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3D models of ␣ s1 -casein (A), ␣ s2 -casein (B), and  -casein (C) represented as a solid ribbon backbone for defined secondary structures (coiled ribbons represent ␣ -helices, and broad ribbons represent  -sheets). Colored green balls indicate the beginnings and ends of some hydrolyzed regions. Pink areas correspond to hydrolyzed regions and green areas to regions not cleaved by cell wall proteinases of L. helveticus strains in milk. Side chains of phosphorylated serine residues and of cysteine residues are shown as sticks and are colored by atom type (orange, phosphate; gray, carbon; yellow, sulfur). The representations were deduced from the data of Kumosinski et al. (28) for ␣ s1 -casein, Farrell et al. (9) for ␣ s2 -casein, and Kumosinski et al. (29) for  -casein.
Source publication
Lactobacillus helveticus can possess one or two cell envelope proteinases (CEPs), called PrtH2 and PrtH. The aim of this work was to explore the diversity of 15 strains of L. helveticus, isolated from various origins, in terms of their proteolytic activities and specificities on pure caseins or on milk casein micelles. CEP activity differed 14-fold...
Contexts in source publication
Context 1
... of lactobacilli. Only common cleavage sites, such as Phe 52 -Ala 53 , Phe 119 Interpretation of hydrolyzed regions by casein 3D modeling. 3D molecular-modeling representations of the caseins, de- duced from the data of Kumosinski et al. (28) for s1 -casein, Farrell et al. (9) for s2 -casein, and Kumosinski et al. (29) for -casein, are shown in Fig. ...
Context 2
... N-and C-terminal ends of s1 -casein had less secondary structure than the other parts of the molecule and were more susceptible to hydrolysis in milk ( Fig. 4A; the pink areas cor- respond to hydrolyzed regions). In contrast, the carboxyl-ter- minal region of s1 -casein (amino acid residues Ile 136 to Pro 160 ), which exhibits a high degree of hydrophobicity, was not hydrolyzed in milk, probably due to interactions enhancing the pronounced self-association of the casein monomer in aqueous ...
Context 3
... and therefore, this -helix may not be involved in intermolecular interactions (see Fig. S2 in the supplemental material). The interactions between caseins and minerals ap- pear to reduce the level of access, as reflected by a reduction in the level of hydrolysis of the phosphoserine cluster (14) (rep- resented by the phosphate side chain in Fig. 4). A low level of hydrolysis on the phosphorylated region was also observed in purified casein and was considered likely to be due to the presence of calcium in the buffer, which allowed mineral bind- ing and refolding of the s1 ...
Context 4
... s2 -casein (Fig. 4B), the 3D model shown is based on more recently developed and refined model calcula- tions (9). Again, the N-terminal end of the molecule, corre- sponding to a phosphorylated region, was hydrolyzed from either end, and the other phosphorylated region present in the -helix (Glu 50 to Glu 60 ) was weakly accessible. Moreover, the -helix ...
Context 5
... and Sawyer (25) and Kumosinski et al. (29) found that -casein was more unstructured than the s -caseins, as shown on Fig. 4C, rendering this molecule more accessible to cleavage and subsequently more hydrolyzed than the other caseins. The easier access to -casein by CEPs seems to occur whether -casein is in the purified or the assembled state, as in milk. With the exception of strain ITGLH77, the C-terminal end (Leu 140 to Val 162 ) was not hydrolyzed by ...
Context 6
... and subsequently more hydrolyzed than the other caseins. The easier access to -casein by CEPs seems to occur whether -casein is in the purified or the assembled state, as in milk. With the exception of strain ITGLH77, the C-terminal end (Leu 140 to Val 162 ) was not hydrolyzed by strains that possessed only one CEP (PrtH2) (shown in green in Fig. 4C). This region, rich in proline and glutamine, is likely involved in interactions with the other caseins ...
Similar publications
Most of the lactic acid bacteria (LAB) are able to grow in milk mainly due to the activity of a complex and well-developed proteolytic system.
Cell envelope-associated proteinases (CEPs) begin casein hydrolysis and allow for releasing the peptides, enclosed in the structure of
native milk proteins that are essential for growth of Lactobacillus helv...
Citations
... z o.o., Szczecin, Poland) was systematically transferred (2% v/v of inoculum) into fresh MRS broth (BTL, Łódź, Poland) and anaerobically incubated at 37 • C for 18 h. The starter culture used as the inoculum in the fermentation process was prepared according to the method described by Sadat-Mekmene et al. [24], with certain modifications. Briefly, bacterial cell biomass was harvested by centrifugation (8000× g, 10 min, 4 • C; Eppendorf Centrifuge 5415R, GmbH, Hamburg, Germany) after 18 h of incubation. ...
There is a global need to explore alternative protein sources and develop new health-promoting plant-based products. This study aimed to produce beverages from organic seeds of chickpeas and green or red lentils and assess the potential of using L. plantarum 299v to ferment these beverages. Spectrophotometric methods were used to evaluate the ability of the beverages to neutralize 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH•) and chelate Fe2+. Total dietary fiber (including soluble and insoluble fractions) and the protein profiles were compared among the tested legume-derived beverages. The observations were focused on reductions in pH levels, total extract content, dietary fiber, ash, and moisture levels in all the fermented legume products. Fermentation contributed to increased antioxidative activity in all the tested products. The strongest ability to chelate Fe2+ (58.33 ± 2.35%) was noted in non-fermented green lentil products, while green lentil beverages fermented for 72 h exhibited the highest value of free radical scavenging activity (88.44 ± 4.24 DPPH• inhibition %). Chickpea products fermented for 72 h displayed the highest count of viable bacterial cells at 7.0 ± 0.7 × 108 CFU/g, while those fermented for 48 h exhibited the greatest number (2764) of potential biopeptide sequences. These findings highlight the feasibility of using this probiotic strain to enhance the functional properties of legume-based beverages.
... In the perspective of peptide percentage, it is likely that only PrtH2 was expressed in the kefir grains. Compare with the hydrolyzation of purified casein, the number of αs1-casein-derived peptides will drastic decrease when the strains were grown in milk (Sadat-Mekmene et al., 2011b). ...
... However, there were 12 amino acid residues both in P1 position and P1' position exerted inhibition effects on the cleavage. It is reported that the cleavage sites of PrtH2 toward αs2-casein are mainly located at fragment of f97-162 (Sadat-Mekmene et al., 2011b). The detected 5 peptides of this study were mainly located in fragment of f115-207. ...
Introduction
Kefir grains with efficient proteolytic system is an excellent starter culture for the production of bioactive peptides and milk products. This study explores the casein peptides derived from fermented bovine milk by kefir grains using the peptidomics approaches. The angiotensin converting enzyme (ACE) inhibitory activity of these peptides were also investigated.
Methods
After fermentation, peptidomics based on the LC-MS/MS was used to investigate the dynamic profile and the structure specificity of generated peptides. The ACE inhibitory activity of peptides was determined by measuring the amount of hippuric acid (HA) by a spectrophotometer at 228 nm.
Results
The results indicated that the cell envelope proteinases (CEPs) were the P I -/P III -type. A total of 122 peptides were identified. The β-casein was preferentially hydrolyzed by kefir grains, and the main hydrolysis regions were f57-93, f132-160 and f192-209. The αs1-, and κ-casein were also hydrolyzed by a weaker degree. In the process of fermentation, the accumulated peptides increased with the fermentation time. The fermentation products exhibited ACE inhibitory activity, and this bioactivity remained 63% after simulated gastrointestinal (GI) digestion in vitro . Additionally, 14 Pro-containing peptides with ACE inhibitory activity were also identified.
Conclusion
These results provide new insights and evidence to investigate the bioactive milk peptides generated by kefir grains fermentation, as well as a reference for the development of functional foods.
... In general, the lactic acid bacteria are known to possess only one unique CEP. However, the presence of two and four CEPs in Lactobacillus bulgaricus and Lactobacillus helveticus respectively have been reported in the literature (Jensen et al. 2009;Sadat-Mekmene et al. 2011;Stefanitsi et al. 1995). Lactobacillus helveticus is the most proteolytic species of the genus Lactobacillus with the potential to generate diverse bioactive peptides owing to the presence of four CEPs with different specificities (Raveschot et al. 2018). ...
Bioactive peptides are unique, low molecular weight peptide sequences generally consisting of 2–20 amino acid residues. These peptide sequences are inactive within the parent protein but they become physiologically active once released from the native polypeptide sequence via hydrolysis. There are multiple methods for producing bioactive peptides from precursor protein molecules, with microbial fermentation of various dietary matrices indubitably being a novel method to produce peptides with specialized bioactivity. Fermented foods especially fermented dairy products, legumes, cereals, meat and marine life as a source of bioactive peptides have been well documented. These peptides have gained scientific attention owing to their biofunctional attributes. The food-derived bioactive peptides have the potential to serve as valuable ingredients in functional foods and nutraceutical products to promote health. Bioactive peptides are known to possess various health-promoting properties including anti-carcinogenic, anti-hypertensive, anti-microbial, antioxidant, anti-diabetic, and immunomodulatory effects. The COVID-19 pandemic has put the world's health, economy, and social stability in jeopardy. The SARS-CoV-2 infection contributes to severe conditions and higher mortality in COVID-19 patients with comorbidities. The viral infection not only causes severe respiratory infection but also causes malfunctioning of the Renin-Angiotensin system (RAS), resulting in the downregulation of Angiotensin-converting enzyme II(ACE-II) and subsequent accumulation of Angiotensin II. Several synthetic ACE inhibitory medications are being used to minimize the severity of Angiotensin II adverse effects such as hypertension. The growing concern about the side effects associated with these pharmaceuticals has prompted researchers to look for alternatives in the form of foods and nutraceuticals with health-promoting features. Biologically active peptides have the potential to be used as a new-generation pharmaceutical product for various diseases including COVID-19. The multi-functional food-derived peptides could be a promising approach against COVID-19 infection in patients with chronic complications through their therapeutic actions. However, more in vitro and in vivo studies are required to validate their efficacy in enhancing the survivability and viability of COVID-19 patients. Although many peptides have demonstrated their positive effects via biochemical assays, cell culture, and animal models, the translation of these findings into practical application is limited. This might be related to the bioavailability issues, which influence the correlation of in vitro results with in vivo functions of peptides. To exert a health-promoting impact, these peptides need to withstand severe gastrointestinal conditions and the action of digestive enzymes to reach the target site in an active state. Therefore it is critical to thoroughly investigate the gastrointestinal stability and transport of these biopeptides and devise strategies to improve their absorption and bioavailability.
... Previous studies have shown variations in the ability of different L. helveticus strains to hydrolyze milk proteins, especially casein, and the milk fermented by L. helveticus strains with different CEP genotype led to peptide heterogeneity [5]. Sadat-Mekmene et al. [6] found that the hydrolysis kinetics of αs1-casein was enhanced in the presence of L. helveticus strains with both PrtH1 and PrtH2. Skrzypczak et al. [7] showed that L. helveticus strains expressing three CEPs exhibit a greater degree of casein hydrolysis than those expressing one or two CEPs. ...
... In general, αS1-casein was mainly cleaved in regions I, IV, VI, and VIII by three strains, including the N-and C-termini. Sadat-Mekmene et al. [6] showed similar results and proposed that the lack of secondary structure at the N-and C-terminal ends of αS1-casein led to the susceptibility to hydrolysis in these regions. On the other hand, the micellar forms of casein would also influence the accessibility of different regions of caseins to the CEP of the strains. ...
Lactobacillus helveticus is one of the commonly used starter cultures for manufacturing various fermented dairy products. However, only a few studies have explored the cleavage region preference of L. helveticus with different cell envelope proteinase (CEP) genes. In the present study, we profiled the peptide composition of milk samples fermented by three different L. helveticus strains by means of peptidomics to illustrate their different proteolysis patterns. The result revealed that the differences in peptide profiles of milk samples fermented by different L. helveticus strains were mainly a result of variations in the peptide patterns of the casein fractions, which were correlated with CEP genotypes. This was mainly reflected in the extensiveness of the hydrolysis region of αS1-casein and the degree of β-casein hydrolysis. Bioactive peptides were mostly derived from the hydrolysis region common to the three L. helveticus strains, and DQHXN-Q32M42 fermentation resulted in the highest diversity and abundance of bioactive peptides and a significant antihypertensive effect in spontaneous hypertension rats.
... L. helveticus strains with a slowly milkcoagulating phenotype have been previously isolated from undefined starters 53 and Mongolian fermented milk 54 . This phenotype is linked to the loss of plasmids harboring prt genes 53 , loss of aminopeptidases-encoding genes 55 , and deficiency in purine biosynthesis 56 . Gene decay and genome reduction have been frequently documented in microbes inhabiting nutritional rich environments 57 . ...
Natural whey starters (NWS) are undefined bacterial communities produced daily from whey of the previous cheese-making round, by application of high temperature. As a result, in any dairy plant, NWS are continuously evolving, undefined mixtures of several strains and/or species of lactic acid bacteria, whose composition and performance strongly depend on the selective pressure acting during incubation. While NWS is critical to assure consistency to cheese-making process, little is known about the composition, functional features, and plant-to-plant fluctuations. Here, we integrated 16S rRNA metabarcoding and culture-dependent methods to profile bacterial communities of 10 NWS sampled in the production area of Parmigiano Reggiano cheese. 16S rRNA metabarcoding analysis revealed two main NWS community types, namely NWS type-H and NWS type-D. Lactobacillus helveticus was more abundant in NWS type-H, whilst Lactobacillus delbrueckii/St. thermophilus in NWS type-D, respectively. Based on the prediction of metagenome functions, NWS type-H samples were enriched in functional pathways related to galactose catabolism and purine metabolism, while NWS type-D in pathways related to aromatic and branched chain amino acid biosynthesis, which are flavor compound precursors. Culture-dependent approaches revealed low cultivability of individual colonies as axenic cultures and high genetic diversity in the pool of cultivable survivors. Co-culturing experiments showed that fermentative performance decreases by reducing the bacterial complexity of inoculum, suggesting that biotic interactions and cross-feeding relationships could take place in NWS communities, assuring phenotypic robustness. Even though our data cannot directly predict these ecological interactions, this study provides the basis for experiments targeted at understanding how selective regime affects composition, bacterial interaction, and fermentative performance in NWS.
... Partial cut points were found only in the strains for which both proteases of strain ITGLH1 and strain roselle 5088 existed. It was worth noting that no matter how many proteases were present in the strain, two-thirds of the cut point occurred at the C-terminus of the sequence [21], which was consistent with the results of this study. For example, Lb. helveticus CNRZ 303 and CP790 acted on most of the chemical bonds at the C-terminus of β-casein, while CNRZ 32, CNRZ 303 and LHC2 were closer to the N-terminal, and the product characteristics of the different strains lied in the casein co-culture phase; Lb. helveticus CNRZ 32 hydrolyzed the most diverse peptides [22]. ...
... Unlike other types of proteases in lactic acid bacteria, PrtH1 and PrtH2 in Lb. helveticus lacked the anchoring domain at the C-terminus of the CEP's sequence. Some scholars believe that there are at least two other proteases [21,29,30]. In the comparative study of PrtH1 and PrtH2, it was found that 29 strains of Lb. helveticus could be detected for PrtH2, and PrtH was only found in 18 of them. ...
The purpose of this study was to explore the hydrolytic ability of Lactobacillus helveticus CICC 22171 with regard to protein and the expression of enzyme genes during protein utilization. The results revealed that the strain hydrolyzed casein from the C-terminal, reached the maximum level in 6 h, and the number of amino acids in the hydrolyzed peptide was 7–33. The molecular weight was 652.4–3432.74 kDa. Hydrophobic peptides produced by hydrolysis were the source of β-casein bitterness. Leucine and glutamine were the preferred cleavage points after 1 h; tyrosine and tryptophan subsequently increased. The first step of hydrolysis was controlled by PrtP and PrtM genes and coordinated with the action of PrtH1 and PrtH2. The transport system consisted of DtpT, OppB, OppD and OppF. The hydrolytic third step endopeptidase system consisted of the aminopeptidases (PepN, PepC, PepM and PepA), the endopeptidases (PepE, PepF and PepO); the dipeptidases (PepV and PepD), the tripeptidase PepT; the proline peptidases (PepX, PepP, PepQ, PepR and PepI). The expression of CEP genes was significantly different, and the expression level of genes related to the transport system significantly increased from 0 to 1 h. The specificity of the substrate and action site of endopeptidase was abundant.
... Proteolytic activity is a distinctive trait of L. helveticus that significantly contributes to flavor and texture of fermented milk products [38]. Thanks to this ability, L. helveticus has been widely proved to release peptides from milk [39]. However, in this screening assay L. helveticus candidates did not show any relevant proteolytic activity towards WPC. ...
Cheese whey is the principal by-product of cheese making and is perceived as an environmental pollutant. Different technological procedures have been applied to convert whey into value-added products including whey protein concentrate (WPC). In the present study, 2 Lactobacillus helveticus strains and 5 Streptococcus thermophilus strains, isolated from natural whey starter used in Parmigiano Reggiano production, have been evaluated for their capacity to ferment WPC and to release bioactive peptides. WPC fermented with S. thermophilus RBC06 showed the highest antioxidant activity as well as angiotensin-converting enzyme- and dipeptidyl-peptidase-IV-inhibitory activities followed by WPC fermented by S. thermophilus RBC20 and RBN16. An untargeted peptidomics approach was applied to profile the peptides released after WPC fermentation. Several bioactive peptides, mainly angiotensin-converting enzyme inhibitors, were identified and the anti-hypertensive lactotripeptides valine-proline-proline (VPP) and isoleucine-proline-proline (IPP) were quantified. S. thermophilus RBC06 produced the highest amount of VPP (12.80 ± 0.45 mg/L) whereas the highest quantity of IPP (0.56 ± 0.02 mg/L) was detected in WPC fermented with S. thermophilus RBN16. The present study paved the way for the further exploitation of S. thermophilus RBC06 as new bioactive-peptide producer and for the application of WPC hydrolysates as additives for designing whey-based beverages with improved healthy properties.
... L. helveticus strains with a slowly milk-coagulating phenotype have been previously isolated from unde ned starters [52] and Mongolian fermented milk [53]. This phenotype is linked to the loss of plasmids harboring prt genes [52], loss of aminopeptidases-encoding genes [54], and de ciency in purine biosynthesis [55]. Gene decay and genome reduction have been frequently documented in microbes inhabiting nutritional rich environments [56]. ...
Natural whey starters (NWS) are undefined microbial communities produced daily from whey of the previous cheese-making round, by application of high temperature. As a result, in any dairy plant, NWS are continuously evolving, undefined mixtures of several strains and/or species of lactic acid bacteria, whose composition and performance strongly depend on the selective pressure acting during incubation. While NWS is critical to assure consistency to cheese-making process, little is known about the composition, functional features, and plant-to-plant fluctuations. Here, we integrated culture-dependent methods and 16S rRNA metabarcoding to profile microbial communities of 10 NWS sampled in the production area of Parmigiano Reggiano cheese. 16S rRNA metabarcoding analysis revealed two main NWS community types, namely NWS type-H and NWS type-D, with Lactobacillus helveticus being more abundant in NWS type-H and Lactobacillus delbrueckii / St. thermophilus in NWS type-D, respectively. Based on prediction of metagenome functions, NWS type-H samples have enriched functional pathways related to galactose catabolism and purine metabolism, while NWS type-D were enriched in pathways related to aromatic and branched chain amino acid biosynthesis, which are flavor compound precursors. Culture-dependent approaches reveled low cultivability of individual colonies as axenic cultures and high genetic diversity in the pool of cultivable survivors. Co-culturing experiments showed that fermentative performance decreases by reducing the microbial complexity of inoculum, suggesting that complex biotic interactions and cross-feeding relationships take place in NWS communities, assuring phenotypic robustness. Even though our data cannot directly predict these ecological interactions, this study provides the basis for experiments targeted at understanding how selective regime affects NWS composition, microbial interaction, and technological features.
... Most of the LAB possess only one CEP but L. helveticus displays up to four CEPs depending on the strain (20). L. helveticus strains possessing different numbers of CEP genes were previously characterized for their ability to differently hydrolyze in vitro βand α s1 -caseins (21). However, the knowledge is scarce on the expression and the activity of these CEPs under cheese salt and pH conditions. ...
... Three L. helveticus strains were selected for their content in CEP genes according to previous studies (21-23) ( Table 1). They were cultivated at 42 • C for 24 h without shaking in de Man Rogosa and Sharpe broth (MRS, Difco, Fisher scientific, France) (24) or in 10% (wt/vol) reconstituted low heat skim milk powder (21). Three successive precultures were performed with an inoculation level of 1%. ...
... Cells were diluted to OD 650 nm = 10 with the same buffers containing different NaCl concentrations to have final NaCl concentrations of 0, 0.5, 0.75, 1.5, 3, and 4.5% NaCl (w/v). The α s1 -and β-caseins, prepared as described in Sadat-Mekmene et al. (21), were added to each cell suspension at 5 mg.mL −1 final concentrations. Samples were collected after 0.25, 0.5, 1, 2, 3, and 15 h of hydrolysis. ...
Reducing salt intake can mitigate the prevalence of metabolic disorders. In fermented foods such as cheeses, however, salt can impact the activity of desirable and undesirable microorganisms and thus affect their properties. This study aimed to investigate the effect of salt level on Swiss-type cheese ripening. Since proteolysis is a major event in cheese ripening, three strains of Lactobacillus helveticus were selected on the cell-envelope proteinase (CEP) they harbor. Their proteolytic activity on caseins was studied at six salt levels (0–4.5%) at pH 7.5 and 5.2. Swiss-type cheeses were manufactured at regular, increased, and decreased salt concentrations, and characterized for their composition and techno-functional properties. L. helveticus strains possessed and expressed the expected CEPs, as shown by PCR and shaving experiments. The two strains of L. helveticus that possessed at least the CEP PrtH3 showed the greatest proteolytic activity. Casein hydrolysis in vitro was similar or higher at pH 5.2, i.e., cheese pH, compared to pH 7.5, and slightly decreased at the highest salt concentrations (3.0 and 4.4%). Similarly, in ripened cheeses, these L. helveticus strains showed 1.5–2.4 more proteolysis, compared to the cheeses manufactured without L. helveticus. Regarding the salt effect, the 30% salt-reduced cheeses showed the same proteolysis as regular cheeses, while the upper-salted cheeses showed a slight decrease (−14%) of the non-protein fraction. The microbial and biochemical composition remained unchanged in the 30%-reduced cheeses. In contrast, Propionibacterium freudenreichii, used as ripening bacteria in Swiss cheese, grew more slowly in upper-salted (1.14%, w/w) cheeses, which induced concomitant changes in the metabolites they consumed (−40% lactic acid) or produced (fivefold decrease in propionic acid). Some cheese techno-functional properties were slightly decreased by salt reduction, as extrusion (−17%) and oiling off (−4%) compared to regular cheeses. Overall, this study showed that a 30% salt reduction has little impact in the properties of Swiss-type cheeses, and that starters and ripening cultures strains could be chosen to compensate changes induced by salt modifications in Swiss-type and other hard cheeses.
... Besides the different regions preferred by two subspecies, there were common cleavage regions such as (114-128) and (185-199) shared in two subspecies, which generated seven peptides. However, the number of peptides released from αs2-casein was smaller than that from β-casein during milk fermentation, probably due to the fact that αs2-casein possessed more α-helix and was located in the interior of the casein micelle, which limits the accessibility of the CEPs and peptidases [21,22]. ...
... A previous study indicated that different CEPs may have varied preference to the cleavage regions. The cleavage sites of PrtH and PrtH2 on αs2-casein are located in the regions and (97-162) [22]. H-strains with PrtS were able to hydrolyze αs2-casein, and most cleavage sites were confined to the region (159-207) [23]. ...
... Regarding β-casein, as it contains less secondary structure, it may be more accessible to hydrolysis and generate more peptides than the other caseins [22,24,25], which was confirmed by our results. The fermented samples of ssp. ...
Few studies have investigated the peptidomics of fermented milk by Lactobacillus delbrueckii. The aim of the present study was to interpret the peptidomic pattern of the fermented milk by five strains of L. delbrueckii ssp. bulgaricus and ssp. lactis prior to and after the simulated gastrointestinal digestion in vitro. The results indicated variations in the peptidomics among the samples, particularly between the samples of different subspecies. The peptides originating from β-casein were abundant in the samples of ssp. bulgaricus, whereas the peptides derived from αs1-casein and αs2-casein were more likely to dominate in those of ssp. lactis. For β-casein, the strains of ssp. bulgaricus displayed extensive hydrolysis in the regions of (73–97), (100–120), and (130–209), whereas ssp. lactis mainly focused on (160–209). The digestion appears to reduce the variations of the peptidomics profile in general. Among the five strains, L. delbrueckii ssp. bulgaricus DQHXNS8L6 was the most efficient in the generation of bioactive peptides prior to and after digestion. This research provided an approach for evaluating the peptide profile of the strains during fermentation and digestion.
