Quantitative determination of complex carbohydrates in bovine milk and in milk-based infant formulas.

Quantitative determination of all structural families of complex carbohydrate micronutrients was performed on bovine milk samples, milk-based infant formulas, and whey-based manufacturing raw materials. Differences found between formulas depended mainly on their whey: casein ratios. A solvent separation procedure was required for quantitative estimation of the gangliosides and neutral glycolipids within the fat fraction. All infant formulas except one contained slightly more gangliosides than bovine milk. Complex carbohydrates were consistently higher in the nonfat fraction. By gel permeation chromatography, an oligosaccharide subfraction was separated from a glycopeptide one. Oligosaccharide content of infant formulas increased as a function of the whey:casein ratio, and glycopeptides were found only in formulas made with whey components. Neuraminic acids from infant formulas were associated primarily with the glycoprotein fraction, except in hydrolysate-based preparations in which "precipitable" glycoproteins were converted into "soluble" glycopeptides by trypsin treatment. Because whey-based raw materials are very rich in all bovine milk glycoconjugates and oligosaccharides their increased use will result in high contents of these micronutrients in modern formulas.

Inhibition of localized adhesion of enteropathogenic Escherichia coli to HEp-2 cells by immunoglobulin and oligosaccharide fractions of human colostrum and breast milk.

Secretory IgA (sIgA) purified from colostrum and breast milk obtained from 14 women inhibited the localized adherence of an enteropathogenic Escherichia coli (EPEC) to HEp-2 cells. Inhibition decreased as lactation continued even when the concentration of sIgA was maintained constant at 1 mg/ml. sIgA responded to a 94-kDa plasmid-encoded outer membrane protein implicated as the EPEC adherence factor. An oligosaccharide-enriched fraction (OEF) from these samples also inhibited the attachment of this EPEC. Inhibition by OEFs decreased as lactation continued because of a general reduction in oligosaccharide content. Localized adherence of six other EPEC was also inhibited by sIgA and OEF, whereas attachment of isolates with diffuse or aggregative adherence was not inhibited by these fractions. Experiments with purified oligosaccharide fractions revealed that EPEC attach to HEp-2 cells through a carbohydrate-mediated mechanism based on the preferential recognition of fucosylated residues in human milk.

Effect of oligomannoside-type glycopeptides in diarrheal disease of rabbits induced by Escherichia coli strain RDEC-1.

We examined the effects of a soluble receptor-like complex carbohydrate (an oligomannoside-type glycopeptide) on adherence of a type 1 fimbriated rabbit enteropathogen, Escherichia coli strain RDEC-1. Oligomannoside-type glycopeptide, but not a non-glycosylated peptide mixture used as control, inhibited adherence of type 1 fimbriated RDEC-1 to both rabbit ileal brush borders and guinea pig erythrocytes in vitro. In contrast, during RDEC-1 infection of rabbits the receptor-like oligomannoside did not affect the presence and severity of diarrhea, fecal shedding of organisms, luminal colonization by RDEC-1, or enteroadherence of organisms.

Specific and nonspecific inhibition of adhesion of oral actinomyces and streptococci to erythrocytes and polystyrene by caseinoglycopeptide derivatives.

Various caseinoglycopeptide derivatives prepared from mammalian milk were evaluated as inhibitors of hemagglutinations mediated by Actinomyces viscosus Ny1, Streptococcus sanguis OMZ9, and, for comparative purposes, plant lectins from Arachis hypogaea and Bauhinia purpurea. It was found that recognition of the beta-D-galactose-(1----3)-2-acetamido-2-deoxy-D-galactose carbohydrate chain by Actinomyces viscosus Ny1 organisms and Arachis hypogaea and B. purpurea agglutinins had similar structural requirements; in all cases, the desialylated bovine caseinoglycomacropeptide, on which several units of the above mentioned disaccharide are clustered, behaved as the most potent hemagglutination inhibitor. By contrast, none of the preparations tested inhibited erythrocyte agglutination by S. sanguis OMZ9. Thus, the desialylated bovine caseinoglycomacropeptide acts as a potent and specific inhibitor of oral Actinomyces adhesion to cell membranes (a soft surface) and could be used as a probe for the study of recognition mechanisms mediated by Actinomyces galactose-binding lectins. During the present study, both native and desialylated variants of the same bovine glycomacropeptide also totally prevented the adhesion of Actinomyces viscosus Ny1, S. sanguis OMZ9, and S. mutans OMZ176 to polystyrene surfaces. Comparative evaluations of various structurally different compounds gave the following results. Neither mono- nor disaccharides related to caseinoglycopeptide carbohydrates prevented adhesion; highly positively or negatively charged polypeptides and polysaccharides were either not or only moderately active. Besides these glycomacropeptides, an inhibitory activity was also exhibited by other mucin-type glycoproteins carrying short O-linked carbohydrate chains (including bovine submaxillary mucin), polyethylene glycol, and bovine serum albumin. Consequently, caseinoglycopeptide prevention of oral bacterial adhesion to polystyrene tubes (a hard surface) takes place with no species specificity and can be compared to nonspecific inhibition exhibited by various polymers with very different structural characteristics.

Cell structure and starch nature as key determinants of the digestion rate of starch in legume.

The factors responsible for the slow digestibility of starch in leguminous seeds have been studied by examining microscopically the cooked seeds after various treatments and by measuring starch digestion in vitro. Starch in leguminous seeds is entrapped in parenchyma cells and swells only partially during cooking. The alpha-amylase cannot easily penetrate within the gelatinized starch granules due to steric hindrance and the physical nature of the leguminous starch. Disruption of the cells, especially before cooking increases the susceptibility of starch to alpha-amylase digestion.

Inhibition of human digestive enzymes by hydrogenated malto-oligosaccharides.

Maltose, malto-oligosaccharides and their reduced sugar analogues have been tested as substrates and inhibitors of human salivary alpha-amylase and small intestine alpha-glucosidases. - Maltotriose and maltotetraose as well as their reduced analogues inhibited competitively alpha-amylase. Maltitol, maltotriitol and maltotetraitol were not hydrolyzed. - The small intestine maltases hydrolyzed maltitol at a very low rate, but maltotriitol was split almost at the same rate as maltotriose. These three sugars were weak mutual inhibitors. - The small intestine glucoamylase was slightly inhibited by maltotriitol but not by maltitol whereas fungal glucoamylase activity was strongly competitively inhibited by maltitol. This study shows that where the reducing end glucose unit of the malto-oligosaccharides below five glucose units are converted into sorbitol, their inhibitory effect is retained but their capacity of hydrolysis is reduced or disappears.