Isolation of a glycopolypeptide fraction with Lactobacillus bifidus subspecies pennsylvanicus growth-promoting activity from whole human milk casein

Bioactive Peptides in Milk and Dairy Products: A Review

Functionally and physiologically active peptides are produced from several food proteins during gastrointestinal digestion and fermentation of food materials with lactic acid bacteria. Once bioactive peptides (BPs) are liberated, they exhibit a wide variety of physiological functions in the human body such as gastrointestinal, cardiovascular, immune, endocrine, and nervous systems. These functionalities of the peptides in human health and physiology include antihypertensive, antimicrobial, antioxidative, antithrombotic, opioid, anti-appetizing, immunomodulatory and mineral-binding activities.

Most of the bioactivities of milk proteins are latent, being absent or incomplete in the original native protein, but full activities are manifested upon proteolytic digestion to release and activate encrypted bioactive peptides from the original protein. Bioactive peptides have been identified within the amino acid sequences of native milk proteins. Due to their physiological and physico-chemical versatility, milk peptides are regarded as greatly important components for health promoting foods or pharmaceutical applications.

Milk and colostrum of bovine and other dairy species are considered as the most important source of natural bioactive components. Over the past a few decades, major advances and developments have been achieved on the science, technology and commercial applications of bioactive components which are present naturally in the milk. Although the majority of published works are associated with the search of bioactive peptides in bovine milk samples, some of them are involved in the investigation of ovine or caprine milk. The advent of functional foods has been facilitated by increasing scientific knowledge about the metabolic and genomic effects of diet and specific dietary components on human health.

Extensive in vivo human milk peptidomics reveals specific proteolysis yielding protective antimicrobial peptides

Milk is traditionally considered an ideal source of the basic elemental nutrients required by infants. More detailed examination is revealing that milk represents a more functional ensemble of components with benefits to both infants and mothers. A comprehensive peptidomics method was developed and used to analyze human milk yielding an extensive array of protein products present in the fluid. Over 300 milk peptides were identified originating from major and many minor protein components of milk. As expected, the majority of peptides derived from β-casein, however no peptide fragments from the major milk proteins lactoferrin, α-lactalbumin, and secretory immunoglobulin A were identified. Proteolysis in the mammary gland is selective-released peptides were drawn only from specific proteins and typically from only select parts of the parent sequence. A large number of the peptides showed significant sequence overlap with peptides with known antimicrobial or immunomodulatory functions. Antibacterial assays showed the milk peptide mixtures inhibited the growth of Escherichia coli and Staphylococcus aureus . The predigestion of milk proteins and the consequent release of antibacterial peptides may provide a selective advantage through evolution by protecting both the mother's mammary gland and her nursing offspring from infection.

Pretreatment with glycomacropeptide reduces allergen sensitization, alleviates immediate cutaneous hypersensitivity and protects from anaphylaxis

Allergic disorders are characterized by the involvement of allergen-specific immunoglobulin (Ig)E antibodies and T helper type 2 (Th2) cells. The search for new therapies for allergic diseases has been the primary focus of interest for many investigators in recent years. Glycomacropeptide (GMP) is a biologically active component of milk that exhibits a range of immunomodulatory functions. We examined whether oral administration of GMP could affect the development of allergic sensitization and the severity of immediate cutaneous hypersensitivity reactions and of anaphylaxis. Rats treated with or without GMP were ovalbumin (OVA)-sensitized and several indicators of allergy were evaluated. Pretreatment with GMP resulted in reduction of antigen-specific IgE titre in rats when sensitized with OVA. GMP administration also markedly suppressed the proliferative response of splenocytes to antigen and the production of interleukin (IL)-13 by splenocytes of sensitized animals. In addition, GMP pretreatment attenuated the intensity of the immediate cutaneous reaction induced by antigen and protected the sensitized rats from severe anaphylaxis. These data demonstrate, for the first time, that the administration of GMP prevents allergen sensitization and reduces the severity of the early-phase reaction induced by antigen in cutaneous hypersensitivity and in anaphylaxis. GMP may be used as a novel prophylactic agent for the control of allergic diseases.

Advances in the modulation of the microbial ecology of the gut in early infancy

It is now generally accepted that the microbiota of the human gut may influence health and well-being. Lactic acid bacteria are the most important microorganisms associated with these beneficial effects and the elevated bifidobacterial count may be one of the greatest advantages that breastfed infants have over infants fed with milk formulas. Several studies relative to the selective growth stimulation of bifidobacteria, both in vitro and in vivo, are reported in this review. Over the years, diverse human milk components have been identified as the specific factors able to modulate the growth of bifidobacteria. Even if there is a certain agreement that the bifidogenic activity of human milk may be based not on single growth substances, but on a complex set of interacting factors, the present state of knowledge indicates that the use of non-digestible but fermentable carbohydrates may be an easy and reliable method to influence the growth of lactic acid bacteria. In this context, some of the characteristics of the major physiological effects of inulin-type fructans, of galacto-oligosaccharides, but also of lactoferrin, a milk whey protein fraction with purported bifidogenic activity, are briefly examined.

Biological activities of bovine glycomacropeptide

Biological activity of bovine kappa-caseino glycomacropeptide (GMP) has received much attention in recent years. Research has focused on the ability of GMP to bind cholera and Escherichia coli enterotoxins, inhibit bacterial and viral adhesion, suppress gastric secretions, promote bifidobacterial growth and modulate immune system responses. Of these, protection against toxins, bacteria, and viruses and modulation of the immune system are the most promising applications.

Probiotic bacteria: selective enumeration and survival in dairy foods

A number of health benefits have been claimed for probiotic bacteria such as Lactobacillus acidophilus, Bifidobacterium spp., and Lactobacillus casei. Because of the potential health benefits, these organisms are increasingly incorporated into dairy foods. However, studies have shown low viability of probiotics in market preparations. In order to assess viability of probiotic bacteria, it is important to have a working method for selective enumeration of these probiotic bacteria. Viability of probiotic bacteria is important in order to provide health benefits. Viability of probiotic bacteria can be improved by appropriate selection of acid and bile resistant strains, use of oxygen impermeable containers, two-step fermentation, micro-encapsulation, stress adaptation, incorporation of micronutrients such as peptides and amino acids and by sonication of yogurt bacteria. This review will cover selective enumeration and survival of probiotic bacteria in dairy foods.

Oligosaccharides and glycoconjugates in human milk: their role in host defense

Human milk contains an extremely high concentration of complex carbohydrates, especially oligosaccharides, the third most abundant solid constituent of human milk. The value of human milk nutrients to infants is now widely recognized, and a role for the secretory antibodies of human milk in the defense of the infant is generally accepted. However, a function for nonimmunoglobulin milk protective factors, many of them non-nutrients, in providing for the defense of the nursling is only now beginning to be appreciated. Prominent among postulated defense agents are the milk oligosaccharides and glycoconjugates. Their complex carbohydrate structures are thought to be assembled by the same enzymes, the glycosyltransferases, that synthesize the cell surface glycoconjugates often used as receptors by pathogens. Some milk oligosaccharides and glycoconjugates may protect the nursing infant by acting as receptor homologs, inhibiting the binding of enteropathogens to their host receptors. Ongoing research is linking specific carbohydrate structures with protection against specific pathogens. Current information regarding the composition, protective activities, and protective mechanisms of the milk glycolipids, glycoproteins, mucins, glycosaminoglycans, and oligosaccharides is reviewed.

A cell culture model to identify biologically active peptides generated by bacterial hydrolysis of casein

Consumption of fermented dairy foods has been linked to reduced incidence of colon cancer in population groups. Recently, biologically active compounds have been isolated from these products. Bacterial proteinases, produced by dairy starter cultures, generate a variety of peptides from casein. Some of these casein-derived peptides are likely to alter intestinal cell kinetics. Effects on colon cell kinetics because of the presence of casein-derived peptides may be a mechanism through which fermented dairy foods reduce the risk of colon cancer. We have used two intestinal cell lines (IEC-6 cells, derived from normal rat intestine, and Caco-2 cells, derived from human colon adenocarcinoma) to identify casein peptides that affect intestinal cell kinetics. Cell culture media containing casein were inoculated with three commercial starter cultures and incubated for 4, 8, or 24 h. The bacteria-conditioned media were then filter-sterilized and incubated with the intestinal cells for 6 or 24 h. Rates of [3H]thymidine incorporation and cell cycle kinetics determined by flow cytometry were affected by the culture-modified media in both cell lines. The IEC-6 cells tended to reduce, and Caco-2 cells to increase, rates of cell division after exposure to the media. Intestinal cell response varied among the starter cultures. The results support the use of intestinal cell cultures to identify casein peptides generated by dairy starter cultures, which affect intestinal cell kinetics.

Caseins of various origins and biologically active casein peptides and oligosaccharides: structural and physiological aspects

The first part of the present review is focused on structural aspects concerning the so far studied casein fractions of various origins: they are compared to the four classical major bovine caseins (alpha s1-, alpha s2-, beta- and kappa). The calcium-sensitive casein fractions are always phosphorylated whereas kappa-caseins are glycosylated. The study of the casein genes showed that the calcium-sensitive caseins diverged from a common ancestral gene and during the evolution, intergenic and intragenic duplications occurred. The considerable conservation of the phosphorylation sites emphasizes the importance of phosphorylated residues for the function of caseins, i.e. the formation of micelles and the binding of Ca2+. In kappa-caseins all the prosthetic sugar groups are linked by O-glycosidic linkages: their number varies from 0 to 5 in bovine kappa-casein and up to 10 in human kappa-casein. The structures of the known kappa-casein carbohydrate moieties are described. Finally the milk clotting process (interaction kappa-casein/chymosin) is compared to the blood clotting process (interaction fibrinogen/thrombin): a large number of similarities could be noted between both clotting phenomena. The second part of the review is devoted to the study of short casein peptides endowed with various biological activities. Some of them behaved as immunomodulators or casomorphins or angiotensin I converting enzyme inhibitors; others demonstrated an effect on platelet functions. A 'strategic zone' containing immunostimulating and opioid peptides could be located in cow and human beta-caseins. Furthermore bitter peptides, emulsifying peptides, calcium absorption enhancing peptides, chymosin-inhibiting peptides, have also been described and several further properties have been attributed to the kappa-caseinoglycopeptide; two tetrasaccharides isolated from the latter possess blood group activities. In conclusion caseins, the main milk proteins, should not only be considered as a nutriment but as a possible source of biologically active components. If, in the future, some of the discussed active peptides cannot be characterized in vivo, they can all, nevertheless, be synthesized and used either as food additives or in pharmacology.

The effect of metal chelators and other metabolic inhibitors on the growth of Bifidobacterium bifidus var. Pennsylvanicus

Bifidobacterium bifidus var. Pennsylvanicus, a microaerophilic anaerobe, was grown in the presence of several potential growth inhibitors with the aim of defining its growth requirements and metabolic peculiarities. The following had no effect on its growth: citrate, serum transferrin, serum albumin, colchicine, fluoro-acetate, malonate, and rotenone. The following substances inhibited the growth: fluoride, azide, arsenite, 2, 4-dinitrophenol, hemin, hemoglobin, lactoferrin, alpha, alpha'-bipyridyl, and 8-hydroxyquinoline. Ferrous iron was able to negate the inhibition achieved by alpha, alpha'-bipyridyl, and 8-hydroxyquinoline. It is concluded that iron, probably in its ferrous state, is an obligatory nutrient for the microorganism, and that iron-porphyrin system(s) may be essential for the metabolism of this organism. Because the microorganisms contained in addition to iron large quantities of Mn, Zn, and Cu, it is likely that these metalloelements are crucial for the normal growth of the organism. Growth inhibition by fluoride indicates that Mg-dependent enzymes may also be present in the microorganism.