Casein Hydrolysates by Lactobacillus brevis and Lactococcus lactis Proteases: Peptide Profile Discriminates Strain-Dependent Enzyme Specificity

Metabarcoding analysis of the microbiota in flocks naturally infected by Coxiella burnetii: First description of the global microbiota in domestic small ruminants

This study investigates Q fever in sheep and goats, key reservoirs for human infection, by metabarcoding and comparing it with q-PCR and serology. Samples from 26 small ruminants (aborted and normal-delivery) and six males across three Q fever-affected herds were analyzed. In sheep herds, seropositivity was 50 and 80 % respectively, with Coxiella (C.) burnetii shedding detected vaginally in the second herd. In goats, 100 % seropositivity and 90 % C. burnetii detection were observed, with nasal and vaginal samples showing the highest detection rates. Metabarcoding revealed significant differences in alpha diversity, with greater richness in blood and evenness in milk from normal-delivery sheep and higher evenness in faeces from aborted sheep. Beta diversity showed distinct vaginal microbiota in normal-delivery females compared to aborted ones. Firmicutes was the most abundant phylum observed. Dominant genera included: Moraxella (nasal), Mycoplasma (blood), Streptococcus (milk), Ureaplasma (vaginal and preputial), Rikenellaceae RC9 gut group (faeces). Significant differences in bacterial composition, including infertility-linked vaginal pathogens, were found across female groups in all herds in the anatomical locations studied, revealing new species and tropisms. Moreover, taxonomic analysis identified C. burnetii in vaginal, milk and environmental samples. This first report of C. burnetii in the caprine nasal cavity suggests an underestimated tropism that may improve Q fever diagnosis. These findings underscore the need for herd-wide Q fever control measures, including males and normal-delivery females. Our findings contribute to new insights into the pathogen's impact on small ruminant microbiota and a novel approach to studying infectious diseases in this sector.

Biological activities, Peptidomics and in silico analysis of low-fat Cheddar cheese after in vitro digestion: Impact of blending camel and bovine Milk

Cheesemaking with camel milk (CM) presents unique challenges and additional health benefits. This study involved preparing low-fat Cheddar cheese (LFCC) by blending bovine milk (BM) with varying levels of CM. Control cheese was made exclusively with BM. After 180 days of ripening, LFCC samples underwent in vitro digestion to determine antioxidant capacities, α-amylase and α-glucosidase inhibition, and angiotensin-converting enzyme inhibition. The peptide profile of LFCC treatments was analyzed using liquid chromatography-quadrupole-time of flight-mass spectrometry. Antioxidant and biological activities were influenced by BM-CM blends and digestion. At days 120 and 180, the number of αs1-casein-derived peptides increased in all samples except for LFCC made with 15% CM. Generally, 88 peptides exhibited ACE inhibition activity after 120 days of ripening, increasing to 114 by day 180. These findings suggest that ripening time positively affects the health-promoting aspects of functional cheese products.

Exploring the Release of Elastin Peptides Generated from Enzymatic Hydrolysis of Bovine Elastin via Peptide Mapping

To enhance the understanding of enzymatic hydrolysis and to accelerate the discovery of key bioactive peptides within enzymatic products, this research focused on elastin as the substrate and investigated the variations in peptide profiles and the production of key bioactive peptides (those exceeding 5% of the total) and their impacts on the biological activity of the hydrolysates. Through the application of advanced analytical techniques, such as stop-flow two-dimensional liquid chromatography and ultra-high-performance liquid chromatography-tandem mass spectrometry, the research tracks the release and profiles of peptides within elastin hydrolysates (EHs). Despite uniform peptide compositions, significant disparities in peptide concentrations were detected across the hydrolysates, hinting at varying levels of bioactive efficacy. A comprehensive identification process pinpointed 403 peptides within the EHs, with 18 peptides surpassing 5% in theoretical maximum content, signaling their crucial role in the hydrolysate's bioactivity. Of particular interest, certain peptides containing sequences of alanine, valine, and glycine were released in higher quantities, suggesting Alcalase® 2.4L's preference for these residues. The analysis not only confirms the peptides' dose-responsive elastase inhibitory potential but also underscores the nuanced interplay between peptide content, biological function, and their collective synergy. The study sets the stage for future research aimed at refining enzymatic treatments to fully exploit the bioactive properties of elastin.

Unconventional microbial proteases as promising tools for the production of bioactive protein hydrolysates

Enzymatic hydrolysis is the most prominent strategy to release bioactive peptides from different food proteins and protein-rich by-products. Unconventional microbial proteases (UMPs) have gaining increased attention for such purposes, particularly from the 2010s. In this review, we present and discuss aspects related to UMPs production, and their use to obtain bioactive protein hydrolysates. Antioxidant and anti-hypertensive potentials, commonly evaluated through in vitro testing, are mainly reported. The in vivo bioactivities of protein hydrolysates and peptides produced through UMPs action are highlighted. In addition to bioactivities, enzymatic hydrolysis acts by modulating the functional properties of proteins for potential food uses. The compiled literature indicates that UMPs are promising biocatalysts to generate bioactive protein hydrolysates, adding up to commercially available enzymes. From the recent interest on this topic, continuous and in-depth research is needed to advance toward the applicability and commercial utility of both UMPs and obtained hydrolysates.

Exploring the DPP-IV Inhibitory, Antioxidant and Antibacterial Potential of Ovine "Scotta" Hydrolysates

The aim of this work was to valorize the by-product derived from the ricotta cheese process (scotta). In this study, ovine scotta was concentrated by ultrafiltration and then subjected to enzymatic hydrolyses using proteases of both vegetable (4% E:S, 4 h, 50 °C) and animal origin (4% E:S, 4 h, 40 °C). The DPP-IV inhibitory, antioxidant, and antibacterial activities of hydrolysates from bromelain (BSPH) and pancreatin (PSPH) were measured in vitro. Both the obtained hydrolysates showed a significantly higher DPP-IV inhibitory activity compared to the control. In particular, BSPH proved to be more effective than PSPH (IC₅₀ 8.5 ± 0.2 vs. 13 ± 1 mg mL⁻¹). Moreover, BSPH showed the best antioxidant power, while PSPH was more able to produce low-MW peptides. BSPH and PSPH hydrolysates showed a variable but slightly inhibitory effect depending on the species or strain of bacteria tested. BSPH and PSPH samples were separated by gel permeation chromatography (GPC). LC-MS/MS analysis of selected GPC fractions allowed identification of differential peptides. Among the peptides 388 were more abundant in BSPH than in the CTRL groups, 667 were more abundant in the PSPH group compared to CTRL, and 97 and 75 of them contained sequences with a reported biological activity, respectively.

Bioactive peptides from foods: production, function, and application

Bioactive peptides are a class of peptides with special physiological functions and have potential applications in human health and disease prevention. Bioactive peptides have gained much research attention because they affect the cardiovascular, endocrine, immune, and nervous systems. Recent research has reported that bioactive peptides are of great value for physiological function regulation, including antioxidation, anti-hypertension, antithrombosis, antibacterial properties, anti-cancer, anti-inflammation, anti-diabetic, anti-obesity, cholesterol-lowering, immunoregulation, mineral binding and opioid activities. The production of food-derived bioactive peptides is mainly through the hydrolysis of digestive enzymes and proteolytic enzymes or microbial fermentation. The purpose of this review is to introduce the production, function, application, challenges, and prospects of food-derived bioactive peptides.

Effect of ripening time on peptide dynamics and bioactive peptide composition in Tulum cheese

Skin bag Tulum cheeses traditionally produced in the Central Taurus region of Turkey were studied to identify peptide profiles by liquid chromatography-tandem mass spectrometry over 180 d of ripening. After mass spectrometry analysis, 203 peptides were identified: 59 from α_S1-casein (CN), 11 from α_S2-CN, 129 from β-CN, and 4 from κ-CN. Numbers of α_S1- and β-CN-derived peptides increased with increasing number of ripening days due to the dependence of newly formed peptides on proteolysis. However, similar increases were not observed for α_S2- and κ-CN-derived peptides. Most identified peptides consisted of β-CN-derived peptides, followed by α_S1-, α_S2-, and κ-CN-derived peptides. Among these, bioactive peptides were found, including antihypertensive, antibacterial, antioxidant, dipeptidyl peptidase-4 inhibitory, metal chelating, skin regenerating, glucagon-like peptide-1 secretion enhancing, opioid, cathepsin B inhibitory, prolyl endopeptidase inhibitory, immunomodulatory, brain function improving, antiamnesic, antihypercholesterolemic, anti-inflammatory, and anticarcinogenic peptides.

Comparative Peptidomic and Metatranscriptomic Analyses Reveal Improved Gamma-Amino Butyric Acid Production Machinery in Levilactobacillus brevis Strain NPS-QW 145 Cocultured with Streptococcus thermophilus Strain ASCC1275 during Milk Fermentation

The high-gamma-amino butyric acid (GABA)-producing bacterium Levilactobacillus brevis strain NPS-QW 145, along with Streptococcus thermophilus (one of the two starter bacteria used to make yogurt for its proteolytic activity), enhances GABA production in milk. However, a mechanistic understanding of how Levilactobacillus brevis cooperates with S. thermophilus to stimulate GABA production has been lacking. Comparative peptidomic and metatranscriptomic analyses were carried out to unravel the casein and lactose utilization patterns during milk fermentation with the coculture. We found that particular peptides hydrolyzed by S. thermophilus ASCC1275 were transported and biodegraded with peptidase in Lb. brevis 145 to meet the growth needs of the latter. In addition, amino acid synthesis and metabolism in Lb. brevis 145 were activated to further support its growth. Glucose, as a result of lactose hydrolysis by S. thermophilus 1275, but not available lactose in milk, was metabolized as the main carbon source by Lb. brevis 145 for ATP production. In the stationary phase, under acidic conditions due to the accumulation of lactic acid produced by S. thermophilus 1275, the expression of genes involved in pyridoxal phosphate (coenzyme of glutamic acid decarboxylase) metabolism and glutamic acid decarboxylase (Gad) in Lb. brevis 145 was induced for GABA production.SIGNIFICANCE A huge market for GABA-rich milk as a dietary therapy for the management of hypertension is anticipated. The novelty of this work lies in applying peptide profiles supported by metatranscriptomics to elucidate (i) the pattern of casein hydrolysis by S. thermophilus 1275, (ii) the supply of peptides and glucose by S. thermophilus 1275 to Lb. brevis 145, (iii) the transportation of peptides in Lb. brevis and the degradation of peptides by this organism, which was reported to be nonproteolytic, and (iv) GABA production by Lb. brevis 145 under acidic conditions. Based on the widely reported contribution of lactic acid bacteria (LAB) and GABA to human health, the elucidation of interactions between the two groups of bacterial communities in the production of GABA-rich milk is important for promoting the development of functional dairy food and may provide new insight into the development of industrial GABA production.

Predictive Modeling of Angiotensin I-Converting Enzyme Inhibitory Peptides Using Various Machine Learning Approaches

Food-derived angiotensin I-converting enzyme (ACE) inhibitory peptides could potentially be used as safe supportive therapeutic products for high blood pressure. Theoretical approaches are promising methods with the advantage through exploring the relationships between peptide structures and their bioactivities. In this study, peptides with ACE inhibitory activity were collected and curated. Quantitative structure-activity relationship (QSAR) models were developed by using the combination of various machine learning approaches and chemical descriptors. The resultant models have revealed several structure features accounting for the ACE inhibitions. 14 new dipeptides predicted to lower blood pressure by inhibiting ACE were selected. Molecular docking indicated that these dipeptides formed hydrogen bonds with ACE. Five of these dipeptides were synthesized for experimental testing. The QSAR models developed were proofed to design and propose novel ACE inhibitory peptides. Machine learning algorithms and properly selected chemical descriptors can be promising modeling approaches for rational design of natural functional food components.

Hypolipidemic Roles of Casein-Derived Peptides by Regulation of Trans-Intestinal Cholesterol Excretion and Bile Acid Synthesis

Hyperlipidemia, a syndrome characterized by an abnormal elevation of blood lipids, causes chronic lethal metabolic disorders. Although statins are regularly prescribed to patients, an alternative to treat the burden of excessive lipids is required for cholesterol control. In this study, it was found that the treatment of casein hydrolyzed by pepsin and trypsin induced trans-intestinal cholesterol excretion (TICE) through ATP-binding cassette subfamily G members 5 (ABCG5) expression. Next, we analyzed sequences of the peptides responsible for TICE induction, synthesized artificial peptides based on the sequences, and the hypolipidemic effects of the peptide treatments were assessed in both in vitro and in vivo models. We determined that two bioactive peptides contained in casein hydrolysates (SQSKVLPVPQK and HPHPHLSF) induced TICE through the expression of ABCG5 in enterocytes and suppressed hepatic mRNA expression of cytochrome P450 family 7 subfamily A member 1 (CYP7A1) and CYP8B1by ileal FGF19 expression both in an liver X receptor α (LXRα)-mediated manner. In the hyperlipidemic mouse models, the oral administration of peptides reduced serum cholesterol levels through elevation of the ABCG5 expression in proximal intestine and fecal cholesterol secretion. Besides this, peptides induced ileal expression of fibroblast growth factor 15/19 (FGF15/19) and inhibited hepatic bile acid synthesis. We found that the oral treatment of casein-derived bioactive peptides could improve hyperlipidemia by regulating intestinal excretion and hepatic synthesis of cholesterols.

Preparation, Bioavailability, and Mechanism of Emerging Activities of Ile-Pro-Pro and Val-Pro-Pro

Ile-Pro-Pro and Val-Pro-Pro are two most well-known food-derived bioactive peptides, initially identified as inhibitors of angiotensin I-converting enzyme (ACE) from a sample of sour milk. These two peptides were identified in fermented and enzymatic hydrolyzed cow and non-cow (that is, goat, sheep, buffalo, yak, camel, mare, and donkey) milk, as well as sourdough prepared from wheat, rye, and malt. Similar to other bioactive peptides, bioavailability of these peptides is low (about 0.1%), reaching picomolar concentration in human plasma; they showed blood pressure lowering activity in animals and in human, via improved endothelial function, activation of ACE2, and anti-inflammatory property. Emerging bioactivities of these two peptides toward against metabolic syndrome and bone-protection received limited attention, but may open up new applications of these peptides as functional food ingredients. Further studies are warranted to determine the best source as well as to identify novel enzymes (particularly from traditional fermented milk products) to improve the efficiency of production, to characterize possible peptide receptors using a combination of omics technology with molecular methods to understand if these two peptides act as signal-like molecules, to improve their bioavailability, and to explore new applications based on emerging bioactivities.

Insight into subtilisin E-S7 cleavage pattern based on crystal structure and hydrolysates peptide analysis

The X-ray crystallographic structure of the mature form of subtilisin E-S7 (SES7) at 1.90 Å resolution is reported here. Structural comparisons between the previously reported propeptide-subtilisin E complex (1SCJ) and our mature form subtilisin E-S7 (6O44) provide insight into active site adjustments involved in catalysis and specificity. To further investigate the protease substrate selectivity mechanism, we used SES7 to hydrolyze skim milk and analyzed the hydrolysates by LC-MS for peptide identification. The cleavage pattern suggests a high preference for proline at substrate P2 position. The results based on the peptide analysis are consistent with our structural observations, which is instrumental in future protein engineering by rational design. Furthermore, the ACE-inhibitor and NLN-inhibitor activity of the hydrolysates were determined to assess the utility of SES7 for further industrial applications; IC₅₀-ACE = 67 ± 0.92 μg/mL and IC₅₀-NLN = 263 ± 13 μg/mL.

Antihypertensive peptides from whey proteins fermented by lactic acid bacteria

In this study, whey proteins were fermented with 34 lactic acid bacteria for 48 h at 37 °C and their ability to inhibit angiotensin 1-converting enzyme (ACE) activity were compared. All the lactic acid bacteria displayed varying proteolytic abilities in whey. Their fermentates also displayed varying abilities to inhibit ACE in vitro. Seven fermentates showed strong ACE inhibitory abilities between 84.70 ± 0.67 and 52.40 ± 2.1% with IC₅₀ values between 19.78 ± 1.73 and 2.13 ± 0.7 mg/ml. Pediococcus acidilactici SDL1414 showed the strongest ACE inhibitory activity of 84.7 ± 0.67% (IC₅₀ = 19.78 ± 1.73 μg/ml). Mass spectrometry revealed that more than half (57.7%) of the low molecular weight peptides (< 7 kDa) in the P. acidilactici SDL1414 fermented samples were ACE inhibitory peptides. Our results show that P. acidilactici SDL1414 could be used as a starter culture in the dairy industry to develop antihypertensive functional foods for hypertension management.