Antioxidant Peptides from Goat Milk Fermented by Lactobacillus casei L61: Preparation, Optimization, and Stability Evaluation in Simulated Gastrointestinal Fluid

Inhibitory Effects of Fermented Sprouted Oat Extracts on Oxidative Stress and Melanin Overproduction

Hyperpigmentation occurs due to irregular secretion of melanin pigment in the skin. This can affect quality of life depending on its severity, so prevention and management are essential. Oats (Avena sativa L.), a grain consumed worldwide, are known to offer improved health benefits upon germination and fermentation. This study is aimed to investigate the protective effects of lactobacilli-fermented sprouted oat extracts on oxidative stress and melanin overproduction in vitro. The anti-melanogenic effect was investigated using melanin content and tyrosinase activity assays in B16F10 cells, as well as a mushroom tyrosinase-based enzyme inhibition assay. The results showed that L. casei-fermented oat extracts were the most effective for reducing melanin formation by reducing the mRNA expression of microphthalmia-associated transcription factor, tyrosinase, and tyrosinase-related protein 2. Furthermore, L. casei fermentation was effective in improving the total phenolic, flavonoid, and avenanthramide A contents of sprouted oat extracts. The results also demonstrated the antioxidant effects of L. casei-fermented sprouted oat extracts in promoting DPPH radical-scavenging activity, superoxide dismutase-like activity, and reduction in reactive oxygen species levels. Overall, the findings indicate that fermented sprouted oat extracts are promising candidates for antioxidant and anti-hyperpigmentation treatments.

From microbes to molecules: a review of microbial-driven antioxidant peptide generation

Oxidative stress, arising from excess reactive oxygen species (ROS) or insufficient antioxidant defenses, can damage cellular components, such as lipids, proteins, and nucleic acids, resulting in cellular dysfunction. The relationship between oxidative stress and various health disorders has prompted investigations into potent antioxidants that counteract ROS's detrimental impacts. In this context, antioxidant peptides, composed of two to twenty amino acids, have emerged as a unique group of antioxidants and have found applications in food, nutraceuticals, and pharmaceuticals. Antioxidant peptides are sourced from natural ingredients, mainly proteins derived from foods like milk, eggs, meat, fish, and plants. These peptides can be freed from their precursor proteins through enzymatic hydrolysis, fermentation, or gastrointestinal digestion. Previously published studies focused on the origin and production methods of antioxidant peptides, describing their structure-activity relationship and the mechanisms of food-derived antioxidant peptides. Yet, the role of microorganisms hasn't been sufficiently explored, even though the production of antioxidant peptides frequently employs a variety of microorganisms, such as bacteria, fungi, and yeasts, which are recognized for producing specific proteases. This review aims to provide a comprehensive overview of microorganisms and their proteases participating in enzymatic hydrolysis and microbial fermentation to produce antioxidant peptides. This review also covers endogenous peptides originating from microorganisms. The information obtained from this review might guide the discovery of novel organisms adept at generating antioxidant peptides.

Bioactive Ingredients from Dairy-Based Lactic Acid Bacterial Fermentations for Functional Food Production and Their Health Effects

Lactic acid bacteria are traditionally applied in a variety of fermented food products, and they have the ability to produce a wide range of bioactive ingredients during fermentation, including vitamins, bacteriocins, bioactive peptides, and bioactive compounds. The bioactivity and health benefits associated with these ingredients have garnered interest in applications in the functional dairy market and have relevance both as components produced in situ and as functional additives. This review provides a brief description of the regulations regarding the functional food market in the European Union, as well as an overview of some of the functional dairy products currently available in the Irish and European markets. A better understanding of the production of these ingredients excreted by lactic acid bacteria can further drive the development and innovation of the continuously growing functional food market.

Targeted release of soybean peptide from CMC/PVA hydrogels in simulated intestinal fluid and their pharmacokinetics

Carboxymethyl cellulose (CMC)/polyvinyl alcohol (PVA) hydrogels loaded with soybean peptide (SPE) were fabricated via a freeze-thaw method. These hydrogels conquer barriers in simulated gastric fluid (SGF), and then release SPE in simulated intestinal fluid (SIF). The results of in vitro SPE release from these hydrogels showed that in SGF only a little of the SPE released, but in SIF the SPE was completely released. The released SPE had scavenging rates for DPPH and ABTS free radicals of 41.68 and 31.43 %. The pharmacokinetic model of SPE release from the hydrogels in SIF was studied. When the hydrogels are moved from SGF to SIF, the sorption of the shrinkage hydrogel network is entirely controlled by stress-induced relaxations. There are swollen and shrunken regions during SPE release. For SPE release into the SIF, SPE has to be freed from the weak bonds in the swollen regions by changes in the conformation of CMC and PVA. The release rate of SPE was found to be governed by the diffusion and swelling rate of the shrinkage hydrogel network. The Korsmeyer-Peppas equation diffusion exponents (n) for SPE release from the hydrogels are >2.063, indicating a super case II transport. These data demonstrate CMC/PVA hydrogels have potential applications in oral peptide delivery.

Single and Co-Cultures of Proteolytic Lactic Acid Bacteria in the Manufacture of Fermented Milk with High ACE Inhibitory and Antioxidant Activities

In this study, single and co-cultures of proteolytic Lactobacillus delberueckii subsp. bulgaricus ORT2, Limosilactobacillus reuteri SRM2 and Lactococcus lactis subsp. lactis BRM3 isolated from different raw milk samples were applied as starter cultures to manufacture functional fermented milks. Peptide extracts from fermented milk samples were evaluated after fermentation and 7 days of cold storage for proteolytic, angiotensin-converting enzyme (ACE) inhibitory and antioxidant activity by different methods including 2, 2′-diphenyl-1-picrylhydrazyl (DPPH), ferric-reducing antioxidant power (FRAP), OH-radical scavenging, and total antioxidant (molybdate-reducing activity). The highest proteolysis was found in milk fermented by co-cultures of three strains. Fermentation with the mentioned bacteria increased ACE inhibitory and antioxidant activity of the final products which were dependent on peptide concentration. The crude peptide extract obtained from fermented milk with triple co-culture showed the highest ACE inhibitory activity (IC50 = 0.61 mg/mL) which was reduced after 7 days of cold storage (IC50 = 0.78 mg/mL). Similar concentration-dependent activities were found in antioxidant activity at different antioxidant assays. Overall, high proteolytic activity resulted in increased ACE inhibitory and antioxidant activities, but the highest activity was not necessarily found for the samples with the highest proteolytic activity. The results of this study suggest the potential of using co-cultures of L. delberueckii subsp. bulgaricus, L. reuteri and L. lactis subsp. Lactis to manufacture antihypertensive fermented milk.

Peptidomic profiling of fermented goat milk: considering the fermentation-time dependent proteolysis by Lactobacillus and characterization of novel peptides with Antioxidative activity

In this study, antioxidant activities were evaluated for goat milk fermented with Lactobacillus helveticus MTCC 5463. The fermentation conditions (inoculation rate and incubation time) were optimized by estimating proteolytic action of Lactobacillus. SDS-PAGE and 2D gel electrophoresis were carried out for identification of molecular weight and purification of identified peptides. 3 and 10 kDa peptides fractions were obtained through ultrafiltration and also by using RP-HPLC. Then, spots from 2D and fractions from RP-HPLC were also evaluated in RP-LC/MS for identification and characterization of peptides. Identified peptides were matched with online database of goat milk i.e. BLASTp (NCBI) and Protein information resource database (PIR) and subsequently, antioxidant activity of these peptides were also confirmed with BIOPEP database. However, antioxidative peptides from fermented goat milk with Lactobacillus helveticus MTCC 5463 could be produced in developing functional goat milk yoghurt.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-021-05243-w.

Functional bacterial cultures for dairy applications: towards improving safety, quality, nutritional and health benefit aspects

Traditionally, fermentation was used to preserve the shelf life of food. Currently, in addition to favouring food preservation, well standardized and controlled industrial processes are also aimed at improving the functional characteristics of the final product. In this regard, starter cultures have become an essential cornerstone of food production. The selection of robust microorganisms, well adapted to the food environment, has been followed by the development of microbial consortia that provide some functional characteristics, beyond their acidifying capacity, achieving safer, high‐quality foods with improved nutritional and health‐promoting properties. In addition to starters, adjunct cultures and probiotics, which normally do not have a relevant role in fermentation, are added to the food in order to provide some beneficial characteristics. This review focuses on highlighting the functional characteristics of food starters, as well as adjunct and probiotic cultures (mainly lactic acid bacteria and bifidobacteria), with a specific focus on the synthesis of metabolites for preservation and safety aspects (e.g. bacteriocins), organoleptic properties (e.g. exopolysaccharides), nutritional (e.g. vitamins) and health improvement (e.g. neuroactive molecules). Literature reporting the application of these functional cultures in the manufacture of foods, mainly those related to dairy production, such as cheeses and fermented milks, has also been updated.

Antioxidant Activity of Milk and Dairy Products

The aim of the study was to present a review of literature data on the antioxidant potential of raw milk and dairy products (milk, fermented products, and cheese) and the possibility to modify its level at the milk production and processing stage. Based on the available reports, it can be concluded that the consumption of products that are a rich source of bioactive components improves the antioxidant status of the organism and reduces the risk of development of many civilization diseases. Milk and dairy products are undoubtedly rich sources of antioxidant compounds. Various methods, in particular, ABTS, FRAP, and DPPH assays, are used for the measurement of the overall antioxidant activity of milk and dairy products. Research indicates differences in the total antioxidant capacity of milk between animal species, which result from the differences in the chemical compositions of their milk. The content of antioxidant components in milk and the antioxidant potential can be modified through animal nutrition (e.g., supplementation of animal diets with various natural additives (herbal mixtures, waste from fruit and vegetable processing)). The antioxidant potential of dairy products is associated with the quality of the raw material as well as the bacterial cultures and natural plant additives used. Antioxidant peptides released during milk fermentation increase the antioxidant capacity of dairy products, and the use of probiotic strains contributes its enhancement. Investigations have shown that the antioxidant activity of dairy products can be enhanced by the addition of plant raw materials or their extracts in the production process. Natural plant additives should therefore be widely used in animal nutrition or as functional additives to dairy products.

Potential prebiotic properties of exopolysaccharides produced by a novel Lactobacillus strain, Lactobacillus pentosus YY-112

Exopolysaccharides (EPSs) derived from Lactobacilli have important physiological effects and are commonly used as new prebiotics. We identified and studied a new Lactobacillus strain, YY-112, isolated from waxberry (Myrica rubra). This strain, identified as Lactobacillus pentosus, tolerates acids, bile salts, and artificial digestive fluids. The EPS derived from this strain weighed 5.9 × 10⁴ Da and contained glucose, mannose, glucosamine, galactose, and rhamnose at 62.69 : 85.85 : 2.46 : 2.92 : 1.00 molar ratios. We found that the EPS from this strain increased the ratio of Bacteroidetes to Firmicutes and decreased the relative abundance of Proteobacteria, especially Escherichia-Shigella, when added to a simulated gastrointestinal system in vitro. After analysing the short-chain fatty acids, we found that this EPS promoted the production of acetic acid, propionic acid, and butyric acid, and reduced the ratio of acetic acid to propionic acid. We conclude that Lactobacillus pentosus YY-112 is a potential probiotic strain with EPS that is beneficial for the intestinal microbiota and short-chain fatty acid production.

Storage Stability of Antioxidant in Milk Products Fermented with Selected Kefir Grain Microflora

The aim of the study was to assess the antioxidant potential of goat’s milk and whey from goat’s milk fermented with selected bacteria strains from kefir grain (L. plantarum, L. fermentum, L. rhamnosus and L. acidophilus) with regard to fermented cow’s milk with the same bacteria strains. The assessment of antioxidant potential was made by ABTS, DPPH, TPC and FRAP methods. The work also assessed metabolic activity of tested lactic acid bacteria using measurement of electrical impedance changes in the growing medium. The highest values describing the antioxidant potential were found for fermented milk by L. acidophilus. It was also found that the time of cooling storage causes significantly increasing the antioxidant potential of most analyzed samples. Metabolic activity of tested lactic acid bacteria was the highest for cow’s milk. The course of curves for goat’s milk and whey from goat’s milk was similar, which confirms the differences between cow and goat milk.

A comprehensive review on bioactive peptides derived from milk and milk products of minor dairy species

Abstract

Milk from different species has been exploited for the isolation of various functional ingredients for decades. Irrespective of the source, milk is considered as a complete food, as it provides essential nutrients required by the human body. Proteins and their fractions are valuable sources of bioactive peptides that might exert a health beneficial role in the human body such as immune-modulation, antioxidant activity, ACE-inhibitory activity, anti-neoplastic, anti-microbial, etc. In milk, bioactive peptides may either be present in their natural form or released from their parental proteins due to enzymatic action. The increasing interest in bioactive peptides among researchers has lately augmented the exploration of minor dairy species such as sheep, goat, camel, mithun, mare, and donkey. Alternative to cow, milk from minor dairy species have also been proven to be healthier from infancy to older age owing to their higher digestibility and other nutritive components. Therefore, realizing the significance of milk from such species and incentivized interest towards the derivatization of bioactive peptides, the present review highlights the significant research achievements on bioactive peptides from milk and milk products of minor dairy species.

Graphical abstract

Assessment of Microbiological Quality and Physicochemical Parameters of Fruhe Made by Ovine and Goat Milk: A Sardinian (Italy) Cheese

Fruhe (Casu axedu) is a fresh cheese, traditionally manufactured in Sardinia (Italy) from sheep or goat milk, characterized by a compact coagulum obtained from raw or heat-treated whole milk. The objective of this study was to investigate the microbiological quality and physicochemical parameters of the sheep and goat Fruhe types of cheese at 21 days of cold storage. Chemical analyses showed that all Fruhe cheese samples were characterized by a pH below 4.4 and a variable content of total solid (22.75–21.06 g/100 g) proteins (5.4–10 g/100 g) and fat (3.9–15.7 g/100 g). The average residual lactose content was 2.6 g/100 g, while lactic acid content was 1.8 g/100 g. Microbial analyses revealed a high number of Lactic Acid Bacteria for both thermophilic and mesophilic streptococci (9 log CFU/g), and no pathogenic bacteria were found. The content of Free Amino Acids and Free Fatty acids point out that a good activity of rennet and microbial enzymes occurred, although Fruhe cheese is not subject to a ripening process. The present research reports the microbiological and nutritional characteristics of the sheep and goat Fruhe cheese that could represent the basis for further investigations, needful to improve its nutritional quality and to preserve its peculiarities.

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.

Identification of New Peptides from Fermented Milk Showing Antioxidant Properties: Mechanism of Action

Due to their beneficial properties, fermented foods are considered important constituents of the human diet. They also contain bioactive peptides, health-promoting compounds studied for a wide range of effects. In this work, several antioxidant peptides extracted from fermented milk proteins were investigated. First, enriched peptide fractions were purified and analysed for their antioxidant capacity in vitro and in a cellular model. Subsequently, from the most active fractions, 23 peptides were identified by mass spectrometry MS/MS), synthesized and tested. Peptides N-15-M, E-11-F, Q-14-R and A-17-E were selected for their antioxidant effects on Caco-2 cells both in the protection against oxidative stress and inhibition of ROS production. To define their action mechanism, the activation of the Kelch-like ECH-associated protein 1/nuclear factor erythroid 2-related factor 2(Keap1/Nrf2) pathway was studied evaluating the translocation of Nrf2 from cytosol to nucleus. In cells treated with N-15-M, Q-14-R and A-17-E, a higher amount of Nrf2 was found in the nucleus with respect to the control. In addition, the three active peptides, through the activation of Keap1/Nrf2 pathway, led to overexpression and increased activity of antioxidant enzymes. Molecular docking analysis confirmed the potential ability of N-15-M, Q-14-R and A-17-E to bind Keap1, showing their destabilizing effect on Keap1/Nrf2 interaction.

The Effect of Eight Thermal Protectants on the Survival Rate and the Viable Counts of Lactobacillus casei After Heat Treatment in Fermented Goat Milk

In order to improve the survival rate of probiotics and produce probiotic goat milk from fermented goat milk of Lactobacillus casei L61 by spray drying. Spray drying has been applied to large-scale industrial production of milk powder due to its high efficiency and low cost. However, high temperatures in spray drying can result in the loss of large numbers of probiotic.The purpose of this paper is to study the effects of eight thermal protectants including skim milk, sucrose, glucose, β-cyclodextrin, gelatin, maltodextrin, glycerol, trehalose on the survival rate and viable counts of L.casei L61 after heat treatment by the single factor experiment. All protective agents have a positive effect on increasing the survival rate of L.casei L61 (p<0.05). The results indicated that the survival rates of L.casei L61 were up to the maximum of 10.94%, 1.13%, 3.04%, 0.21%, 6.97%, 0.075, 4.71% and 0.29%, while the additions of skim milk, sucrose, glucose, β-cyclodextrin, gelatin, maltodextrin, glycerol, trehalose were 20mg/L, 10%, 7%, 15%, 1.5%, 3%, 8mL/L, 10%, respectively; the viable counts after heat treatment are 19.69, 0.81, 1.78, 0.455, 12.2, 0.12, 2.75, 0.435(×106CFU/mL), respectively. This paper provides technical a reference for the development of probiotic goat milk powder.