidase A; D013820:Thermolysin
keywords: ACE-inhibitory activity; milk peptides; ultrafiltration