title: Peptidomic analysis reveals proteolytic activity of kefir microorganisms on bovine milk proteins.
abstract: METHODS
  The microorganisms that make up kefir grains are well known for lactose fermentation, but the extent to which they hydrolyze and consume milk proteins remains poorly understood. Peptidomics technologies were used to examine the proteolytic activity of kefir grains on bovine milk proteins.
  
  
  RESULTS
  Gel electrophoresis revealed substantial digestion of milk proteins by kefir grains, with mass spectrometric analysis showing the release of 609 protein fragments and alteration of the abundance of >1500 peptides that derived from 27 milk proteins. Kefir contained 25 peptides identified from the literature as having biological activity, including those with antihypertensive, antimicrobial, immunomodulatory, opioid and anti-oxidative functions. 16S rRNA and shotgun metagenomic sequencing identified the principle taxa in the culture as Lactobacillus species.
  
  
  CONCLUSIONS
  The model kefir sample contained thousands of protein fragments released in part by kefir microorganisms and in part by native milk proteases.
authors.affiliation: Department of Food Science and Technology, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States; Foods for Health Institute, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States. Electronic address: dcdallas@ucdavis.edu.
authors.forename: David C
authors.initials: DC
authors.lastname: Dallas
authors.affiliation: Department of Food Science and Technology, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States.
authors.forename: Florine
authors.initials: F
authors.lastname: Citerne
authors.affiliation: Department of Food Science and Technology, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States.
authors.forename: Tian
authors.initials: T
authors.lastname: Tian
authors.affiliation: Department of Food Science and Technology, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States.
authors.forename: Vitor L M
authors.initials: VL
authors.lastname: Silva
authors.affiliation: Department of Food Science and Technology, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States.
authors.forename: Karen M
authors.initials: KM
authors.lastname: Kalanetra
authors.affiliation: Department of Food Science and Technology, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States.
authors.forename: Steven A
authors.initials: SA
authors.lastname: Frese
authors.affiliation: Department of Food Science and Technology, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States.
authors.forename: Randall C
authors.initials: RC
authors.lastname: Robinson
authors.affiliation: Department of Food Science and Technology, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States; Foods for Health Institute, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States.
authors.forename: David A
authors.initials: DA
authors.lastname: Mills
authors.affiliation: Department of Food Science and Technology, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States; Foods for Health Institute, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States.
authors.forename: Daniela
authors.initials: D
authors.lastname: Barile
mesh_terms: D000818:Animals; D002417:Cattle; D043302:Cultured Milk Products / Q000737:chemistry / Q000382:microbiology*; D004269:DNA, Bacterial / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D007778:Lactobacillus / Q000235:genetics; D008894:Milk Proteins / Q000737:chemistry*; D059748:Proteolysis / Q000187:drug effects*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial; D008894:Milk Proteins; D012336:RNA, Ribosomal, 16S
keywords: Functional peptide; Kefir; Milk; Peptidomics; Protease