Use of Mass Spectrometry to Profile Peptides in Whey Protein Isolate Medium Fermented by Lactobacillus helveticus LH-2 and Lactobacillus acidophilus La-5

Abstract

Peptides in the 3-kDa ultrafiltrate of fermented whey protein isolate (WPI) medium could be responsible for the antivirulence activity of Lactobacillus helveticus LH-2 and Lactobacillus acidophilus La-5 against Salmonella Typhimurium. Non-fermented and fermented media containing 5.6% WPI were fractionated at a 3 kDa cut-off and the filtrate was analyzed by mass spectrometry. The non-fermented WPI medium contained 109 milk derived peptides, which originated from β-casein (52), αs1-casein (22), αs2-casein (10), κ-casein (8), and β-lactoglobulin (17). Most of these peptides were not found in the fermented media, except for 14 peptides from β-casein and one peptide from αs2-casein. Database searches confirmed that 39 out of the 109 peptides had established physiological functions, including angiotensin-converting-enzyme (ACE) inhibitory, antioxidant, antimicrobial, or immunomodulating activity. A total of 75 peptides were found in the LH-2 cell free spent medium (CFSM): 54 from β-casein, 14 from k-casein, 4 from β-lactoglobulin and 3 from αs2-casein. From these peptides, 19 have previously been associated with several categories of bioactivity. For La-5 CFSM, a total of 15 peptides were sequenced: 8 from β-casein, 5 from αs1-casein, 2 from β-lactoglobulin. Only 5 of these have previously been reported as having bioactivity. Many of the peptides remaining in the fermented medium would contain low-affinity residues for oligopeptide binding proteins and higher resistance to peptidase hydrolysis. These properties of the sequenced peptides could explain their accumulation after fermentation despite the active proteolytic enzymes of LH-2 and La-5 strains. Down-regulated expression of hilA and ssrB genes in S. Typhimurium was observed in the presence of La-5 and LH-2 CFSM. Downregulation was not observed for the Salmonella oppA mutant strain exposed to the same CFSM used to treat the S. Typhimurium DT104 wild-type strain. This result suggests the importance of peptide transport by S. Typhimurium for down regulation of virulence genes in Salmonella.

Comprehensive Profiling of the Native and Modified Peptidomes of Raw Bovine Milk and Processed Milk Products

“…As whey permeate is part of sweet whey, the increasing numbers of IF peptides might originate from the dried sweet whey powder added during IF production. Moreover, the peptidome determined from a whey protein isolate (WPI) revealed peptides originating mainly from β- and α S1 -casein, followed by β-lactoglobulin [ 37 ]. Whey proteins are added to IF to increase the ratio of whey proteins to caseins from 20:80 in bovine milk to better resemble the human milk composition with a ratio of approximately 60:40 [ 38 ].…”

Differences and Similarities in the Peptide Profile of Preterm and Term Mother’s Milk, and Preterm and Term Infant Gastric Samples

“…Differences in milk protein digestion are significant beyond the ability to release amino acids for absorption. Milk proteins contain an array of encrypted fragments that are released upon partial proteolysis; these fragments have an array of bioactive functions, including antimicrobial [ 19 ], immunomodulatory [ 20 ], antihypertensive [ 21 ], opioid [ 22 ], and intestinal wound healing [ 23 , 24 ]. Several of these peptides have been identified in human milk samples and infant digesta [ 13 ].…”

The Relationship Between Breast Milk Components and the Infant Gut Microbiota

“…Mucins 1 and 4 are the most studied mucins. Finally, 600 peptides have been recently identified in HM, which have an array of bioactive functions, including antimicrobial activity ( 40 , 41 ).…”