In vitro fermentation of breast milk oligosaccharides by Bifidobacterium infantis and Lactobacillus gasseri

Fecal microbiota composition of breast-fed infants is correlated with human milk oligosaccharides consumed

OBJECTIVES

This study tested the hypothesis that the fecal bacterial genera of breast-fed (BF) and formula-fed (FF) infants differ and that human milk oligosaccharides (HMOs) modulate the microbiota of BF infants.

METHODS

Fecal samples were obtained from BF (n = 16) or FF (n = 6) infants at 3-month postpartum. Human milk samples were collected on the same day when feces were collected. The microbiota was assessed by pyrosequencing of bacterial 16S ribosomal RNA genes. HMOs were measured by high-performance liquid chromatography-chip time-of-flight mass spectrometry.

RESULTS

The overall microbiota of BF differed from that of FF (P = 0.005). Compared with FF, BF had higher relative abundances of Bacteroides, lower proportions of Clostridium XVIII, Lachnospiraceae incertae sedis, Streptococcus, Enterococcus, and Veillonella (P < 0.05). Bifidobacterium predominated in both BF and FF infants, with no difference in abundance between the 2 groups. The most abundant HMOs were lacto-N-tetraose + lacto-N-neotetraose (LNT + LNnT, 22.6%), followed by 2'-fucosyllactose (2'FL, 14.5%) and lacto-N-fucopentaose I (LNFP I, 9.5%). Partial least squares regression of HMO and microbiota showed several infant fecal bacterial genera could be predicted by their mothers' HMO profiles, and the important HMOs for the prediction of bacterial genera were identified by variable importance in the projection scores.

CONCLUSIONS

These results strengthen the established relation between HMO and the infant microbiota and identify statistical means whereby infant bacterial genera can be predicted by milk HMO. Future studies are needed to validate these findings and determine whether the supplementation of formula with defined HMO could selectively modify the gut microbiota.

Preparative scale purification of fucosyl-N-acetylglucosamine disaccharides and their evaluation as potential prebiotics and antiadhesins

Fucosyl-N-acetylglucosamine disaccharides are important core structures that form part of human mucosal and milk glyco-complexes. We have previously shown that AlfB and AlfC α-L-fucosidases from Lactobacillus casei are able to synthesize fucosyl-α-1,3--N-acetylglucosamine (Fuc-α1,3-GlcNAc) and fucosyl-α-1,6-N-acetylglucosamine (Fuc-α1,6-GlcNAc), respectively, in transglycosylation reactions. Here, these reactions were performed in a semipreparative scale, and the produced disaccharides were purified. The maximum yields obtained of Fuc-α1,3-GlcNAc and Fuc-α1,6-GlcNAc were 4.2 and 9.3 g/l, respectively. The purified fucosyl-disaccharides were then analyzed for their prebiotic effect in vitro using strains from the Lactobacillus casei/paracasei/rhamnosus group and from Bifidobacterium species. The results revealed that 6 out of 11 L. casei strains and 2 out of 6 L. rhamnosus strains tested were able to ferment Fuc-α1,3-GlcNAc, and L. casei BL87 and L. rhamnosus BL327 strains were also able to ferment Fuc-α1,6-GlcNAc. DNA hybridization experiments suggested that the metabolism of Fuc-α1,3-GlcNAc in those strains relies in an α-L-fucosidase homologous to AlfB. Bifidobacterium breve and Bibidobacterium pseudocatenolatum species also metabolized Fuc-α1,3-GlcNAc. Notably, L-fucose was excreted from all the Lactobacillus and Bifidobacterium strains fermenting fucosyl-disaccharides, except from strains L. rhamnosus BL358 and BL377, indicating that in these latest strains, L-fucose was catabolized. The fucosyl-disaccharides were also tested for their inhibitory potential of pathogen adhesion to human colon adenocarcinoma epithelial (HT29) cell line. Enteropathogenic Escherichia coli (EPEC) strains isolated from infantile gastroenteritis were used, and the results showed that both fucosyl-disaccharides inhibited adhesion to different extents of certain EPEC strains to HT29 cells in tissue culture.

Beneficial effects of human milk oligosaccharides on gut microbiota

Human milk is the gold standard for nourishment of early infants because it contains a number of bioactive components, such as human milk oligosaccharides (HMOs). The high concentration and structural diversity of HMOs are unique to humans. HMOs are a group of complex and diverse glycans that are resistant to gastrointestinal digestion and reach the infant colon as the first prebiotics. N-acetyl-glucosamine containing oligosaccharides were first identified 50 years ago as the 'bifidus factor', a selective growth substrate for intestinal bifidobacteria, thus providing a conceptual basis for HMO-specific bifidogenic activity. Bifidobacterial species are the main utilisers of HMOs in the gastrointestinal tract and represent the dominant microbiota of breast-fed infants, and they may play an important role in maintaining the general health of newborn children. Oligosaccharides are also known to directly interact with the surface of pathogenic bacteria, and various oligosaccharides in milk are believed to inhibit the binding of pathogens and toxins to host cell receptors. Furthermore, HMOs are thought to contribute to the development of infant intestine and brain. Oligosaccharides currently added to infant formula are structurally different from the oligosaccharides naturally occurring in human milk and, therefore, they are unlikely to mimic some of the structure-specific effects. In this review, we describe how HMOs can modulate gut microbiota. This article summarises information up to date about the relationship between the intestinal microbiota and HMOs, and other possible indirect effects of HMOs on intestinal environment.

Normal growth of infants receiving an infant formula containing Lactobacillus reuteri, galacto-oligosaccharides, and fructo-oligosaccharide: a randomized controlled trial

BACKGROUND

The safety of an infant formula containing a new mixture of the prebiotics galacto-oligosaccharides (GOS) and fructo-oligosaccharide (FOS) and the probiotic Lactobacillus reuteri needs to be evaluated.

METHODS

Healthy term infants in Singapore were randomly assigned (using computer-generated allocation sequences) to receive exclusively an experimental infant formula containing L. reuteri, GOS (5.50 g/L), and FOS (0.36 g/L) or a control formula containing only L. reuteri from enrollment (7-14 days of age) to 4 months of age. The primary objective of this trial was to demonstrate that weight change between birth and 4 months of age in infants fed the experimental formula was not inferior to World Health Organization (WHO) Child Growth standards. The non-inferiority margin was -0.5 standard deviations (SD). The secondary objectives were to compare changes in anthropometric measurements (weight, length, body mass index, and head circumference), digestive tolerance, stool bacterial counts, urinary D- and L- lactate concentrations, and adverse events in the two formula groups.

RESULTS

The intention-to-treat (ITT) population included all randomized infants stratified by gender, (experimental group, N = 68 and control group, N = 72). The per-protocol (PP) population included 61 infants in the experimental and 62 infants in the control groups. The change in weight-for-age z-score between birth and 4 months was +0.93 (95% confidence interval [CI]: +0.63 to +1.23) SD in the experimental group and +0.92 (95% CI: +0.62 to +1.22) SD in the control group in the PP population, indicating non-inferior weight gain in both formulas groups compared with WHO standards. The ITT population had similar results. Liquid stools occurred more frequently in the experimental compared with the control group and median bifidobacteria, lactobacilli, and enterococci counts were higher in the experimental group (p < 0.05). Other secondary outcomes were not significantly different between groups.

CONCLUSIONS

Infant formula containing L. reuteri + GOS/FOS supports normal growth and is safe.

TRIAL REGISTRATION

ClinicalTrial.gov: NCT01010113.

Carbohydrate catabolic diversity of bifidobacteria and lactobacilli of human origin

Because increased proportions of particular commensal bacteria such as bifidobacteria and lactobacilli have been linked to human health through a variety of mechanisms, there is corresponding interest in identifying carbohydrates that promote growth and metabolic activity of these bacteria. We evaluated the ability of 20 carbohydrates, including several commercially available carbohydrates that are sold as prebiotic ingredients, to support growth of 32 human-derived isolates belonging to the genera Bifidobacterium and Lactobacillus, including those isolated from healthy elderly subjects. In general, bifidobacterial strains were shown to display more diverse carbohydrate utilization profiles compared to the tested Lactobacillus species, with several bifidobacterial strains capable of metabolizing xylo-oligosaccharide (XOS), arabinoxylan, maltodextrin, galactan and carbohydrates containing fructo-oligosaccharide (FOS) components. In contrast, maltodextrin, galactan, arabinogalactan and galactomannan did not support robust growth (≥0.8 OD600 nm) of any of the Lactobacillus strains assessed. Carbohydrate fermentation was variable among strains tested of the same species for both genera. This study advances our knowledge of polysaccharide utilization by human gut commensals, and provides information for the rational design of selective prebiotic food ingredients.

Normal Growth of Healthy Infants Born from HIV+ Mothers Fed a Reduced Protein Infant Formula Containing the Prebiotics Galacto-Oligosaccharides and Fructo-Oligosaccharides: A Randomized Controlled Trial

OBJECTIVE

The aim of the current study was to evaluate the safety of a new reduced protein (2.1 g/100 kcal) infant formula containing 4 g/L of 90% galacto-oligosaccharides (GOS) and 10% fructo-oligosaccharides (FOS).

METHODS

Healthy term infants from Brazil were enrolled. Those born to human immunodeficiency virus (HIV)-positive mothers were randomized to a test (n = 65) or control (n = 63) formula group. Infants born to HIV-negative mothers were either exclusively breast-fed (n = 79) or received a mixed diet (breast milk and test formula, n = 65). Between 2 weeks and 4 months of age, infants were exclusively fed according to their assigned group. Anthropometric measurements were taken at baseline, 1, 2, 3, 4, 6, 8, 10, and 12 months. Digestive tolerance was evaluated during the first 4 months. The primary outcome was mean daily weight gain between 2 weeks and 4 months in the test formula and breast-fed groups.

RESULTS

Data from all infants (N = 272) were used in the intention-to-treat (ITT) analysis and data from 230 infants were used in the per-protocol (PP) analysis. The difference in mean daily weight gain between 2 weeks and 4 months in the test formula and breast-fed groups was 1.257 g/day (one-sided 95% confidence interval [CI]: −0.705 to inf, P < 0.001) in the PP analysis, showing that the lower bound of the 95% CI was above the −3.0 g/day non-inferiority margin. Results were similar in the ITT analysis. Symptoms of digestive tolerance and frequency of adverse events were similar in the two groups.

CONCLUSIONS

The formula containing 2.1 g/100 kcal protein and GOS and FOS was safe and tolerated well.

Diet shapes the gut microbiome of pigs during nursing and weaning

BACKGROUND

The newborn mammal is rapidly colonized by a complex microbial community, whose importance for host health is becoming increasingly clear. Understanding the forces that shape the early community, especially during the nursing period, is critical to gain insight into how this consortium of microbes is assembled. Pigs present an attractive model for nursing humans, given physiological and compositional similarity of pig and human milk and the utility of pigs in experimental studies. However, there is a paucity of data examining the gut microbiome in nursing pigs from birth through weaning using modern molecular methods and fewer experimental studies that examine the impact of diet on these microbial communities.

RESULTS

We characterized the fecal microbiome of pigs from birth through 7 weeks of age, during which the animals were transitioned from an exclusive diet of sow milk to a starter diet composed of plant and animal-based components. Microbial communities were clearly distinguishable based on diet, being relatively stable absent dietary changes. Metagenomic sequencing was used to characterize a subset of animals before and after weaning, which identified glycan degradation pathways differing significantly between diets. Predicted enzymes active on milk-derived glycans that are otherwise indigestible to the host animal were enriched in the microbial metagenome of milk-fed animals. In contrast, the bacterial metagenome of weaned animals was enriched in functional pathways involved in plant glycan deconstruction and consumption.

CONCLUSIONS

The gut microbiome in young pigs is dramatically shaped by the composition of dietary glycans, reflected by the different functional capacities of the microbiome before and after weaning.

The impact of the milk glycobiome on the neonate gut microbiota

Human milk is a complete source of nourishment for the infant. Exclusive breastfeeding not only sustains the infant's development but also guides the proliferation of a protective intestinal microbiota. Among the many components of milk that modulate the infant gut microbiota, the milk glycans, which comprise free oligosaccharides, glycoproteins, and glycolipids, are increasingly recognized as drivers of microbiota development and overall gut health. These glycans may display pleiotropic functions, conferring protection against infectious diseases and also acting as prebiotics, selecting for the growth of beneficial intestinal bacteria. The prebiotic effect of milk glycans has direct application to prevention of diseases such as necrotizing enterocolitis, a common and devastating disease of preterm infants. In this article, we review the impact of the human (and bovine) milk glycome on gut health through establishment of a milk-oriented microbiota in the neonate.

Lactobacilli and bifidobacteria in human breast milk: influence of antibiotherapy and other host and clinical factors

OBJECTIVE

The objective of this work was to study the lactobacilli and bifidobacteria population in human milk of healthy women, and to investigate the influence that several factors (including antibioteraphy during pregnancy and lactation, country and date of birth, delivery mode, or infant age) may exert on such population.

METHODS

A total of 160 women living in Germany or Austria provided the breast milk samples. Initially, 66 samples were randomly selected and cultured on MRS-Cys agar plates. Then, the presence of DNA from the genera Lactobacillus and Bifidobacterium, and from most of the Lactobacillus and Bifidobacterium species that were isolated, was assessed by qualitative polymerase chain reaction (PCR) using genus- and species-specific primers.

RESULTS

Lactobacilli and bifidobacteria could be isolated from the milk of 27 (40.91%) and 7 (10.61%), respectively, of the 66 cultured samples. On the contrary, Lactobacillus and Bifidobacterium sequences were detected by PCR in 108 (67.50%) and 41 (25.62%), respectively, of the 160 samples analyzed. The Lactobacillus species most frequently isolated and detected was L salivarius (35.00%), followed by L fermentum (25.00%) and L gasseri (21.88%), whereas B breve (13.75%) was the bifidobacterial species most commonly recovered and whose DNA was most regularly found. The number of lactobacilli- or bifidobacteria-positive samples was significantly lower in women who had received antibiotherapy during pregnancy or lactation.

CONCLUSIONS

Our results suggest that either the presence of lactobacilli and/or bifidobacteria or their DNA may constitute good markers of a healthy human milk microbiota that has not been altered by the use of antibiotics.

Hydrolysis of milk gangliosides by infant-gut associated bifidobacteria determined by microfluidic chips and high-resolution mass spectrometry

Gangliosides are receiving considerable attention because they participate in diverse biological processes. Milk gangliosides appear to block pathogen adhesion and modify the intestinal ecology of newborns. However, the interaction of milk gangliosides with gut bifidobacteria has been little investigated. The digestion products of a mixture of gangliosides isolated from milk following incubation with six strains of bifidobacteria were studied using nanoHPLC Chip Q-TOF MS. To understand ganglioside catabolism in vitro, the two major milk gangliosides--GM3 and GD3--remaining in the media after incubation with bifidobacteria were quantified. Individual gangliosides were identified through postprocessing precursor ion scans, and quantitated with the "find by molecular feature" algorithm of MassHunter Qualitative Analysis software. Bifidobacterium infantis and B. bifidum substantially degraded the GM3 and GD3, whereas B. longum subsp. longum and B. animalis subsp. lactis only showed moderate degradation. MALDI FTICR MS analysis enabled a deeper investigation of the degradation and identified ganglioside degradation specifically at the outer portions of the glycan molecules. These results indicate that certain infant gut-associated bifidobacteria have the ability to degrade milk gangliosides releasing sialic acid, and that these glycolipids could play a prebiotic role in the infant gut.

Breast milk oligosaccharides: structure-function relationships in the neonate

In addition to providing complete postnatal nutrition, breast milk is a complex biofluid that delivers bioactive components for the growth and development of the intestinal and immune systems. Lactation is a unique opportunity to understand the role of diet in shaping the intestinal environment including the infant microbiome. Of considerable interest is the diversity and abundance of milk glycans that are energetically costly for the mammary gland to produce yet indigestible by infants. Milk glycans comprise free oligosaccharides, glycoproteins, glycopeptides, and glycolipids. Emerging technological advances are enabling more comprehensive, sensitive, and rapid analyses of these different classes of milk glycans. Understanding the impact of inter- and intraindividual glycan diversity on function is an important step toward interventions aimed at improving health and preventing disease. This review discusses the state of technology for glycan analysis and how specific structure-function knowledge is enhancing our understanding of early nutrition in the neonate.

Novel high-molecular weight fucosylated milk oligosaccharides identified in dairy streams

Oligosaccharides are the third largest component in human milk. This abundance is remarkable because oligosaccharides are not digestible by the newborn, and yet they have been conserved and amplified during evolution. In addition to encouraging the growth of a protective microbiota dominated by bifidobacteria, oligosaccharides have anti-infective activity, preventing pathogens from binding to intestinal cells. Although it would be advantageous adding these valuable molecules to infant milk formula, the technologies to reproduce the variety and complexity of human milk oligosaccharides by enzymatic/organic synthesis are not yet mature. Consequently, there is an enormous interest in alternative sources of these valuable oligosaccharides. Recent research has demonstrated that bovine milk and whey permeate also contain oligosaccharides. Thus, a thorough characterization of oligosaccharides in bovine dairy streams is an important step towards fully assessing their specific functionalities. In this study, bovine milk oligosaccharides (BMOs) were concentrated by membrane filtration from a readily available dairy stream called “mother liquor”, and analyzed by high accuracy MALDI FT-ICR mass spectrometry. The combination of HPLC and accurate mass spectrometry allowed the identification of ideal processing conditions leading to the production of Kg amount of BMO enriched powders. Among the BMOs identified, 18 have high-molecular weight and corresponded in size to the most abundant oligosaccharides present in human milk. Notably 6 oligosaccharides contained fucose, a sugar monomer that is highly abundant in human milk, but is rarely observed in bovine milk. This work shows that dairy streams represent a potential source of complex milk oligosaccharides for commercial development of unique dairy ingredients in functional foods that reproduce the benefits of human milk.

The marriage of nutrigenomics with the microbiome: the case of infant-associated bifidobacteria and milk

Broadly, nutrigenomics examines the association of exogenous nutrients and molecular responses to maintain homeostasis in an individual. Phenotypic expression profiling, often transcriptomics, has been applied to identify markers and metabolic consequences of suboptimal diet, lifestyle, or both. The decade after the Human Genome Project has been marked with advances in high-throughput analysis of biological polymers and metabolites, prompting a rapid increase in characterization of the profound nature by which our symbiotic microbiota influences human physiology. Although the technology is widely accessible to assess microbiome composition, genetic potential, and global function, nutrigenomics studies often exclude the microbial contribution to host responses to ingested nutritive molecules. Perhaps a hallmark of coevolution, milk provides a dramatic example of a diet that promotes a particular microbial community structure, because the lower infant gastrointestinal tract is often dominated by bifidobacteria that flourish on milk glycans. Systems-level approaches should continue to be applied to examine the microbial communities in the context of their host's dietary habits and metabolic status. In addition, studies of isolated microbiota species should be encouraged to inform clinical studies and interventions as well as community studies. Whereas nutrigenomics research is beginning to account for resident microbiota, the need remains to consistently consider our microscopic partners in the human holobiont.

Isomer-specific consumption of galactooligosaccharides by bifidobacterial species

Prebiotics are nondigestible substrates that stimulate the growth of beneficial microbes in the human intestine. Galactooligosaccharides (GOS) are food ingredients that possess prebiotic properties, in particular, promoting the growth of bifidobacteria in situ. However, precise mechanistic details of GOS consumption by bifidobacteria remain poorly understood. Because GOS are mixtures of polymers of different lengths and linkages, there is interest in determining which specific structures provide prebiotic effects to potentially create better supplements. This paper presents a method comprising porous graphitic carbon separation, isotopic labeling, and mass spectrometry analysis for the structure-specific analysis of GOS isomers and their bacterial consumption rate. Using this strategy, the differential bacterial consumption of GOS by the bifidobacteria species Bifidobacterium longum subsp. infantis, Bifidobacterium animalis subsp. lactis, and Bifidobacterium adolescentis was determined, indicating that the use of specific GOS isomers in infant formula may provide enrichment of distinct species.

Maternal regulation of offspring development in mammals is an ancient adaptation tied to lactation

The developmental origins of health and disease (DOHaD) is a paradigm for understanding metabolic diseases of modern humans. Vulnerability to disease is linked to perturbations in development during critical time periods in fetal and neonatal life. These perturbations are caused by environmental signals, often generated or transduced by the mother. The regulation of mammalian development depends to a large extent on maternal biochemical signals to her offspring. We argue that this adaptation is ancient, and originated with the evolution of lactation. Lactation evolved earlier than live birth and before the extensive placental development of modern eutherian mammals. Milk contains a host of signaling molecules including nutrients, immunoglobulins, growth factors and metabolic hormones. As evidenced by marsupials, lactation originally served to supply the biochemical factors for growth and development for what is essentially a fetus to a weanling transitioning to independent existence. In placental mammals maternal signaling in earliest life is accomplished through the maternal-placental-fetal connection, with more of development shifted to in utero life. However, significant development occurs postpartum, supported by milk. Mothers of all taxa provide biochemical signals to their offspring, but for non-mammalian mothers the time window is short. Developing mammals receive maternal biochemical signals over an extended period. These signals serve to guide normal development, but also can vary in response to environmental conditions. The ancient adaptation of lactation resulted in a lineage (mammals) in which maternal regulation of offspring development evolved to a heightened degree, with the ability to modify development at multiple time points. Modern metabolic diseases may arise due to a mismatch between maternal regulation and eventual circumstances of the offspring, and due to a large proportion of mothers that exceed past evolutionary norms in body fat and pregnancy weight gain such that maternal signals may no longer be within the adaptive range.

The Microbiome and Its Impact on Disease in the Preterm Patient

Emerging technologies derived largely from the Human Genome Project are being applied to evaluating the intestinal microbiota in preterm infants. The microbial ecology of the developing intestine is highly related to health and disease and new discoveries are emerging that will help us understand disorders in the development of the intestinal microbial ecosystem and how to eventually manipulate them to prevent diseases such as necrotizing enterocolitis and late onset sepsis. Here, a brief overview of the developing microbiome as it pertains to several aspects of health and disease in the preterm infant is presented.

Mother-to-infant transmission of intestinal bifidobacterial strains has an impact on the early development of vaginally delivered infant's microbiota

Objectives

Bifidobacterium species are one of the major components of the infant's intestine microbiota. Colonization with bifidobacteria in early infancy is suggested to be important for health in later life. However, information remains limited regarding the source of these microbes. Here, we investigated whether specific strains of bifidobacteria in the maternal intestinal flora are transmitted to their infant's intestine.

Materials and Methods

Fecal samples were collected from healthy 17 mother and infant pairs (Vaginal delivery: 12; Cesarean section delivery: 5). Mother's feces were collected twice before delivery. Infant's feces were collected at 0 (meconium), 3, 7, 30, 90 days after birth. Bifidobacteria isolated from feces were genotyped by multilocus sequencing typing, and the transitions of bifidobacteria counts in infant's feces were analyzed by quantitative real-time PCR.

Results

Stains belonging to Bifidobacterium adolescentis, Bifidobacterium bifidum, Bifidobacterium catenulatum, Bifidobacterium longum subsp. longum, and Bifidobacterium pseudocatenulatum, were identified to be monophyletic between mother's and infant's intestine. Eleven out of 12 vaginal delivered infants carried at least one monophyletic strain. The bifidobacterial counts of the species to which the monophyletic strains belong, increased predominantly in the infant's intestine within 3 days after birth. Among infants delivered by C-section, monophyletic strains were not observed. Moreover, the bifidobacterial counts were significantly lower than the vaginal delivered infants until 7 days of age.

Conclusions

Among infants born vaginally, several Bifidobacterium strains transmit from the mother and colonize the infant's intestine shortly after birth. Our data suggest that the mother's intestine is an important source for the vaginal delivered infant's intestinal microbiota.

Utilization of major fucosylated and sialylated human milk oligosaccharides by isolated human gut microbes

Human milk oligosaccharides (HMOS) are not digested in the proximal intestine. In distal intestine, HMOS collectively modify the microbiota, but the response of individual bacteria to individual components of the HMOS is not well defined. Here, each of 25 major isolates of the human intestinal microbiota was fed individual major fucosylated and sialylated HMOS in anaerobic culture. This allowed for an assessment of the influence of specific HMOS on the growth and metabolic products of individual microbiota bacteria. Most Bifidobacteria spp. and Bacteroides spp. grew, induced α-L-fucosidase activity, and produced abundant lactate or short-chain fatty acids (SCFAs) when fed 2'-fucosyllactose (2'-FL), 3-FL, and lactodifucotetraose (LDFT). Lactobacillus delbrueckii ATCC7830, Enterococcus faecalis ATCC19433, and Streptococcus thermophilus ATCC19258 exhibited slight growth, pH reduction, and lactate production when supplemented with 2'-FL or 3-FL, but not LDFT. Supplementation with 3'-sialyllactose (3'-SL) and 6'-SL promoted moderate growth of Bifidobacterium longum JCM7007, 7009, 7010, 7011, 1272, 11347, ATCC15708, Bacteroides vulgatus ATCC8482, and B. thetaiotaomicron ATCC29148; accordingly, these bacteria exhibited greater neuraminidase activity and produced copious lactate, SCFA, or both. Lactobacillus delbrueckii ATCC7830 also consumed 6'-SL. In contrast, Clostridium spp., L. rhamnosus ATCC53103, E. faecalis ATCC29200, Staphylococcus spp., Enterobacter spp., and Escherichia coli K12 did not consume milk oligosaccharides nor produce appreciable acidic fermentation products. Specific Bifidobacteria and Bacteroides differentially digest specific individual HMOS, with the major fucosylated milk oligosaccharides most strongly stimulating key species of mutualist symbionts. This suggests strategies for treating dysbiosis of the microbiota and associated inflammatory disorders.

Effect of infant and follow-on formulas containing B lactis and galacto- and fructo-oligosaccharides on infection in healthy term infants

OBJECTIVE

The aim of the present study was to compare the effect of Bifidobacterium animalis subspecies lactis (B lactis) alone or with 90% galacto-oligosaccharide (GOS) and 10% fructo-oligosaccharide (FOS) on infections in infants.

METHODS

In a multicenter trial, healthy, term, newborn infants ages 42 days or younger whose mothers had decided not to breast-feed beyond this age received infant and follow-on formulas containing B lactis (10 colony-forming units/g) + GOS/FOS (0.4 g/100 mL, intention-to-treat, n = 261) or B lactis alone (10⁷ colony-forming units/g, intention-to-treat, n = 267). Investigators accessed computer-generated randomization sequences via a remote server. Infants were exclusively fed formulas until 4 to 6 months of age and along with complementary feeding thereafter up to 12 months. The primary outcome was the mean number of annual infections reported by the investigators. Secondary outcomes were mean gains in anthropometric measurements, frequency of antibiotic use, and occurrence of adverse events based on investigators' records at each visit and gastrointestinal tolerance (daily stool frequency and consistency) and volume of formula intake recorded in 6-day diaries by parents.

RESULTS

Mean ± standard deviation infection rates in infants followed up to 12 months (full analysis set) were 4.9 ± 3.2 per infant per year in the B lactis + GOS/FOS group (n = 219) and 4.5 ± 3.0 per infant per year in the B lactis group (n = 220; analysis of variance, P = 0.18). Mean daily weight gain was slightly lower in the B lactis + GOS/FOS than the B lactis group (16.1 ± 2.9 vs 16.6 ± 2.6 g/day, P = 0.046), but was not clinically significant. Other outcomes were not significantly different between groups.

CONCLUSIONS

Formulas containing B lactis + GOS/FOS did not reduce infection rates beyond those containing only B lactis.

Variation in consumption of human milk oligosaccharides by infant gut-associated strains of Bifidobacterium breve

Human milk contains a high concentration of complex oligosaccharides that influence the composition of the intestinal microbiota in breast-fed infants. Previous studies have indicated that select species such as Bifidobacterium longum subsp. infantis and Bifidobacterium bifidum can utilize human milk oligosaccharides (HMO) in vitro as the sole carbon source, while the relatively few B. longum subsp. longum and Bifidobacterium breve isolates tested appear less adapted to these substrates. Considering the high frequency at which B. breve is isolated from breast-fed infant feces, we postulated that some B. breve strains can more vigorously consume HMO and thus are enriched in the breast-fed infant gastrointestinal tract. To examine this, a number of B. breve isolates from breast-fed infant feces were characterized for the presence of different glycosyl hydrolases that participate in HMO utilization, as well as by their ability to grow on HMO or specific HMO species such as lacto-N-tetraose (LNT) and fucosyllactose. All B. breve strains showed high levels of growth on LNT and lacto-N-neotetraose (LNnT), and, in general, growth on total HMO was moderate for most of the strains, with several strain differences. Growth and consumption of fucosylated HMO were strain dependent, mostly in isolates possessing a glycosyl hydrolase family 29 α-fucosidase. Glycoprofiling of the spent supernatant after HMO fermentation by select strains revealed that all B. breve strains can utilize sialylated HMO to a certain extent, especially sialyl-lacto-N-tetraose. Interestingly, this specific oligosaccharide was depleted before neutral LNT by strain SC95. In aggregate, this work indicates that the HMO consumption phenotype in B. breve is variable; however, some strains display specific adaptations to these substrates, enabling more vigorous consumption of fucosylated and sialylated HMO. These results provide a rationale for the predominance of this species in breast-fed infant feces and contribute to a more accurate picture of the ecology of the developing infant intestinal microbiota.

Exposure of Bifidobacterium longum subsp. infantis to Milk Oligosaccharides Increases Adhesion to Epithelial Cells and Induces a Substantial Transcriptional Response

In this study, we tested the hypothesis that milk oligosaccharides may contribute not only to selective growth of bifidobacteria, but also to their specific adhesive ability. Human milk oligosaccharides (3'sialyllactose and 6'sialyllactose) and a commercial prebiotic (Beneo Orafti P95; oligofructose) were assayed for their ability to promote adhesion of Bifidobacterium longum subsp. infantis ATCC 15697 to HT-29 and Caco-2 human intestinal cells. Treatment with the commercial prebiotic or 3'sialyllactose did not enhance adhesion. However, treatment with 6'sialyllactose resulted in increased adhesion (4.7 fold), while treatment with a mixture of 3'- and 6'-sialyllactose substantially increased adhesion (9.8 fold) to HT-29 intestinal cells. Microarray analyses were subsequently employed to investigate the transcriptional response of B. longum subsp. infantis to the different oligosaccharide treatments. This data correlated strongly with the observed changes in adhesion to HT-29 cells. The combination of 3'- and 6'-sialyllactose resulted in the greatest response at the genetic level (both in diversity and magnitude) followed by 6'sialyllactose, and 3'sialyllactose alone. The microarray data was further validated by means of real-time PCR. The current findings suggest that the increased adherence phenotype of Bifidobacterium longum subsp. infantis resulting from exposure to milk oligosaccharides is multi-faceted, involving transcription factors, chaperone proteins, adhesion-related proteins, and a glycoside hydrolase. This study gives additional insight into the role of milk oligosaccharides within the human intestine and the molecular mechanisms underpinning host-microbe interactions.

Mode of delivery and early nutrition modulate microbial colonization and fermentation products in neonatal piglets

Colonization of the intestinal microbiota after birth plays an important role in development of the neonatal gastrointestinal and immune systems. Two key environmental factors that influence the colonization pattern are delivery mode and nutrition. In this study, the impact of delivery mode and nutrition on microbial colonization and metabolic activity was investigated in the pig model. Vaginally (VD) or caesarean- (CD) delivered piglets were sow-reared (SR) or fed formula alone (FF) or with 4 g/L prebiotics [1:1 ratio of short-chain fructo-oligosaccharides (scFOS) and polydextrose (PDX); FP]. Intestinal contents were collected on d 7 and 14. SR piglets harbored different microbial populations from FF and FP piglets in ileum and ascending colon (AC). On d 7, FF piglets had a greater abundance of Clostridium XIVa in AC, but lower total bacteria, Clostridium XIVa, and Lactobacillus spp. in ileum and Fecalibacterium prausnitzii in AC compared with FP piglets. On d 14, total bacteria were more abundant in FP than FF piglets. Butyrate, isobutyrate, valerate, and isovalerate concentrations in AC were greater in SR piglets compared with FF or FP piglets. At both sampling days, acetate concentrations in AC were similar between the SR and FF groups, whereas propionate was higher in the SR compared with FF group. Delivery mode also significantly affected microbial populations. Bacterial densities differed in AC for Bacteroides-Prevotella at d 7 and Clostridium XIVa at d 14, being higher in VD piglets. Correspondingly, VD piglets had higher propionate in ileum and propionate and butyrate in AC compared with CD piglets. Our results indicate that both delivery mode and nutrition affect microbial composition and metabolic activity. Supplementation of scFOS/PDX to formula modulates microbial colonization and produces a SCFA pattern closer to that of SR piglets.

Genomic and phenotypic evidence for probiotic influences of Lactobacillus gasseri on human health

Certain lactic acid bacteria (LAB) have the capacity to occupy mucosal niches of humans, including the oral cavity, gastrointestinal tract, and vagina. Among commensal, LAB are species of the acidophilus complex, which have proven to be a substantial reservoir for microorganisms with probiotic attributes. Specifically, Lactobacillus gasseri is an autochthonous microorganism which has been evaluated for probiotic activity based on the availability of genome sequence and species-specific adaptation to the human mucosa. Niche-related characteristics of L. gasseri contributing to indigenous colonization include tolerance of low pH environments, resistance to bile salts, and adhesion to the host epithelium. In humans, L. gasseri elicits various health benefits through its antimicrobial activity, bacteriocin production, and immunomodulation of the innate and adaptive systems. The genomic and empirical evidence supporting use of L. gasseri in probiotic applications is substantiated by clinical trial data displaying maintenance of vaginal homeostasis, mitigation of Helicobacter pylori infection, and amelioration of diarrhea.

Consumption of human milk glycoconjugates by infant-associated bifidobacteria: mechanisms and implications

Human milk is a rich source of nutrients and energy, shaped by mammalian evolution to provide all the nutritive requirements of the newborn. In addition, several molecules in breast milk act as bioactive agents, playing an important role in infant protection and guiding a proper development. While major breast milk nutrients such as lactose, lipids and proteins are readily digested and consumed by the infant, other molecules, such as human milk oligosaccharides and glycosylated proteins and lipids, can escape intestinal digestion and transit through the gastrointestinal tract. In this environment, these molecules guide the composition of the developing infant intestinal microbiota by preventing the colonization of enteric pathogens and providing carbon and nitrogen sources for other colonic commensals. Only a few bacteria, in particular Bifidobacterium species, can gain access to the energetic content of milk as it is displayed in the colon, probably contributing to their predominance in the intestinal microbiota in the first year of life. Bifidobacteria deploy exquisite molecular mechanisms to utilize human milk oligosaccharides, and recent evidence indicates that their activities also target other human milk glycoconjugates. Here, we review advances in our understanding of how these microbes have been shaped by breast milk components and the strategies associated with their consumption of milk glycoconjugates.

The altered gut microbiome and necrotizing enterocolitis

Current evidence highlights the importance of developing a healthy intestinal microbiota in the neonate. Many aspects that promote health or disease are related to the homeostasis of these intestinal microbiota. Their delicate equilibrium could be strongly influenced by the intervention that physicians perform as part of the medical care of the neonate, especially preterm infants. As awareness of the importance of the development and maintenance of these intestinal flora increase and newer molecular techniques are developed, it will be possible to provide better care of infants with interventions that will have long-lasting effects.

Proteomic analysis of Bifidobacterium longum subsp. infantis reveals the metabolic insight on consumption of prebiotics and host glycans

Bifidobacterium longum subsp. infantis is a common member of the intestinal microbiota in breast-fed infants and capable of metabolizing human milk oligosaccharides (HMO). To investigate the bacterial response to different prebiotics, we analyzed both cell wall associated and whole cell proteins in B. infantis. Proteins were identified by LC-MS/MS followed by comparative proteomics to deduce the protein localization within the cell. Enzymes involved in the metabolism of lactose, glucose, galactooligosaccharides, fructooligosaccharides and HMO were constitutively expressed exhibiting less than two-fold change regardless of the sugar used. In contrast, enzymes in N-Acetylglucosamine and sucrose catabolism were induced by HMO and fructans, respectively. Galactose-metabolizing enzymes phosphoglucomutase, UDP-glucose 4-epimerase and UTP glucose-1-P uridylytransferase were expressed constitutively, while galactokinase and galactose-1-phosphate uridylyltransferase, increased their expression three fold when HMO and lactose were used as substrates for cell growth. Cell wall-associated proteomics also revealed ATP-dependent sugar transport systems associated with consumption of different prebiotics. In addition, the expression of 16 glycosyl hydrolases revealed the complete metabolic route for each substrate. Mucin, which possesses O-glycans that are structurally similar to HMO did not induced the expression of transport proteins, hydrolysis or sugar metabolic pathway indicating B. infantis do not utilize these glycoconjugates.

Utilization of galactooligosaccharides by Bifidobacterium longum subsp. infantis isolates

Prebiotics are non-digestible substrates that stimulate the growth of beneficial microbial populations in the intestine, especially Bifidobacterium species. Among them, fructo- and galacto-oligosaccharides are commonly used in the food industry, especially as a supplement for infant formulas. Mechanistic details on the enrichment of bifidobacteria by these prebiotics are important to understand the effects of these dietary interventions. In this study the consumption of galactooligosaccharides was studied for 22 isolates of Bifidobacterium longum subsp. infantis, one of the most representative species in the infant gut microbiota. In general all isolates showed a vigorous growth on these oligosaccharides, but consumption of larger galactooligosaccharides was variable. Bifidobacterium infantis ATCC 15697 has five genes encoding β-galactosidases, and three of them were induced during bacterial growth on commercial galactooligosaccharides. Recombinant β-galactosidases from B. infantis ATCC 15697 displayed different preferences for β-galactosides such as 4' and 6'-galactobiose, and four β-galactosidases in this strain released monosaccharides from galactooligosaccharides. Finally, we determined the amounts of short chain fatty acids produced by strain ATCC 15697 after growth on different prebiotics. We observed that biomass and product yields of substrate were higher for lactose and galactooligosaccharides, but the amount of acids produced per cell was larger after growth on human milk oligosaccharides. These results provide a molecular basis for galactooligosaccharide consumption in B. infantis, and also represent evidence for physiological differences in the metabolism of prebiotics that might have a differential impact on the host.

The principal fucosylated oligosaccharides of human milk exhibit prebiotic properties on cultured infant microbiota

Breast-fed infant microbiota is typically rich in bifidobacteria. Herein, major human milk oligosaccharides (HMOS) are assessed for their ability to promote the growth of bifidobacteria and to acidify their environment, key features of prebiotics. During in vitro anaerobic fermentation of infant microbiota, supplementation by HMOS significantly decreased the pH even greater than supplementation by fructooligosaccharide (FOS), a prebiotic positive control. HMOS elevated lactate concentrations, increased the proportion of Bifidobacterium spp. in culture, and through their fermentation into organic acids, decreased the proportion of Escherichia and Clostridium perfringens. Three principal components of HMOS, 2'-fucosyllactose, lactodifucotetraose and 3-fucosyllactose, were consumed in these cultures. These three principal oligosaccharides of human milk were then individually tested as supplements for in vitro growth of four individual representative strains of infant gut microbes. Bifidobacterium longum JCM7007 and B. longum ATCC15697 efficiently consumed oligosaccharides and produced abundant lactate and short-chain fatty acids, resulting in significant pH reduction. The specificity of fermentation differed by microbe species and strain and by oligosaccharide structure. Escherichia coli K12 and C. perfringens did not utilize appreciable fucosylated oligosaccharides, and a typical mixture of organic acid fermentation products inhibited their growth. In summary, 2'-fucosyllactose, lactodifucotetraose, and 3-fucosyllactose, when cultured with B. longum JCM7007 and B. longum ATCC15697, exhibit key characteristics of a prebiotic in vitro. If these bifidobacteria are representative of pioneering or keystone species for human microbiota, fucosylated HMOS could strongly promote colonization and maintenance of a mutualist symbiotic microbiome. Thus, these simple glycans could mediate beneficial effects of human milk on infant health.

Metabolism of oligosaccharides and starch in lactobacilli: a review

Oligosaccharides, compounds that are composed of 2-10 monosaccharide residues, are major carbohydrate sources in habitats populated by lactobacilli. Moreover, oligosaccharide metabolism is essential for ecological fitness of lactobacilli. Disaccharide metabolism by lactobacilli is well understood; however, few data on the metabolism of higher oligosaccharides are available. Research on the ecology of intestinal microbiota as well as the commercial application of prebiotics has shifted the interest from (digestible) disaccharides to (indigestible) higher oligosaccharides. This review provides an overview on oligosaccharide metabolism in lactobacilli. Emphasis is placed on maltodextrins, isomalto-oligosaccharides, fructo-oligosaccharides, galacto-oligosaccharides, and raffinose-family oligosaccharides. Starch is also considered. Metabolism is discussed on the basis of metabolic studies related to oligosaccharide metabolism, information on the cellular location and substrate specificity of carbohydrate transport systems, glycosyl hydrolases and phosphorylases, and the presence of metabolic genes in genomes of 38 strains of lactobacilli. Metabolic pathways for disaccharide metabolism often also enable the metabolism of tri- and tetrasaccharides. However, with the exception of amylase and levansucrase, metabolic enzymes for oligosaccharide conversion are intracellular and oligosaccharide metabolism is limited by transport. This general restriction to intracellular glycosyl hydrolases differentiates lactobacilli from other bacteria that adapted to intestinal habitats, particularly Bifidobacterium spp.

The human milk microbiota: origin and potential roles in health and disease

Human milk has been traditionally considered sterile; however, recent studies have shown that it represents a continuous supply of commensal, mutualistic and/or potentially probiotic bacteria to the infant gut. Culture-dependent and -independent techniques have revealed the dominance of staphylococci, streptococci, lactic acid bacteria and bifidobacteria in this biological fluid, and their role on the colonization of the infant gut. These bacteria could protect the infant against infections and contribute to the maturation of the immune system, among other functions. Different studies suggest that some bacteria present in the maternal gut could reach the mammary gland during late pregnancy and lactation through a mechanism involving gut monocytes. Thus, modulation of maternal gut microbiota during pregnancy and lactation could have a direct effect on infant health. On the other hand, mammary dysbiosis may lead to mastitis, a condition that represents the first medical cause for undesired weaning. Selected strains isolated from breast milk can be good candidates for use as probiotics. In this review, their potential uses for the treatment of mastitis and to inhibit mother-to-infant transfer of HIV are discussed.

Bifidobacteria isolated from infants and cultured on human milk oligosaccharides affect intestinal epithelial function

OBJECTIVES

Human milk oligosaccharides (HMOs) are the third most abundant component of breast milk. Our laboratory has previously revealed gene clusters specifically linked to HMO metabolism in selected bifidobacteria isolated from fecal samples of infants. Our objective was to test the hypothesis that growth of selected bifidobacteria on HMO stimulates the intestinal epithelium.

METHODS

Caco-2 and HT-29 cells were incubated with lactose (LAC)- or HMO-grown Bifidobacterium longum subsp infantis (B infantis) or B bifidum. Bacterial adhesion and translocation were measured by real-time quantitative polymerase chain reaction. Expression of pro- and anti-inflammatory cytokines and tight junction proteins was analyzed by real-time reverse transcriptase. Distribution of tight junction proteins was measured using immunofluorescent microscopy.

RESULTS

We showed that HMO-grown B infantis had a significantly higher rate of adhesion to HT-29 cells compared with B bifidum. B infantis also induced expression of a cell membrane glycoprotein, P-selectin glycoprotein ligand-1. Both B infantis and B bifidum grown on HMO caused less occludin relocalization and higher expression of anti-inflammatory cytokine, interleukin-10 compared with LAC-grown bacteria in Caco-2 cells. B bifidum grown on HMO showed higher expression of junctional adhesion molecule and occludin in Caco-2 cells and HT-29 cells. There were no significant differences between LAC or HMO treatments in bacterial translocation.

CONCLUSIONS

The study provides evidence for the specific relation between HMO-grown bifidobacteria and intestinal epithelial cells. To our knowledge, this is the first study describing HMO-induced changes in the bifidobacteria-intestinal cells interaction.

Identification and accurate quantitation of biological oligosaccharide mixtures

Structure-specific characterization and quantitation is often required for effective functional studies of oligosaccharides. Inside the gut, HMOs are preferentially bound and catabolized by the beneficial bacteria. HMO utility by these bacteria employs structure-specific catabolism based on a number of glycosidases. Determining the activity of these enzymes requires accurate quantitation of a large number of structures. In this study, we describe a method for the quantitation of human milk oligosaccharide (HMO) structures employing LC/MS and isotopically labeled internal standards. Data analysis was accomplished with a newly developed software tool, LC/MS Searcher, that employs a reference structure library to process LC/MS data yielding structural identification with accurate quantitation. The method was used to obtain a meta-enzyme analysis of bacteria, the simultaneous characterization of all glycosidases employed by bacteria for the catabolism of milk oligosaccharides. Analysis of consumed HMO structures confirmed the utility of a β-1,3-galactosidase in Bifidobacterium longum subsp. infantis ATCC 15697 (B. infantis). In comparison, Bifidobacterium breve ATCC 15700 showed significantly less HMO catabolic activity compared to B. infantis.

Lacto-N-tetraose, fucosylation, and secretor status are highly variable in human milk oligosaccharides from women delivering preterm

Breast milk is the ideal nutrition for term infants but must be supplemented to provide adequate growth for most premature infants. Human milk oligosaccharides (HMOs) are remarkably abundant and diverse in breast milk and yet provide no nutritive value to the infant. HMOs appear to have at least two major functions: prebiotic activity (stimulation of the growth of commensal bacteria in the gut) and protection against pathogens. Investigations of HMOs in milk from women delivering preterm have been limited. We present the first detailed mass spectrometric analysis of the fucosylation and sialylation in HMOs in serial specimens of milk from 15 women delivering preterm and 7 women delivering at term using nanohigh performance liquid chromatography chip/time-of-flight mass spectrometry. A mixed-effects model with Levene's test was used for the statistical analyses. We find that lacto-N-tetraose, a core HMO, is both more abundant and more highly variable in the milk of women delivering preterm. Furthermore, fucosylation in preterm milk is not as well regulated as in term milk, resulting in higher within and between mother variation in women delivering preterm vs term. Of particular clinical interest, the α1,2-linked fucosylated oligosaccharide 2'-fucosyllactose, an indicator of secretor status, is not consistently present across lactation of several mothers that delivered preterm. The immaturity of HMO production does not appear to resolve over the time of lactation and may have relevance to the susceptibility of premature infants to necrotizing enterocolitis, late onset sepsis, and related neurodevelopmental impairments.

Release and utilization of N-acetyl-D-glucosamine from human milk oligosaccharides by Bifidobacterium longum subsp. infantis

Human milk contains high amounts of complex oligosaccharides, which can be utilized especially by Bifidobacterium species in the infant gut as a carbon and energy source. N-acetyl-D-glucosamine is a building block of these oligosaccharides, and molecular details on the release and utilization of this monosaccharide are not fully understood. In this work we have studied some of the enzymatic properties of three N-acetyl-β-D-hexosaminidases encoded by the genome of the intestinal isolate Bifidobacterium longum subsp. infantis ATCC 15697 and the gene expression of the corresponding genes during bacterial growth on human milk oligosaccharides. These enzymes belong to the glycosyl hydrolase family 20, with several homologs in bifidobacteria. Their optimum pH was 5.0 and optimum temperature was 37 °C. The three enzymes were active on the GlcNAcβ1-3 linkage found in lacto-N-tetraose, the most abundant human milk oligosaccharide. Blon_0459 and Blon_0732, but not Blon_2355, cleaved branched GlcNAcβ1-6 linkages found in lacto-N-hexaose, another oligosaccharide abundant in breast milk. Bifidobacterium infantis N-acetyl-β-D-hexosaminidases were induced during early growth in vitro on human milk oligosaccharides, and also during growth on lacto-N-tetraose or lacto-N-neotetraose. The up-regulation of enzymes that convert this monosaccharide into UDP-N-acetylglucosamine by human milk oligosaccharides suggested that this activated sugar is used in peptidoglycan biosynthesis. These results emphasize the complexity of human milk oligosaccharide consumption by this infant intestinal isolate, and provide new clues into this process.

The human microbiome and its potential importance to pediatrics

The human body is home to more than 1 trillion microbes, with the gastrointestinal tract alone harboring a diverse array of commensal microbes that are believed to contribute to host nutrition, developmental regulation of intestinal angiogenesis, protection from pathogens, and development of the immune response. Recent advances in genome sequencing technologies and metagenomic analysis are providing a broader understanding of these resident microbes and highlighting differences between healthy and disease states. The aim of this review is to provide a detailed summary of current pediatric microbiome studies in the literature, in addition to highlighting recent findings and advancements in studies of the adult microbiome. This review also seeks to elucidate the development of, and factors that could lead to changes in, the composition and function of the human microbiome.

Development of tools to study lacto-N-biosidase: an important enzyme involved in the breakdown of human milk oligosaccharides

Milk and sugar? The elucidation of the catalytic mechanism and the development of the first known inhibitor for lacto-N-biosidases, which are important enzymes involved in the breakdown of human milk oligosaccharides, are described.

Microbial composition and in vitro fermentation patterns of human milk oligosaccharides and prebiotics differ between formula-fed and sow-reared piglets

The microbial composition and in vitro fermentation characteristics of human milk oligosaccharides (HMO), lacto-N-neotetraose (LNnT), a 2:1 mixture of polydextrose (PDX) and galactooligosaccharides (GOS), and short-chain fructooligosaccharides (scFOS) by pooled ascending colonic microbiota from 9- and 17-d-old formula-fed (FF) and sow-reared (SR) piglets were assessed. pH change and gas, SCFA, and lactate production were determined after 0, 2, 4, 8, and 12 h of incubation. In most donor groups, the pH change was greater for scFOS fermentation and lower for PDX/GOS than for other substrates. LNnT fermentation produced larger amounts of gas, total SCFA, acetate, and butyrate than did the other substrates, whereas HMO and scFOS produced higher amounts of propionate and lactate, respectively. In general, pH change, total SCFA, acetate, and propionate production were greater in pooled inoculum from FF and 9-d-old piglets, whereas SR-derived inoculum produced higher amounts of butyrate and lactate after 4 h fermentation. Gut microbiota were assessed by 16S ribosomal RNA V3 gene denaturing gradient gel electrophoresis analysis and real-time qPCR. Microbial structures differed among the 4 groups before fermentation, with higher counts of Bifidobacterium in SR piglets and higher counts of Clostridium cluster IV, XIVa, and Bacteroides vulgatus in FF piglets. Lactobacillus counts were higher in 9-d-old piglets than in 17-d-old piglets, regardless of diet. Bifidobacterium, Bacteroides, and clostridial species increased after 8 and 12 h fermentation on most substrates. In summary, piglet diet and age affect gut microbiota, leading to different fermentation patterns. HMO have potential prebiotic effects due to their effects on SCFA production and microbial modulation.

Bifidobacterium longum subsp. infantis ATCC 15697 α-fucosidases are active on fucosylated human milk oligosaccharides

Bifidobacterium longum subsp. infantis ATCC 15697 utilizes several small-mass neutral human milk oligosaccharides (HMOs), several of which are fucosylated. Whereas previous studies focused on endpoint consumption, a temporal glycan consumption profile revealed a time-dependent effect. Specifically, among preferred HMOs, tetraose was favored early in fermentation, with other oligosaccharides consumed slightly later. In order to utilize fucosylated oligosaccharides, ATCC 15697 possesses several fucosidases, implicating GH29 and GH95 α-L-fucosidases in a gene cluster dedicated to HMO metabolism. Evaluation of the biochemical kinetics demonstrated that ATCC 15697 expresses three fucosidases with a high turnover rate. Moreover, several ATCC 15697 fucosidases are active on the linkages inherent to the HMO molecule. Finally, the HMO cluster GH29 α-L-fucosidase possesses a crystal structure that is similar to previously characterized fucosidases.

Preterm milk oligosaccharides during the first month of lactation

OBJECTIVE

Oligosaccharides represent one of the main components of human milk, and they have been assigned important biological functions for newborns. Qualitatively and quantitatively, their presence in milk is strictly related to the expression of the mother's Se and/or Le genes, on the basis of which 4 different milk groups have been described. The aim of the study was to provide new data on the oligosaccharide composition of preterm milk in relation to the 4 groups.

METHODS

High-pH anion-exchange chromatography was used to quantify levels of 23 oligosaccharides and lactose in 252 milk samples collected from 63 mothers during the first month of lactation and to identify the 4 milk groups.

RESULTS

Substantial differences in oligosaccharide contents were found within the groups and were strictly related to the presence or absence of specific fucosyl-oligosaccharides. The highest concentration was found in group 1 (>20 g/L), the lowest level was found in group 4 (∼10 g/L), and intermediate values were observed in groups 2 and 3. No statistically significant differences in lactose concentrations were observed among the groups.

CONCLUSIONS

Our data confirm lower lactose concentrations in preterm milk, compared with term milk, and they provide the first detailed characterization of oligosaccharides in preterm milk, demonstrating important differences in oligosaccharide contents in the 4 groups. These differences might exert an influence on several biological functions that are particularly important for preterm infants and currently are attributed to milk oligosaccharides.