Systematic review of the concentrations of oligosaccharides in human milk

Quantitative nuclear magnetic analysis of human milk oligosaccharides 2'-fucosyllactose and 3-fucosyllactose in complicated food matrices

Human milk oligosaccharides (HMOs) are the third most abundant solid component in breast milk, which is essential for the healthy growth of infants. 2'-fucosyllactose (2'-FL) and 3-fucosyllactose (3-FL) are the main components of HMOs. In this study, we developed and validated a quantitative nuclear magnetic resonance (qNMR) method for determining HMOs in different complex food matrices. The spectra of HMOs often overlap with impurities in the samples, which hampers quantification using the conventional integral method. We overcame this obstacle by building the Global Spectrum Deconvolution-area coefficients algorithm. The method proved to be precise, yielding satisfactory results in terms of precision (RSD% 0.5-1.9), trueness (bias% 1.9-8.2), and recovery (90.5-106.6 %). The limit of quantification for 2'-FL was 0.10 mg/mL, and for 3-FL, it was 0.15 mg/mL. A comparison using Deming regression between the existing high-performance liquid chromatography method and the developed qNMR method for determining HMOs demonstrated the high accuracy of the qNMR method. The proposed method allows for high-throughput measurements of large-volume samples due to its simple and fast sample preparation. Therefore, the method is an essential tool for determining HMOs in various complex foods.

Human Milk Feeding in Inherited Metabolic Disorders: A Systematic Review of Growth, Metabolic Control, and Neurodevelopment Outcomes

Human milk (HM) is the optimal source of nutrition for infants. Yet the suitability of HM macronutrient composition, paired with the challenge of regulating HM intake, may deserve some consideration for infants with inherited metabolic disorders (IMDs) requiring restrictive and controlled dietary management. Except for classic galactosemia, HM feeding is expected to be feasible, allowing infants to maintain metabolic stability, while growing and developing optimally. However, information about HM feeding in nonphenylketonuria (PKU) literature is scarce. In this systematic review, 52 studies were included, representing 861 infants (86% PKU) receiving HM after IMD diagnosis (mean duration 4-10 months depending on the IMD). For non-PKU IMDs (e.g., other amino acidopathies, urea cycle disorders, organic acidemias, fatty acid oxidation disorders), outcomes of HM feeding were available for few infants, except for medium-chain acyl-CoA dehydrogenase (MCAD) deficiency (n = 48). In PKU, HM feeding combined with phenylalanine-free formula, led to adequate metabolic control (25 studies), growth (15 studies), and neurodevelopment (10 studies). For other IMDs, more evidence is required, but the limited data suggest that HM feeding is possible, with attentive monitoring and disease-specific formula supplementation where applicable. In MCAD deficiency, ensuring adequate HM intake is essential, as symptoms were more frequently reported in exclusively breastfed infants. No IMD-specific articles were found on the relationship between HM feeding and many other outcomes of interest (e.g., immune status or comorbidity risk later in life). With the exception of galactosemia, HM feeding is expected to benefit infants with IMD. More data should be published for IMDs other than PKU.

Recent advances in the science of human milk oligosaccharides

Human colostrum and mature milk contain oligosaccharides (Os), designated as human milk oligosaccharides (HMOs). Approximately 200 varieties of HMOs have been characterized. Although HMOs are not utilized as an energy source by infants, they have important protective functions, including pathogenic bacteria and viral infection inhibitors and immune modulators, among other functions, and HMOs stimulate brain-nerve development. The Os concentration is average 11 g/L in human milk but >100 mg/L in mature bovine milk, which is used to manufacture infant formula, suggesting that human-identical milk oligosaccharides (HiMOs) should be incorporated into milk substitutes. Some infant formulas incorporating 2'-fucosyllactose and lacto-N-neotetraose are now commercially available, and intervention trials have been concluded. We review basic HMO information, including their chemical structures and concentrations, attempts to synthesize HMOs at small and plant scale, studies that clarified HMO biological functions, and interventions with milk substitutes incorporating HiMOs in formula-fed infants.

Lifelong partners: Gut microbiota-immune cell interactions from infancy to old age

Our immune system and gut microbiota are intricately coupled from birth, both going through maturation during early life and senescence during aging almost in a synchronized fashion. The symbiotic relationship between the human host and microbiota is critically dependent on a healthy immune system to keep our microbiota in check, while the microbiota provides essential functions to promote the development and fitness of our immune system. The partnership between our immune system and microbiota is particularly important during early life, when microbial ligands and metabolites shape the development of the immune cells and immune tolerance; during aging, having sufficient beneficial gut bacteria is critical for the maintenance of intact mucosal barriers, immune metabolic fitness, and strong immunity against pathogens. The immune system during childhood is programmed, with the support of the microbiota, to develop robust immune tolerance, and limit autoimmunity and metabolic dysregulation, which are prevalent during aging. This review comprehensively explores the mechanistic underpinnings of gut microbiota-immune cell interactions during infancy and old age, with the goal to gain a better understanding of potential strategies to leverage the gut microbiota to combat age-related immune decline.

Dietary nucleotides drive changes in infant fecal microbiota in vitro and gut microbiota-gut-brain development in neonatal rats: A potential "nitrogen source" for early microbiota growth

Various dietary factors in human milk are important nutrients for the formation of the infant gut microbiota (GM). While promoting the growth of the GM, some human milk components that are difficult to absorb and utilize will be broken down by the GM, and converted into nutrients that the baby can use, such as breast milk oligosaccharides-the 'carbon source' for infant GM. This study reveals that nucleotides (NTs), significant non-protein nitrogen sources in human milk, can enhance the abundance of beneficial microbial genera such as g_Bifidobacterium, g_Bacteroides, and g_Blautia in in vitro fecal fermentation fluids of infants at low doses (2 mg/mL). Conversely, high doses of NTs (20 mg/mL) increased the abundance of g_Escherichia-Shigella. Furthermore, low-dose NTs fermentation broth significantly enhanced the expression of neurodevelopmental marker genes such as Tuj1, Sox2, Dcx, and NeuN in NE-4C neural stem cells, whereas a single NTs digestion broth did not exhibit significant activity. However, in vivo studies using neonatal rats as a model demonstrated that both low-dose NTs fermentation broth and NTs digestive juices promoted behavioral development in neonatal rats (PND 20) and neuron maturation in the prefrontal cortex and hippocampus. Non-targeted metabolomics results indicate that low-dose dietary NTs promote the production of certain neuroregulatory metabolites in infant fecal fermentation, such as uridine, L-tyrosine, L-glutamic acid, and succinic acid. These findings suggest that NTs may serve as an important "nitrogen source" during GM formation in early life and have a dose effect in driving the development of the microbiota-gut-brain axis in early life.

Comparative study of the oligosaccharide profile in goat, bovine, sheep, and human milk whey

Milk oligosaccharides are high added value compounds that could be obtained by exploiting cheese whey, a byproduct of dairy industry. The objective was to compare the abundance and diversity of oligosaccharides in whey samples from domestic animals and humans. During fresh cheese making, whey samples were collected and analyzed by untargeted and targeted small molecule analysis using high-resolution mass-spectrometry. A great similarity in the metabolite profile between goat and sheep was observed. Up to 11 oligosaccharides were observed in the sheep whey from those typically found in humans. The concentration of 2'-Fucosyllactose (0.136 ± 0.055 g/L) and 3-Fucosyllactose (0.079 ± 0.009 g/L) were significantly higher (p-value <0.01) in sheep whey, while the concentration of 3'-Sialyllactose (0.826 ± 0.638 g/L) was higher in goat whey. No significant differences were observed between goat and sheep whey for the other oligosaccharides (p-value >0.05). Therefore, sheep and goat whey could become an important source of oligosaccharides through their revalorization.

Human milk oligosaccharides: bridging the gap in intestinal microbiota between mothers and infants

Breast milk is an essential source of infant nutrition. It is also a vital determinant of the structure and function of the infant intestinal microbial community, and it connects the mother and infant intestinal microbiota. Human milk oligosaccharides (HMOs) are a critical component in breast milk. HMOs can reach the baby's colon entirely from milk and become a fermentable substrate for some intestinal microorganisms. HMOs can enhance intestinal mucosal barrier function and affect the intestinal function of the host through immune function, which has a therapeutic effect on specific infant intestinal diseases, such as necrotizing enterocolitis. In addition, changes in infant intestinal microbiota can reflect the maternal intestinal microbiota. HMOs are a link between the maternal intestinal microbiota and infant intestinal microbiota. HMOs affect the intestinal microbiota of infants and are related to the maternal milk microbiota. Through breastfeeding, maternal microbiota and HMOs jointly affect infant intestinal bacteria. Therefore, HMOs positively influence the establishment and balance of the infant microbial community, which is vital to ensure infant intestinal function. Therefore, HMOs can be used as a supplement and alternative therapy for infant intestinal diseases.

From mother's milk to structural insights: 1H-15N NMR analysis of Lewis X antigen-bearing oligosaccharides isolated from human milk

Human milk oligosaccharides (HMOs) are complex unconjugated glycans abundant in breast milk, with vital roles in infant nutrition and health. The structural elucidation of HMOs remains challenging due to their diverse compositions and isomeric complexities. This study presents a novel approach employing 1H-15N NMR correlations to pinpoint and characterize HMOs, LNH, LNnH, and their fucosylated derivatives including those of bearing the Lewis X motif. Isolated from human milk, these hexa-, hepta-, and octasaccharides were extensively analysed by NMR. This enabled their first complete 1H, 13C and 15N resonance assignments. Using 1H-15N HSQC experiments, the distinctive 1H-15N correlations of GlcNAc units within the HMOs provided structural fingerprints, allowing for unequivocal differentiation of isomeric structures and fucosylation patterns. Results demonstrate the potential of 1H-15N NMR spectroscopy in decoding complex HMO structures, offering new perspectives on their detailed structural characterization and contributing to a deeper understanding of their potential benefits.

Highly efficient production of lacto-N-tetraose in plasmid-free Escherichia coli through chromosomal integration of multicopy key glycosyltransferase genes

Lacto-N-tetraose (LNT) is a functional human milk oligosaccharide (HMO) commercially added to infant formula. Metabolically engineered strains for efficient production of LNT have been widely constructed. However, most of them rely on the use of plasmids, which might bring metabolic burden and the antibiotic issue. In this study, we attempted to construct a plasmid-free Escherichia coli MG1655 for LNT biosynthesis. Firstly, lacZ gene was disrupted and lacY expression was enhanced to improve the bioavailability of lactose as the initial substrate. Three copies of lgtA (encoding for β1,3-N-acetylglucosaminyltransferase) were integrated into the chromosome, enabling the highly efficient production of lacto-N-triose II (LNTri II) as the direct precursor of LNT. Efficient production of LNT was then optimized by multicopy integration of wbgO (encoding for β1,3-galactosyltransferase), disruption of the competitive pathways, and strengthening of UDP-galactose supply and oligosaccharide efflux. The final titer reached 6.99 and 42.38 g/L in shake-flask and fed-batch cultivation, respectively.

Human milk microbiota and oligosaccharides in colostrum and mature milk: comparison and correlation

Background

The interaction between the human breast milk microbiota and human milk oligosaccharides (HMOs) plays a crucial role in the healthy growth and development of infants. We aimed to clarify the link between the breast milk microbiota and HMOs at two stages of lactation.

Methods

The microbiota and HMOs of 20 colostrum samples (C group, 1-5 days postpartum) and 20 mature milk samples (S group, 42 days postpartum) collected from postpartum mothers were analyzed using 16S rRNA gene high-throughput sequencing and high-performance liquid chromatography-tandem mass spectrometry.

Result

The total average HMO content was significantly higher in the C group than in the S group (6.76 ± 1.40 g/L vs. 10.27 ± 2.00 g/L, p < 0.05). Among the HMOs, the average values of 2'-fucosyllactose (2'-FL, 1.64 ± 1.54 g/L vs. 3.03 ± 1.79 g/L), 3'-sialyllactose (3'-SL, 0.10 ± 0.02 g/L vs. 0.21 ± 0.06), 6'-SL (0.22 ± 0.09 g/L vs. 0.33 ± 0.11 g/L), and lacto-N-triaose 2 (LNT2, 0.03 ± 0.01 g/L vs. 0.16 ± 0.08 g/L) were significantly lower in the S group than in the C group (p < 0.05), while that of 3'-FL was significantly higher in the S group than in the C group (1.35 ± 1.00 g/L vs. 0.41 ± 0.43 g/L, p < 0.05). The diversity and structure of the microbiota in the S and C groups were also significantly different (p < 0.05). Comparative analysis of the microbial communities revealed that Proteobacteria and Firmicutes were the most abundant phyla, in both groups, with the keystone species (Serratia, Streptococcus and Staphylococcus) of breast milk closely interacting with HMOs, including 3'-SL, 6'-SL, and LNT2. In PICRUSt2 functional prediction analysis, the S group exhibited significant reduction in the expression of genes involved in several infectious disease pathways.

Discussion

Our findings support the recognition of human milk as a synbiotic comprising beneficial bacteria and prebiotic HMOs.

Efficient Production of 3'-Sialyllactose Using Escherichia coli

3'-Sialyllactose (3'-SL), a key component of human milk oligosaccharides, provides significant health benefits and immune modulation, and is increasingly used in infant formula and dietary supplements. This study presents a novel approach for the efficient biosynthesis of 3'-SL using Escherichia coli BL21star(DE3)ΔlacZ through genomic integration. We first addressed the issue of metabolic competition by deleting crucial genes, nanA, nanK, nanE, and nanT, that are involved in the degradation of N-acetylneuraminic acid. This strategic gene knockout minimized the flux through competing pathways. The engineered Escherichia coli strain was subsequently transformed with the exogenous genes neuBCA and nST, enabling the de novo synthesis of 3'-SL. A modular metabolic engineering strategy was utilized to optimize the expression of key enzymes within the MSU module, enhancing and balancing the carbon flux distribution. Additionally, a cofactor regeneration strategy was implemented to increase CTP availability, which improved cofactor recycling and fine-tuned the metabolic pathway for maximal 3'-SL production. Transport protein screening was incorporated to further increase the extracellular concentration of 3'-SL, resulting in an unprecedented yield of 56.8 g/L in a 5L bioreactor fermentation, setting a new benchmark in the field.

Absolute quantification of eight human milk oligosaccharides in breast milk to evaluate their concentration profiles and associations with infants' neurodevelopmental outcomes

Human milk oligosaccharides (HMOs) have been positively associated with child neurodevelopment in some cohort studies. However, there is a lack of consistency in the association between HMOs and benefits to infants' brains. Moreover, the quantification methods for HMOs have not yet been standardized. In this study, we developed a quantification method for evaluating eight HMOs (2'-fucosyllactose [2'-FL], 3'-fucosyllactose [3'-FL], 3'-sialyllactose [3'-SL], 6'-sialyllactose [6'-SL], lactosialyltetrasaccharide a [LSTa], lactosialyltetrasaccharide b [LSTb], lactosialyltetrasaccharide c [LSTc], and disialyllacto-N-tetraose [DSLNT]) in breast milk. After validating the method, we applied it to 1-month breast milk samples (n = 150) from the Tohoku Medical Megabank Project Birth and Three-Generation Cohort Study to assess HMO profiles in breast milk and their possible association with changes in head circumference z-score (ΔHCZ) and neurodevelopmental scores of children (as measured by the Ages and Stages Questionnaire, Third Edition). The validation demonstrated that the method had relative standard deviation ≤ 12.7% of precision and 79.5-110.9% of accuracy. Using this method, eight HMO levels (2'-FL, 0-4.74 mg/mL; 3'-FL, 0.02-1.52 mg/mL; 3'-SL, 0.07-0.32 mg/mL; 6'-SL, 0.01-0.70 mg/mL; LSTa, 0.002-0.043 mg/mL; LSTb, 0.02-0.31 mg/mL; LSTc, 0.001-0.47 mg/mL; and DSLNT, 0.09-0.71 mg/mL [min-max, all participants]) and the ratio of low secretors (16.0%) in the Japanese cohort were obtained. The obtained HMO levels in breast milk were subjected to multivariate analysis to screen for HMOs showing a positive association with ΔHCZ and neurodevelopmental scores. The results proposed that ΔHCZ was positively associated with LSTb and 2'-FL levels, whereas neurodevelopmental scores were positively associated with 2'-FL levels (among all participants) and 3'-SL and DSLNT levels (among secretor participants). This study showed that the developed method provides HMO profiles in Japanese breast milk, as well as additional information on the associations between specific HMOs and neurodevelopment, reinforcing the sum of evidence for the role of HMOs in the brain.

Rational modification of Neisseria meningitidis β1,3-N-acetylglucosaminyltransferase for lacto-N-neotetraose synthesis with reduced long-chain derivatives

Lacto-N-neotetraose (LNnT), as a neutral core structure within human milk oligosaccharides (HMOs), has garnered widespread attention due to its exceptional physiological functions. In the process of LNnT synthesis using cellular factory approaches, substrate promiscuity of glycosyltransferases leads to the production of longer oligosaccharide derivatives. Here, rational modification of β1,3-N-acetylglucosaminyltransferase from Neisseria meningitidis (LgtA) effectively decreased the concentration of long-chain LNnT derivatives. Specifically, the optimal β1,4-galactosyltransferase (β1,4-GalT) was selected from seven known candidates, enabling the efficient synthesis of LNnT in Escherichia coli BL21(DE3). Furthermore, the influence of lactose concentration on the distribution patterns of LNnT and its longer derivatives was investigated. The modification of LgtA was conducted with computational assistance, involving alanine scanning based on molecular docking to identify the substrate binding pocket and implementing large steric hindrance on crucial amino acids to obstruct LNnT entry. The implementation of saturation mutagenesis at positions 223 and 228 of LgtA yielded advantageous mutant variants that did not affect LNnT synthesis while significantly reducing the production of longer oligosaccharide derivatives. The most effective mutant, N223I, reduced the molar ratio of long derivatives by nearly 70 %, showcasing promising prospects for LNnT production with diminished byproducts.

Validated Multimethod Approach for Full Characterization of 2'-Fucosyl-d-lactose as an Industrially Produced Human Milk Oligosaccharide

Human milk oligosaccharides are of high interest as active ingredients in infant formulas and dietary food supplements. Full characterization of members of this compound class is challenging due to the intrinsic complexity of byproducts during synthesis by fermentation. Moreover, when method validation is targeted for a regulated environment, a robust chromatographic separation of the highly polar oligosaccharides needs to be addressed, including isomers and compounds relevant for potential product adulteration. We present a combined approach of validated chromatography and NMR spectroscopy, which allows for full mass balancing of industrially produced 2'-fucosyl-d-lactose. A combination of NMR spectroscopy, mass spectrometry, and action IR spectroscopy tackles structural elucidation of monoacetylated species as a new class of byproducts.

Controllable Enzymatic Synthesis of Natural Asymmetric Human Milk Oligosaccharides

Among human milk oligosaccharides (HMOs), linear HMOs are synthesized through mature but varied routes. Although branched HMOs can be synthesized by chemical, enzymatic, or chemoenzymatic methods, these methods cannot be easily applied to the synthesis of asymmetric multiantennary oligosaccharides. Herein, we developed a controllable method to synthesize asymmetric biantennary HMOs. In our synthetic route, GlcNAcβ1,3(GlcN3β1,6)Glaβ1,4Glc was first chemically synthesized as the core tetrasaccharide, which contains β1,6GlcN3 as the "stop" sugar in transferase-catalyzed glycosylation. The desired sugars at the GlcNAcβ1-3Gal arm can be assembled using galactosyltransferase, N-acetylglucosaminyltransferase, and fucosyltransferase. Then, the Staudinger reduction and acetylation were used to transform GlcN3 to GlcNAc and assemble sugars by initiating the "go" process. By manipulating transferase-catalyzed glycosylations, 22 natural asymmetric biantennary oligosaccharides were synthesized.

Biosynthesis of Sialyllacto-N-tetraose c in Engineered Escherichia coli

Human milk oligosaccharides (HMOs) have attracted considerable interest for their vital role in supporting infant health. Among these, sialyllacto-N-tetraose c (LST c), a pentasaccharide with the structure Neu5Ac(α2,6)Gal(β1,4)GlcNAc(β1,3)Gal(β1,4)Glc, stands out due to its critical importance in the development and application of complex HMOs. In this study, we employed multivariate modular metabolic engineering (MMME) to screen for efficient sialyltransferases and balance metabolic fluxes, successfully constructing strains capable of LST c biosynthesis. Additionally, by blocking competing pathway genes, enhancing the supply of UDP-GlcNAc and UDP-Gal precursors, and establishing a CTP cofactor regeneration system, we developed a high-yielding Escherichia coli strain, W15. This strain achieved an LST c titer of 220.9 mg/L in shake flask cultures. In a 3-L fed-batch fermentation, the LST c concentration reached 922.2 mg/L, with a productivity of 10.25 mg/L/h and a specific yield of 38.70 mg/g DCW. This research provides an effective strategy for producing LST c in microbial cell factories.

Human milk oligosaccharide profiles remain unaffected by maternal pre-pregnancy body mass index in an observational study

Human milk oligosaccharides (HMOs) are important carbohydrates in human milk that infants cannot digest, acting as prebiotics linked to infant health. The risk of childhood obesity increases with maternal obesity, potentially mediated through the gut microbiota affected by the available HMOs. Studies on whether maternal obesity affects HMO abundance, yield conflicting results. This study aimed to investigate the HMO profile and its association with maternal obesity measured by pre-pregnancy body mass index (BMI) and infant anthropometrics. The results were discussed in the context of existing literature. 90 human milk samples were collected at 3 months postpartum from mothers in three BMI-groups: 32 normal weight (BMI: 18.5-24.99 kg/m2), 34 overweight (BMI: 25-30 kg/m2), and 24 obese (BMI > 30 kg/m2). The samples were analyzed using nano liquid chromatography chip quadrupole time-of-flight mass spectrometry yielding 51 HMO structures and isomers. Their peak areas were integrated and normalized to determine relative abundances. Univariate and multivariate analysis showed associations between relative HMO abundance and donors' secretor status and specific infant anthropometric variables, but not with maternal pre-pregnancy BMI. This study does not support the hypothesis that maternal overweight influences the HMO profile and highlights the importance of reporting results despite absence of significant correlations.

Effects of Human Milk Oligosaccharide 2'-Fucosyllactose Ingestion on Weight Loss and Markers of Health

BACKGROUND

2'-Fucosyllactose (2'-FL) is an oligosaccharide contained in human milk and possesses prebiotic and anti-inflammatory effects, which may alleviate skeletal muscle atrophy under caloric restriction. This study evaluated the impacts of 12 weeks of 2'-FL supplementation in conjunction with exercise (10,000 steps/day, 5 days/week) and energy-reduced (-300 kcals/day) dietary interventions on changes in body composition and health-related biomarkers.

METHODS

A total of 41 overweight and sedentary female and male participants (38.0 ± 13 years, 90.1 ± 15 kg, 31.6 ± 6.6 kg/m2, 36.9 ± 7% fat) took part in a randomized, double-blind, and placebo-controlled study. The participants underwent baseline assessments and were then assigned to ingest 3 g/day of a placebo (PLA) or Momstamin 2'-F while initiating the exercise and weight-loss program. Follow-up tests were performed after 6 and 12 weeks. Data were analyzed using general linear model statistics with repeated measures and mean changes from baseline values with 95% confidence intervals (CIs).

RESULTS

No group × time × sex interaction effects were observed, so group × time effects are reported. Participants in both groups saw comparable reductions in weight. However, those with 2'-FL demonstrated a significantly greater reduction in the percentage of body fat and less loss of the fat-free mass. Additionally, there was evidence that 2'-FL supplementation promoted more favorable changes in resting fat oxidation, peak aerobic capacity, IL-4, and platelet aggregation, with some minimal effects on the fermentation of short-chain fatty acids and monosaccharides in fecal samples. Moreover, participants' perceptions regarding some aspects of the functional capacity and ratings of the quality of life were improved, and the supplementation protocol was well tolerated, although a small, but significant, decrease in BMC was observed.

CONCLUSIONS

The results support contentions that dietary supplementation of 2'-FL (3 g/d) can promote fat loss and improve exercise- and diet-related markers of health and fitness in overweight sedentary individuals initiating an exercise and weight-loss program. Further research is needed to explore the potential health benefits of 2'-FL supplementation in both healthy and elderly individuals (Registered clinical trial #NCT06547801).

Heterologous expression of a novel galactose-1-phosphate uridylyltransferase from Thermodesulfatator indicus and its application for bioproduction of Gal-β-1,4-GlcNAc-X

Nucleotide sugars (UDP-Sugars) are essential for the production of polysaccharides and glycoconjugates utilized in medicines, cosmetics, and food industries. The enzyme Galactose-1-phosphate uridylyltransferase (GalU; EC 2.7.7.12) is responsible for the synthesis of UDP-galactose from α-d-galactose-1-phosphate (Gal-1P) and UTP. A novel bacterial GalU (TiGalU) encoded from a thermophilic bacterium, Thermodesulfatator indicus, was successfully purified using the Ni-NTA column after being expressed in Escherichia coli. The optimal pH for recombinant TiGalU was determined to be 5.5. The optimum temperature of the enzyme was 45 °C. The activity of TiGalU was not dependent on Mg2+ and was strongly inhibited by SDS. When coupled with galactose kinase (GALK1) and β-1,4-galactosyltransferase 1 (B4GALT1), the enzyme enabled the one-pot synthesis of Gal-β-1,4-GlcNAc-X by utilizing galactose and UTP as substrates. This study reported the in vitro biosynthesis of Gal-β-1,4-GlcNAc-X for the first time, providing an environmentally friendly way to biosynthesis glycosides and other polysaccharides.

A comparative study of the substrate preference of the sialidases, CpNanI, HpNanH, and BbSia2 towards 2-Aminobenzamide-labeled 3'-Sialyllactose, 6'-Sialyllactose, and Sialyllacto-N-tetraose-b

Sialidases catalyze the removal of terminal sialic acids from sialylated biomolecules, and their substrate preference is frequently indicated in terms of the glycosidic linkages cleaved (α2-3, α2-6, and α2-8) without mention of the remaining sub-terminal reducing-end saccharide moieties. Many human gut commensal and pathogenic bacteria secrete sialidases to forage for sialic acids, which are then utilized as an energy source or assimilated into membrane/capsular structural components. Infant gut commensals similarly utilize sialylated human milk oligosaccharides containing different glycosidic linkages. Here, we have studied the preference of the bacterial sialidases, BbSia2 from Bifidobacterium bifidum, CpNanI from Clostridium perfringens, and HpNanH from Glaesserella parasuis, for the glycosidic linkages, Siaα2-3Gal, Siaα2-6Gal, and Siaα2-6GlcNAc, by employing 2-Aminobenzamide-labeled human milk oligosaccharides, 3'-Sialyllactose (3'-SL), 6'-Sialyllactose (6'-SL), and Sialyllacto-N-tetraose-b (LSTb), respectively, as proxies for these glycosidic linkages. BbSia2, CpNanI, and HpNanH hydrolyzed these three oligosaccharides with the glycosidic linkage preferences, 3'-SL (Siaα2-3Gal) ≥ LSTb (Siaα2-6GlcNAc) ≥ 6'-SL (Siaα2-6Gal), 3'-SL (Siaα2-3Gal) ≥ 6'-SL (Siaα2-6Gal) > LSTb (Siaα2-6GlcNAc), and 3'-SL (Siaα2-3Gal) ≥ 6'-SL (Siaα2-6Gal) > LSTb (Siaα2-6GlcNAc), respectively. Our finding suggests that sub-terminal reducing-end saccharide moieties can profoundly influence the substrate preference of sialidases, and advocates for the characterization and indication of the substrate preference of sialidases in terms of both the glycosidic linkage and the sub-terminal reducing-end saccharide moiety.

Is it possible to obtain substitutes for human milk oligosaccharides from bovine milk, goat milk, or other mammal milks?

Considering the current level of chemical and biological synthesis technology, it was a sensible selection to obtain milk oligosaccharides (MOs) from other mammals as the potential substitute for human MOs (HMOs) that possessed various structural features in the infant formula. Through a comprehensive analysis of the content, structure, and function of MOs in six distinct varieties of mammal milk, it has been shown that goat milk was the most suitable material for the preparation as a human milk substitute. Goat MOs (GMOs) had a relatively high content and diverse structural features compared to those found in other mammalian milks. The concentration of GMOs in colostrum ranged from 60 to 350 mg/L, whereas in mature milk, it ranged from 200 to 24,00 mg/L. The acidic oligosaccharides in goat milk have attracted considerable attention due to their closeness in acidic content and structural diversity with HMOs. Simultaneously, it was discovered that some structures, like N-glycolylneuraminic acid, were found to have a certain content in GMOs and served essential functional properties. Moreover, studies focused on the extraction of MOs from goat milk indicated that the production of GMOs on an industrial scale was viable. Furthermore, it is imperative to do further study on GMOs to enhance the preparation process, discover of new MOs structures and bioactivity evaluation, which will contribute to the development of both the commercial production of MOs and the goat milk industry.

Genetic and environmental factors shaping goat milk oligosaccharide composition

Oligosaccharides (OS) in milk have been suggested to influence the health and development of the newborn by promoting growth of beneficial gut bacteria, stimulating brain development, and enhancing immune functions. Goat milk is a natural source of specific OS, which could be a potential beneficial ingredient for infant formula. In this study, goat milk oligosaccharide (gMOS) content from approximately 1,000 dairy goats across 18 commercial farms was studied. A genomic relationship matrix was used to unravel genetic and environmental factors shaping gMOS content. The most abundant gMOS identified was 3'-NGL, with a concentration of 32.05 mg/kg, while 3-FL exhibited the lowest concentration at 1.85 mg/kg. Acidic OS had a notably higher content (81.67 mg/kg) than neutral OS (24.88 mg/kg). High variability in gMOS content was observed among individual goats, which could for a large extent be attributed to genetic differences. Heritability estimates ranged from 31% for 3'-GL to 85% for 3-FL. High positive genetic correlations (>0.57) were estimated between 3'-SL and 6'-SL, and between 6'-GL and 3'-GL. The contribution of differences between farms to variation in milk OS content varied from 3% for 3'-NGL to 45% for 6'-SL. While gMOS like 3'-GL, 6'-GL, and 6'-NGL, were significantly influenced by systematic environmental factors such as the lactation stage, the impact of these factors was relatively minor compared with the importance of genetic and farm effects. This research, which stands out due to its relatively large sample size, underscores the pivotal role of genetics, and to a smaller extent farm practices like feed ration, in determining gMOS composition.

Modifiable and Non-Modifiable Factors That Affect Human Milk Oligosaccharides Composition

Human milk, the gold standard in infant nutrition, is a unique fluid that provides essential nutrients such as lactose, lipids, proteins, and free oligosaccharides. While its primary role is nutritional, it also protects against pathogens. This protection mainly comes from immunoglobulins, with human milk oligosaccharides (HMOs) providing additional support by inhibiting pathogen binding to host cell ligands. The prebiotic and immune-modulatory activity of HMOs strongly depends on their structure. Over 200 individual structures have been identified so far, with the composition varying significantly among women. The structure and composition of HMOs are influenced by factors such as the Lewis blood group, secretor status, and the duration of nursing. HMO profiles are heavily influenced by maternal phenotypes, which are defined based on the expression of two specific fucosyltransferases. However, recent data have shown that HMO content can be modified by various factors, both changeable and unchangeable, including diet, maternal age, gestational age, mode of delivery, breastfeeding frequency, and race. The first part of this overview presents the historical background of these sugars and the efforts by scientists to extract them using the latest chromatography methods. The second part is divided into subchapters that examine modifiable and non-modifiable factors, reviewing the most recent articles on HMO composition variations due to specific reasons and summarizing potential future challenges in conducting these types of studies.

Recent advances of 3-fucosyllactose in health effects and production

Human milk oligosaccharides (HMOs) have been recognized as gold standard for infant development. 3-Fucosyllactose (3-FL), being one of the Generally Recognized as Safe HMOs, represents a core trisaccharide within the realm of HMOs; however, it has received comparatively less attention in contrast to extensively studied 2'-fucosyllactose. The objective of this review is to comprehensively summarize the health effects of 3-FL, including its impact on gut microbiota proliferation, antimicrobial effects, immune regulation, antiviral protection, and brain maturation. Additionally, the discussion also covers the commercial application and regulatory approval status of 3-FL. Lastly, an organized presentation of large-scale production methods for 3-FL aims to provide a comprehensive guide that highlights current strategies and challenges in optimization.

Ameliorating effect of 2'-fucosyllactose and 6'-sialyllactose on lipopolysaccharide-induced intestinal inflammation

Human milk oligosaccharides (HMO) affect gut microbiota during neonatal development, particularly with respect to the immune system. Bovine milk-based infant formulas have low oligosaccharide contents. Thus, efforts to fortify infant formulas with HMO are being undertaken. Two major HMO, 2'-fucosyllactose (2'-FL) and 6'-sialyllactose (6'-SL), exert anti-inflammatory effects; however, the associations between anti-inflammatory effects induced by 2'-FL and 6'-SL cotreatment and gut microbiota composition and metabolite modulation remain unclear. Therefore, in this study, we evaluated the effects of a mixture of these HMO. To determine the optimal HMO ratio for anti-inflammatory effects and elucidate its mode of action, LPS-induced inflammatory HT-29 epithelial cells and intestinal-inflamed suckling mice were treated with various mixtures of 2'-FL and 6'-SL. A 2'-FL:6'-SL ratio of 5:1 was identified as the most effective pretreatment HMO mixture in vitro; thus, this ratio was selected and used for low-, middle-, and high-dose treatments for subsequent in vivo studies. In vivo, high-dose HMO treatment restored LPS-induced inflammation symptoms, such as BW loss, colon length reduction, histological structural damage, and intestinal gene expression related to inflammatory responses. High-dose HMO was the only treatment that modulated the major phyla Bacteroidetes and Firmicutes and the genera Ihubacter, Mageeibacillus, and Saccharofermentans. These changes in microbial composition were correlated with intestinal inflammation-related gene expression and short-chain fatty acid production. To our knowledge, our study is the first to report the effects of Ihubacter, Mageeibacillus, and Saccharofermentans on short-chain fatty acid levels, which can subsequently affect inflammatory cytokine and tight junction protein levels. Conclusively, the HMO mixture exerted anti-inflammatory effects through changes in microbiota and metabolite production. These findings suggest that supplementation of infant formula with HMO may benefit formula-fed infants by forming unique microbiota contributing to neonatal development.

3-Fucosyllactose-mediated modulation of immune response against virus infection

Viral pathogens, particularly influenza and SARS-CoV-2, pose a significant global health challenge. Given the immunomodulatory properties of human milk oligosaccharides, in particular 2'-fucosyllactose and 3-fucosyllactose (3-FL), we investigated their dietary supplementation effects on antiviral responses in mouse models. This study revealed distinct immune modulations induced by 3-FL. RNA-sequencing data showed that 3-FL increased the expression of interferon receptors, such as Interferon Alpha and Beta Receptor (IFNAR) and Interferon Gamma Receptor (IFNGR), while simultaneously downregulating interferons and interferon-stimulated genes, an effect not observed with 2'-fucosyllactose supplementation. Such modulation enhanced antiviral responses in both cell culture and animal models while attenuating pre-emptive inflammatory responses. Nitric oxide concentrations in 3-FL-supplemented A549 cells and mouse lung tissues were elevated exclusively upon infection, reaching 5.8- and 1.9-fold increases over control groups, respectively. In addition, 3-FL promoted leukocyte infiltration into the site of infection upon viral challenge. 3-FL supplementation provided protective efficacy against lethal influenza challenge in mice. The demonstrated antiviral efficacy spanned multiple influenza strains and extended to SARS-CoV-2. In conclusion, 3-FL is a unique immunomodulator that helps protect the host from viral infection while suppressing inflammation prior to infection.

Combinatorial Engineering of Escherichia coli for Enhancing 3-Fucosyllactose Production

3-Fucosyllactose (3-FL) is an important fucosylated human milk oligosaccharide (HMO) with biological functions such as promoting immunity and brain development. Therefore, the construction of microbial cell factories is a promising approach to synthesizing 3-FL from renewable feedstocks. In this study, a combinatorial engineering strategy was used to achieve efficient de novo 3-FL production in Escherichia coli. α-1,3-Fucosyltransferase (futM2) from Bacteroides gallinaceum was introduced into E. coli and optimized to create a 3-FL-producing chassis strain. Subsequently, the 3-FL titer increased to 5.2 g/L by improving the utilization of the precursor lactose and down-regulating the endogenous competitive pathways. Furthermore, a synthetic membraneless organelle system based on intrinsically disordered proteins was designed to spatially regulate the pathway enzymes, producing 7.3 g/L 3-FL. The supply of the cofactors NADPH and GTP was also enhanced, after which the 3-FL titer of engineered strain E26 was improved to 8.2 g/L in a shake flask and 10.8 g/L in a 3 L fermenter. In this study, we developed a valuable approach for constructing an efficient 3-FL-producing cell factory and provided a versatile workflow for other chassis cells and HMOs.

Human Milk Oligosaccharides and Respiratory Syncytial Virus Infection in Infants

In infants worldwide, respiratory syncytial virus (RSV) is the leading cause of lower respiratory infections, including bronchiolitis, which is a major source of infant mortality. Bronchiolitis is the most common lower respiratory infection and the major cause of hospitalization in the first 6 mo of life. Infant responses to RSV infection are highly diverse, with symptoms varying from asymptomatic or mild to so severe as to require mechanical ventilation. Breastfed infants present a lower incidence and less severe forms of RSV lower respiratory infections. Among the multitude of human milk bioactive compounds, human milk oligosaccharides (hMOSs) are strong candidates for having a protective effect against RSV. hMOS reduces the viral load and the inflammatory signaling in cultured RSV-infected respiratory human cells. In addition to this direct effect, indirect mechanisms, notably gut microbiota composition and metabolism, have been proposed to mediate the protective effect of hMOS. Intake of infant formula containing synthetic hMOS has been shown to increase Bifidobacterium abundance and that of its metabolites, especially acetate, in infant feces and to reduce lower respiratory tract infections during the first year of life. Breastfeeding and the use of hMOS are promising approaches to protect against and treat RSV disease. Here, we review current evidence on the role of hMOS with regard to RSV infection and disease, attending to knowledge gaps and future research directions.

The Role of Maternal Secretor Status and Human Milk Oligosaccharides on Early Childhood Development: A Systematic Review and Meta-Analysis

Background: Breast milk is the gold standard of infant nutrition, delivering nutrients and bioactive molecules as needed to support optimal infant growth and cognitive development. Increasing evidence links human milk oligosaccharides (HMOs) to these early childhood development milestones. Aims: To summarize and synthesize the evidence relating to HMOs and infant brain development, physical growth, and cognitive development. In addition, HMO concentrations in secretor and nonsecretor mothers were compared via a meta-analysis. Study Design: A systematic review and meta-analysis were carried out in accordance with the PRISMA statement. This review used three databases (PubMed, Scopus, and Web of Science) and was limited to English-language articles published between 2000 and June 30, 2023. Results: The initial searches yielded 245 articles, 27 of which were included in the systematic review and 12 in the meta-analysis. The meta-analysis revealed a substantial between-study heterogeneity, I2 = 97.3%. The pooled effect was 0.21 (95% CI: -0.41 to 0.83; p = 0.484), indicating that secretors had higher HMO concentrations, although this difference was not statistically significant. At one month of age, 2'FL, 3FL, and 3'SL play an important role in brain maturation and thus play a critical role in cognitive development. Secretors produce higher concentrations of 2'FL and 3'SL, explaining the benefits to infants of secretor mothers. Growth velocity was correlated to fucosylated and sialylated HMO concentrations, with lower concentrations linked to stunting. Conclusions: According to evidence from the systematically reviewed articles, HMOs are essential for a child's early development, but the extent to which they have an impact depends on maternal secretor status.

Engineered plants provide a photosynthetic platform for the production of diverse human milk oligosaccharides

Human milk oligosaccharides (HMOs) are a diverse class of carbohydrates which support the health and development of infants. The vast health benefits of HMOs have made them a commercial target for microbial production; however, producing the approximately 200 structurally diverse HMOs at scale has proved difficult. Here we produce a diversity of HMOs by leveraging the robust carbohydrate anabolism of plants. This diversity includes high-value and complex HMOs, such as lacto-N-fucopentaose I. HMOs produced in transgenic plants provided strong bifidogenic properties, indicating their ability to serve as a prebiotic supplement with potential applications in adult and infant health. Technoeconomic analyses demonstrate that producing HMOs in plants provides a path to the large-scale production of specific HMOs at lower prices than microbial production platforms. Our work demonstrates the promise in leveraging plants for the low-cost and sustainable production of HMOs.

Recent Advances in the Microbial Production of Human Milk Oligosaccharides

Human milk oligosaccharides (HMOs) are naturally occurring, non-digestible sugars found in human milk. They have recently become a popular target for industrial synthesis due to their positive effects on the developing gut microbiome and immune system of infants. Microbial synthesis has shown great promise in driving down the cost of these sugars and making them more available for consumers and researchers. The application of common metabolic engineering techniques such as gene knockouts, gene overexpression, and expression of exogenous genes has enabled the rational design of whole-cell biocatalysts which can produce increasingly complex HMOs. Herein, we discuss how these strategies have been applied to produce a variety of sugars from sialylated to complex fucosylated HMOs. With increased availability of HMOs, more research can be done to understand their beneficial effects.

Synthesis of fucosyllactose using α-L-fucosidases GH29 from infant gut microbial metagenome

Fucosyl-oligosaccharides (FUS) provide many health benefits to breastfed infants, but they are almost completely absent from bovine milk, which is the basis of infant formula. Therefore, there is a growing interest in the development of enzymatic transfucosylation strategies for the production of FUS. In this work, the α-L-fucosidases Fuc2358 and Fuc5372, previously isolated from the intestinal bacterial metagenome of breastfed infants, were used to synthesize fucosyllactose (FL) by transfucosylation reactions using p-nitrophenyl-α-L-fucopyranoside (pNP-Fuc) as donor and lactose as acceptor. Fuc2358 efficiently synthesized the major fucosylated human milk oligosaccharide (HMO) 2'-fucosyllactose (2'FL) with a 35% yield. Fuc2358 also produced the non-HMO FL isomer 3'-fucosyllactose (3'FL) and traces of non-reducing 1-fucosyllactose (1FL). Fuc5372 showed a lower transfucosylation activity compared to Fuc2358, producing several FL isomers, including 2'FL, 3'FL, and 1FL, with a higher proportion of 3'FL. Site-directed mutagenesis using rational design was performed to increase FUS yields in both α-L-fucosidases, based on structural models and sequence identity analysis. Mutants Fuc2358-F184H, Fuc2358-K286R, and Fuc5372-R230K showed a significantly higher ratio between 2'FL yields and hydrolyzed pNP-Fuc than their respective wild-type enzymes after 4 h of transfucosylation. The results with the Fuc2358-F184W and Fuc5372-W151F mutants showed that the residues F184 of Fuc2358 and W151 of Fuc5372 could have an effect on transfucosylation regioselectivity. Interestingly, phenylalanine increases the selectivity for α-1,2 linkages and tryptophan for α-1,3 linkages. These results give insight into the functionality of the active site amino acids in the transfucosylation activity of the GH29 α-L-fucosidases Fuc2358 and Fuc5372. KEY POINTS: Two α-L-fucosidases from infant gut bacterial microbiomes can fucosylate glycans Transfucosylation efficacy improved by tailored point-mutations in the active site F184 of Fuc2358 and W151 of Fuc5372 seem to steer transglycosylation regioselectivity.

Effects of 2'-fucosyllactose on the viability of starter cultures and Bifidobacterium strains of human origin in yogurt during refrigerated storage

2'-Fucosyllactose (2'-FL) is postulated to provide health benefits and promote the growth of probiotics. This work was undertaken to study the effects of 2'-FL on the viability of starter cultures and Bifidobacterium strains of human origin in yogurt during refrigerated storage. Yogurts were produced containing 2'-FL (0 or 2 g/L) and Bifidobacterium strains of human origin (Bifidobacterium longum subsp. longum BB536 or Bifidobacterium longum subsp. infantis ATCC 15697) at a concentration of at least 109 CFU/mL. All yogurts were stored at 4°C for 5 weeks. Results showed that 2'-FL was stable in yogurts for at least 5 weeks of cold storage, and the addition of 2'-FL did not significantly alter yogurt fermentation parameters, associated metabolites, and the viability of mixed yogurt starter cultures and Bifidobacterium strains (p > 0.05). The addition of bifidobacteria had a negative impact (p < 0.05) on the survival rate of starter cultures, Streptococcus thermophilus and Lactobacillus delbureckii subsp. bulgaricus. Meanwhile, it is difficult to maintain a high survival rate of bifidobacteria in final yogurt products, and the addition of 2'-FL could not enhance the viability of bifidobacteria. B. longum BB536 survived at a level higher than 106 CFU/g for 28 days, while B. infantis ATCC15697 maintained this level for only 7 days. In summary, this study has shown the impact of 2'-FL and bifidobacterial species on yogurt properties, and results suggest that it is promising to use 2'-FL in yogurt products as a prebiotic. PRACTICAL APPLICATION: Yogurt is known for its beneficial effects on human health and nutrition. This study reported the production of symbiotic yogurt containing bifidobacteria and 2'-fucosyllactose (2'-FL) as a functional food for specified health uses. The viability of yogurt starter cultures and probiotic bifidobacterial strains was analyzed in this study. Moreover, this research demonstrated that 2'-FL could be added to yogurt without affecting the characteristics of yogurt significantly.

Microbiota from human infants consuming secretors or non-secretors mothers' milk impacts the gut and immune system in mice

Maternal secretor status is one of the determinants of human milk oligosaccharides (HMOs) composition, which, in turn, influences the gut microbiota composition of infants. To understand if this change in gut microbiota impacts immune cell composition, intestinal morphology, and gene expression, 21-day-old germ-free C57BL/6 mice were transplanted with fecal microbiota from infants whose mothers were either secretors (SMM) or non-secretors (NSM) or from infants consuming dairy-based formula (MFM). For each group, one set of mice was supplemented with HMOs. HMO supplementation did not significantly impact the microbiota diversity; however, SMM mice had a higher abundance of genus Bacteroides, Bifidobacterium, and Blautia, whereas, in the NSM group, there was a higher abundance of Akkermansia, Enterocloster, and Klebsiella. In MFM, gut microbiota was represented mainly by Parabacteroides, Ruminococcaceae_unclassified, and Clostrodium_sensu_stricto. In mesenteric lymph node, Foxp3+ T cells and innate lymphoid cells type 2 were increased in MFM mice supplemented with HMOs, while in the spleen, they were increased in SMM + HMOs mice. Similarly, serum immunoglobulin A was also elevated in MFM + HMOs group. Distinct global gene expression of the gut was observed in each microbiota group, which was enhanced with HMOs supplementation. Overall, our data show that distinct infant gut microbiota due to maternal secretor status or consumption of dairy-based formula and HMO supplementation impacts immune cell composition, antibody response, and intestinal gene expression in a mouse model.

IMPORTANCE

Early life factors like neonatal diet modulate gut microbiota, which is important for the optimal gut and immune function. One such factor, human milk oligosaccharides (HMOs), the composition of which is determined by maternal secretor status, has a profound effect on infant gut microbiota. However, how the infant gut microbiota composition determined by maternal secretor status or consumption of infant formula devoid of HMOs impacts infant intestinal ammorphology, gene expression, and immune signature is not well explored. This study provides insights into the differential establishment of infant microbiota derived from infants fed by secretor or non-secretor mothers milk or those consuming infant formula and demonstrates that the secretor status of mothers promotes Bifidobacteria and Bacteroides sps. establishment. This study also shows that supplementation of pooled HMOs in mice changed immune cell composition in the spleen and mesenteric lymph nodes and immunoglobulins in circulation. Hence, this study highlights that maternal secretor status has a role in infant gut microbiota composition, and this, in turn, can impact host gut and immune system.

RM, Acra SA, Townsend SD, Yan F. A human milk oligosaccharide prevents intestinal inflammation in adulthood via modulating gut microbial metabolism

Observational evidence suggests that human milk oligosaccharides (HMOs) promote the growth of commensal bacteria in early life and adulthood. However, the mechanisms by which HMOs benefit health through modulation of gut microbial homeostasis remain largely unknown. 2'-fucosyllactose (2'-FL) is the most abundant oligosaccharide in human milk and contributes to the essential health benefits associated with human milk consumption. Here, we investigated how 2'-FL prevents colitis in adulthood through its effects on the gut microbial community. We found that the gut microbiota from adult mice that consumed 2'-FL exhibited an increase in abundance of several health-associated genera, including Bifidobacterium and Lactobacillus. The 2'-FL-modulated gut microbial community exerted preventive effects on colitis in adult mice. By using Bifidobacterium infantis as a 2'-FL-consuming bacterial model, exploratory metabolomics revealed novel 2'-FL-enriched secretory metabolites by Bifidobacterium infantis, including pantothenol. Importantly, pantothenate significantly protected the intestinal barrier against oxidative stress and mitigated colitis in adult mice. Furthermore, microbial metabolic pathway analysis identified 26 dysregulated metabolic pathways in fecal microbiota from patients with ulcerative colitis, which were significantly regulated by 2'-FL treatment in adult mice, indicating that 2'-FL has the potential to rectify dysregulated microbial metabolism in colitis. These findings support the contribution of the 2'-FL-shaped gut microbial community and bacterial metabolite production to the protection of intestinal integrity and prevention of intestinal inflammation in adulthood.IMPORTANCEAt present, neither basic research nor clinical studies have revealed the exact biological functions or mechanisms of action of individual oligosaccharides during development or in adulthood. Thus, it remains largely unknown whether human milk oligosaccharides could serve as effective therapeutics for gastrointestinal-related diseases. Results from the present study uncover 2'-FL-driven alterations in bacterial metabolism and identify novel B. infantis-secreted metabolites following the consumption of 2'-FL, including pantothenol. This work further demonstrates a previously unrecognized role of pantothenate in significantly protecting the intestinal barrier against oxidative stress and mitigating colitis in adult mice. Remarkably, 2'-FL-enhanced bacterial metabolic pathways are found to be dysregulated in the fecal microbiota of ulcerative colitis patients. These novel metabolic pathways underlying the bioactivities of 2'-FL may lay a foundation for applying individual oligosaccharides for prophylactic intervention for diseases associated with impaired intestinal homeostasis.

Potential biological functions and future perspectives of sialylated milk oligosaccharides

Sialyllactoses (SLs) primarily include sialylated human milk oligosaccharides (HMOs) and bovine milk oligosaccharides (BMOs). First, the safety assessment of 3'-sialyllactose (3'-SL) and 6'-sialyllactose (6'-SL) revealed low toxicity in various animal models and human participants. SLs constitute a unique milk component, highlighting the essential nutrients and bioactive components crucial for infant development, along with numerous associated health benefits for various diseases. This review explores the safety, biosynthesis, and potential biological effects of SLs, with a specific focus on their influence across various physiological systems, including the gastrointestinal system, immune disorders, rare genetic disorders (such as GNE myopathy), cancers, neurological disorders, cardiovascular diseases, diverse cancers, and viral infections, thus indicating their therapeutic potential.

Human milk oligosaccharide composition following supplementation with folic acid vs (6S)-5-methyltetrahydrofolic acid during pregnancy and mediation by human milk folate forms

Supplementation with folic acid versus (6S)-5-methyltetrahydrofolic acid (5-MTHF) results in different folate forms in human milk, with folic acid increasing unmetabolized folic acid (UMFA) at the expense of reduced folate forms. It is unknown whether folate forms present in human milk have further effects on human milk composition, such as human milk oligosaccharide (HMO) concentrations. We randomized 60 pregnant women in Canada to 0.6 mg/day folic acid or (6S)-5-MTHF. Human milk folate forms (LC-MS/MS) and nineteen HMOs (HPLC) were quantified at 1 week postpartum. Linear regression and causal mediation analysis were used to evaluate the effect of folate supplementation on HMO concentrations, and possible mediation by concentrations of UMFA and reduced folate forms in human milk (controlling for secretor status and parity). HMO concentrations were not different between groups, with no evidence of mediation by reduced folate forms; however, increased UMFA was associated with reduced concentrations of total HMOs and 3'-sialyllactose.

Metabolic Engineering of Escherichia coli for High-Titer Biosynthesis of 3'-Sialyllactose

3'-Sialyllactose (3'-SL) is among the foremost and simplest sialylated breast milk oligosaccharides. In this study, an engineered Escherichia coli for high-titer 3'-SL biosynthesis was developed by introducing a multilevel metabolic engineering strategy, including (1) the introduction of precursor CMP-Neu5Ac synthesis pathway and high-performance α2,3-sialyltransferase (α2,3-SiaT) genes into strain BZ to achieve de novo synthesis of 3'-SL; (2) optimizing the expression of glmS-glmM-glmU involved in the UDP-GlcNAc and CMP-Neu5Ac synthesis pathways, and constructing a glutamine cycle system, balancing the precursor pools; (3) analysis of critical intermediates and inactivation of competitive pathway genes to redirect carbon flux to 3'-SL biosynthesis; and (4) enhanced catalytic performance of rate-limiting enzyme α2,3-SiaT by RBS screening, protein tag cloning. The final strain BZAPKA14 yielded 9.04 g/L 3'-SL in a shake flask. In a 3 L bioreactor, fed-batch fermentation generated 44.2 g/L 3'-SL, with an overall yield and lactose conversion of 0.53 g/(L h) and 0.55 mol 3'-SL/mol, respectively.

Selective microbial production of lacto-N-fucopentaose I in Escherichia coli using engineered α-1,2-fucosyltransferases

Lacto-N-fucopentaose I (LNFP I) is the second most abundant fucosylated human milk oligosaccharide (HMO) in breast milk after 2'-fucosyllactose (2'-FL). Studies have reported that LNFP I exhibits antimicrobial activity against group B Streptococcus and antiviral effects against Enterovirus and Norovirus. Microbial production of HMOs by engineered Escherichia coli is an attractive, low-cost process, but few studies have investigated production of long-chain HMOs, including the pentasaccharide LNFP I. LNFP I is synthesized by α1,2-fucosyltransfer reaction to the N-acetylglucosamine moiety of the lacto-N-tetraose skeleton, which is catalyzed by α1,2-fucosyltransferase (α1,2-FucT). However, α1,2-FucTs competitively transfer fucose to lactose, resulting in formation of the byproduct 2'-FL. In this study, we constructed LNFP I-producing strains of E. coli with various α1,2-fucTs, and observed undesired 2'-FL accumulation during fed-batch fermentation, although, in test tube assays, some strains produced LNFP I without 2'-FL. We hypothesized that promiscuous substrate selectivity of α1,2-FucT was responsible for 2'-FL production. Therefore, to decrease the formation of byproduct 2'-FL, we designed 15 variants of FsFucT from Francisella sp. FSC1006 by rational and semi-rational design approaches. Five of these variants of FsFucT surpassed a twofold reduction in 2'-FL production compared with wild-type FsFucT while maintaining comparable levels of LNFP I production. These designs encompassed substitutions in either a loop region of the enzyme (residues 154-171), or in specific residues (Q7, H162, and L164) that influence substrate binding either directly or indirectly. In particular, the E. coli strain that expressed FsFucT_S3 variants, with a substituted loop region (residues 154-171) forming an α-helix structure, achieved an accumulation of 19.6 g/L of LNFP I and 0.04 g/L of 2'-FL, while the E. coli strain expressing the wild-type FsFucT accumulated 12.2 g/L of LNFP I and 5.85 g/L of 2'-FL during Fed-bach fermentation. Therefore, we have successfully demonstrated the selective and efficient production of the pentasaccharide LNFP I without the byproduct 2'-FL by combining protein engineering of α1,2-FucT designed through in silico structural modeling of an α1,2-FucT and docking simulation with various ligands, with metabolic engineering of the host cell.

Determination of Seven Human Milk Oligosaccharides (HMOs) in Infant Formula and Adult Nutritionals: First Action 2022.07

BACKGROUND

Human milk oligosaccharides (HMOs) are important components of breast milk and may be responsible for some of the benefits of breastfeeding, including resistance to infections and the development of a healthy gut microbiota. Selected HMOs are now available for addition to infant formula, and suitable methods to control the dosing rate are needed.

OBJECTIVE

To develop and validate a suitable method for the analysis of HMOs in infant formula.

METHOD

A method was developed for the determination of seven human milk oligosaccharides (2'-fucosyllactose, 3-fucosyllactose, 3'-sialyllactose, 6'-sialyllactose (6'SL), 2',3-difucosyllactose, lacto-N-tetraose (LNT), lacto-N-neotetraose (LNnT)) in infant formula and adult nutritionals. The oligosaccharides are labeled at their reducing end with 2-aminobenzamide, separated by liquid chromatography and detected using a fluorescence detector. Maltodextrins are enzymatically hydrolyzed before analysis to prevent potential interference; likewise, an optional β-galactosidase treatment can be used to remove β-galactooligosaccharides. Fructooligosaccharides or polydextrose do not generally interfere with the analysis.

RESULTS

The method has been validated in a single laboratory on infant formula and adult nutritionals. The seven HMOs were spiked into eight matrixes at three or four spike levels, giving a total of 176 data points. Recoveries were in the range of 90.9-109% in all cases except at the lowest spike level in one matrix (elemental formula), where the LNT recovery was 113%, the LNnT recovery was 111%, and the 6'SL recovery was 121%. Relative repeatabilities (RSD(r)) were in the range of 0.1-4.2%. The performance is generally within the requirements outlined in the Standard Method Performance Requirements (SMPR®) published by AOAC INTERNATIONAL.

CONCLUSIONS

The method developed is suitable for the determination of seven HMOs in infant formula and demonstrated good performance during single-laboratory validation.

HIGHLIGHTS

A method has been developed that is suitable for the determination of seven HMOs in infant formula.

Influence of microbially fermented 2´-fucosyllactose on neuronal-like cell activity in an in vitro co-culture system

Scope

2´-Fucosyllactose (2´-FL), the most abundant oligosaccharide in human milk, plays an important role in numerous biological functions, including improved learning. It is not clear, however, whether 2´-FL or a cleavage product could influence neuronal cell activity. Thus, we investigated the effects of 2´-FL, its monosaccharide fucose (Fuc), and microbial fermented 2´-FL and Fuc on the parameters of neuronal cell activity in an intestinal-neuronal transwell co-culture system in vitro.

Methods

Native 13C-labeled 2´-FL and 13C-Fuc or their metabolites, fermented with Bifidobacterium (B.) longum ssp. infantis and B. breve, which were taken from the lag-, log- and stationary (stat-) growth phases of batch cultures, were applied to the apical compartment of the co-culture system with Caco-2 cells representing the intestinal layer and all-trans-retinoic acid-differentiated SH-SY5Y (SH-SY5YATRA) cells mimicking neuronal-like cells. After 3 h of incubation, the culture medium in the basal compartment was monitored for 13C enrichment by using elemental analysis isotope-ratio mass spectrometry (EA-IRMS) and effects on cell viability, plasma, and mitochondrial membrane potential. The neurotransmitter activation (BDNF, GABA, choline, and glutamate) of SH-SY5YATRA cells was also determined. Furthermore, these effects were also measured by the direct application of 13C-2´-FL and 13C-Fuc to SH-SY5YATRA cells.

Results

While no effects on neuronal-like cell activities were observed after intact 2´-FL or Fuc was incubated with SH-SY5YATRA cells, supernatants from the stat-growth phase of 2´-FL, fermented by B. longum ssp. infantis alone and together with B. breve, significantly induced BDNF release from SH-SY5YATRA cells. No such effects were found for 2´-FL, Fuc, or their fermentation products from B. breve. The BDNF release occurred from an enhanced vesicular release, which was confirmed by the use of the Ca2+-channel blocker verapamil. Concomitant with this event, 13C enrichment was also observed in the basal compartment when supernatants from the stat-growth phase of fermentation by B. longum ssp. infantis alone or together with B. breve were used.

Conclusion

The results obtained in this study suggest that microbial products of 2´-FL rather than the oligosaccharide itself may influence neuronal cell activities.

Simulated digestions of free oligosaccharides and mucin-type O-glycans reveal a potential role for Clostridium perfringens

The development of a stable human gut microbiota occurs within the first year of life. Many open questions remain about how microfloral species are influenced by the composition of milk, in particular its content of human milk oligosaccharides (HMOs). The objective is to investigate the effect of the human HMO glycome on bacterial symbiosis and competition, based on the glycoside hydrolase (GH) enzyme activities known to be present in microbial species. We extracted from UniProt a list of all bacterial species catalysing glycoside hydrolase activities (EC 3.2.1.-), cross-referencing with the BRENDA database, and obtained a set of taxonomic lineages and CAZy family data. A set of 13 documented enzyme activities was selected and modelled within an enzyme simulator according to a method described previously in the context of biosynthesis. A diverse population of experimentally observed HMOs was fed to the simulator, and the enzymes matching specific bacterial species were recorded, based on their appearance of individual enzymes in the UniProt dataset. Pairs of bacterial species were identified that possessed complementary enzyme profiles enabling the digestion of the HMO glycome, from which potential symbioses could be inferred. Conversely, bacterial species having similar GH enzyme profiles were considered likely to be in competition for the same set of dietary HMOs within the gut of the newborn. We generated a set of putative biodegradative networks from the simulator output, which provides a visualisation of the ability of organisms to digest HMO and mucin-type O-glycans. B. bifidum, B. longum and C. perfringens species were predicted to have the most diverse GH activity and therefore to excel in their ability to digest these substrates. The expected cooperative role of Bifidobacteriales contrasts with the surprising capacities of the pathogen. These findings indicate that potential pathogens may associate in human gut based on their shared glycoside hydrolase digestive apparatus, and which, in the event of colonisation, might result in dysbiosis. The methods described can readily be adapted to other enzyme categories and species as well as being easily fine-tuneable if new degrading enzymes are identified and require inclusion in the model.

Human milk oligosaccharides and the association with microbiota in colostrum: a pilot study

HMOs (Human milk oligosaccharide) has an impact on maternal and infant health. Colostrum samples of 70 breastfeeding women in China were collected and recorded clinical characteristics. The major oligosaccharides and microbiota were quantitated in colostrum. The concentration of fucosylated HMOs in primipara was higher than that of multipara (p = 0.030). The concentration of N-acetylated HMOs in vaginal delivery milk was less than that of cesarean (p = 0.038). Non-fucosylated HMOs of breastfeeding women were less than that of breast pump (p = 0.038). Meanwhile, the concentration of LNT was positively correlated with Lactobacillus (r = 0.250, p = 0.037). DS-LNT was negatively correlated with Staphylococcus (r = - 0.240, p = 0.045). There was a positive correlation of Streptococcus with LNFP II (r = 0.314, p = 0.011) and 3-SL (r = 0.322, p = 0.009). In addition, there was a negative correlation between 2'-FL and 3-FL (r = - 0.465, p = 0.001). There was a positive correlation between LNT and LNnT (r = 0.778, p = 0.001). Therefore, the concentration of HMOs is related to number of deliveries, delivery mode, lactation mode and perinatal antibiotic. The concentration of HMOs is related to Lactobacillus, Streptococcus and Streptococcus in colostrum. In addition, there are connections between different oligosaccharides in content. The study protocol was also registered in the ClinicalTrails.gov (ChiCTR2200064454) (Oct. 2022).

Resource sharing of an infant gut microbiota synthetic community in combinations of human milk oligosaccharides

Quickly after birth, the gut microbiota is shaped via species acquisition and resource pressure. Breastmilk, and more specifically, human milk oligosaccharides are a determining factor in the formation of microbial communities and the interactions between bacteria. Prominent human milk oligosaccharide degraders have been rigorously characterized, but it is not known how the gut microbiota is shaped as a complex community. Here, we designed BIG-Syc, a synthetic community of 13 strains from the gut of vaginally born, breastfed infants. BIG-Syc replicated key compositional, metabolic, and proteomic characteristics of the gut microbiota of infants. Upon fermentation of a four and five human milk oligosaccharide mix, BIG-Syc demonstrated different compositional and proteomic profiles, with Bifidobacterium infantis and Bifidobacterium bifidum suppressing one another. The mix of five human milk oligosaccharides resulted in a more diverse composition with dominance of B. bifidum, whereas that with four human milk oligosaccharides supported the dominance of B. infantis, in four of six replicates. Reintroduction of bifidobacteria to BIG-Syc led to their engraftment and establishment of their niche. Based on proteomics and genome-scale metabolic models, we reconstructed the carbon source utilization and metabolite and gas production per strain. BIG-Syc demonstrated teamwork as cross-feeders utilized simpler carbohydrates, organic acids, and gases released from human milk oligosaccharide degraders. Collectively, our results showed that human milk oligosaccharides prompt resource-sharing for their complete degradation while leading to a different compositional and functional profile in the community. At the same time, BIG-Syc proved to be an accurate model for the representation of intra-microbe interactions.

Label-Free quantitation of milk oligosaccharides from different mammal species and heat treatment influence

Milk oligosaccharides (MOs) exhibit significant variations in concentrations and patterns among different species. However, there is limited knowledge about milk oligosaccharides in domestic animals and the impact of heat treatment on them. Here, we developed an LC-ESI-MS/MS method to analyze 11 milk oligosaccharides in 7 distinct species simultaneously. The results showed that human milk presented a completely different composition pattern of milk oligosaccharides from animals. In detail, animal milk predominantly contained sialylated oligosaccharides, and human milk had high levels of fucosylated neutral oligosaccharides. Notably, sheep milk exhibited similarities to human milk in terms of oligosaccharides composition. Then, the milk samples from dairy cows were treated with two common industrial heat treatments. We found that 65 °C treatment had no significant effect on the concentration of milk oligosaccharides, whereas 135 °C heating was associated with their decline, suggesting that high temperatures should be avoided in the processing of oligosaccharides supplemented/enriched products.

Gastrointestinal barrier function, immunity, and neurocognition: The role of human milk oligosaccharide (hMO) supplementation in infant formula

Breastmilk is seen as the gold standard for infant nutrition as it provides nutrients and compounds that stimulate gut barrier, immune, and brain development to the infant. However, there are many instances where it is not possible for an infant to be fed with breastmilk, especially for the full 6 months recommended by the World Health Organization. In such instances, infant formula is seen as the next best approach. However, infant formulas do not contain human milk oligosaccharides (hMOs), which are uniquely present in human milk as the third most abundant solid component. hMOs have been linked to many health benefits, such as the development of the gut microbiome, the immune system, the intestinal barrier, and a healthy brain. This paper reviews the effects of specific hMOs applied in infant formula on the intestinal barrier, including the not-often-recognized intestinal alkaline phosphatase system that prevents inflammation. Additionally, impact on immunity and the current proof for effects in neurocognitive function and the corresponding mechanisms are discussed. Recent studies suggest that hMOs can alter gut microbiota, modulate intestinal immune barrier function, and promote neurocognitive function. The hMOs 2'-fucosyllactose and lacto-N-neotetraose have been found to have positive effects on the development of infants and have been deemed safe for use in formula. However, their use has been limited due to their cost and complexity of synthesis. Thus, although many benefits have been described, complex hMOs and combinations of hMOs with other oligosaccharides are the best approach to stimulate gut barrier, immune, and brain development and for the prevention of disease.

Human milk oligosaccharides combine with Bifidobacterium longum to form the "golden shield" of the infant intestine: metabolic strategies, health effects, and mechanisms of action

Human milk oligosaccharides (HMOs) are the third most important nutrient in human milk and are the gold standard for infant nutrition. Due to the lack of an enzyme system capable of utilizing HMOs in the infant intestine, HMOs cannot be directly utilized. Instead, they function as natural prebiotics, participating in the establishment of the intestinal microbiota as a "bifidus factor." A crucial colonizer of the early intestine is Bifidobacterium longum (B. longum), particularly its subspecies B. longum subsp. infantis, which is the most active consumer of HMOs. However, due to the structural diversity of HMOs and the specificity of B. longum strains, studies on their synergy are limited. An in-depth investigation into the mechanisms of HMO utilization by B. longum is essential for applying both as synbiotics to promote early intestinal development in infants. This review describes the colonization advantages of B. longum in the infant intestinal tract and its metabolic strategies for HMOs. It also summarizes recent studies on the effect and mechanism of B. longum and HMOs in infant intestinal development directly or indirectly through the action of metabolites. In conclusion, further structural analysis of HMOs and a deeper understanding of the interactions between B. longum and HMOs, as well as clinical trials, are necessary to lay the foundation for future practical applications as synbiotics.

Butyrate interacts with the effects of 2'FL and 3FL to modulate in vitro ovalbumin-induced immune activation, and 2'FL lowers mucosal mast cell activation in a preclinical model for hen's egg allergy

Background

Early life provides a window of opportunity to prevent allergic diseases. With a prevalence of 0.5-2% in infants, hen's egg allergy is one of the most common food allergies. The immunomodulatory effects of human milk oligosaccharides (HMOs), 2'-fucosyllactose (2'FL), and 3-fucosyllactose (3FL) were studied in an in vitro mucosal immune model and an in vivo murine model for hen's egg (ovalbumin) allergy.

Methods

Intestinal epithelial cell (IEC)/dendritic cell (DC) and DC/T cell cocultures were used to expose IECs to ovalbumin (OVA) in an in vitro mucosal immune model. The effects of epithelial pre-incubation with 0.1% 2'FL or 3FL and/or 0.5 mM butyrate were studied. Three- to four-weeks-old female C3H/HeOuJ mice were fed AIN93G diets containing 0.1-0.5% 2'FL or 3FL 2 weeks before and during OVA sensitization and challenge. Allergic symptoms and systemic and local immune parameters were assessed.

Results

Exposing IECs to butyrate in vitro left the IEC/DC/T cell cross-talk unaffected, while 2'FL and 3FL showed differential immunomodulatory effects. In 3FL exposed IEC-DC-T cells, the secretion of IFNγ and IL10 was enhanced. This was observed upon pre-incubation of IECs with 2'FL and butyrate as well, but not 2'FL alone. The presence of butyrate did not affect OVA activation, but when combined with 3FL, an increase in IL6 release from DCs was observed (p < 0.001). OVA allergic mice receiving 0.5% 3FL diet had a lower %Th2 cells in MLNs, but the humoral response was unaltered compared to control mice. OVA-allergic mice receiving 0.1 or 0.5% 2'FL diets had lower serum levels of OVA-IgG2a (p < 0.05) or the mast cell marker mMCP1, in association with increased concentration of cecal short-chain fatty acids (SCFAs) (p < 0.05).

Conclusion

In vitro butyrate exposure promotes the development of a downstream type 1 and regulatory response observed after 2'FL exposure. 2'FL and 3FL differentially modulate ovalbumin-induced mucosal inflammation predominantly independent of butyrate. Mice receiving dietary 3FL during ovalbumin sensitization and challenge had lowered Th2 activation while the frequency of Treg cells was enhanced. By contrast, 2'FL improved the humoral immune response and suppressed mast cell activation in association with increased SCFAs production in the murine model for hen's egg allergy.

An Overview of the Influence of Breastfeeding on the Development of Inflammatory Bowel Disease

The first 1000 days of life is a critical period that contributes significantly to the programming of an individual's future health. Among the many changes that occur during this period early in life, there is growing evidence that the establishment of healthy gut microbiota plays an important role in the prevention of both short- and long-term health problems. Numerous publications suggest that the quality of the gut microbiota colonisation depends on several dietary factors, including breastfeeding. In this respect, a relationship between breastfeeding and the risk of inflammatory bowel disease (IBD) has been suggested. IBDs are chronic intestinal diseases, and perinatal factors may be partly responsible for their onset. We review the existence of links between breastfeeding and IBD based on experimental and clinical studies. Overall, despite encouraging experimental data in rodents, the association between breastfeeding and the development of IBD remains controversial in humans, partly due to the considerable heterogeneity between clinical studies. The duration of exclusive breastfeeding is probably decisive for its lasting effect on IBD. Thus, specific improvements in our knowledge could support dietary interventions targeting the gut microbiome, such as the early use of prebiotics, probiotics or postbiotics, in order to prevent the disease.

Safety of lacto-N-fucopentaose I/2'-fucosyllactose (LNFP-I/2'-FL) mixture as a novel food pursuant to Regulation (EU) 2015/2283

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on lacto-N-fucopentaose I (LNFP-I)/2'-fucosyllactose (2'-FL) mixture as a novel food (NF) pursuant to Regulation (EU) 2015/2283. The NF is mainly composed of the human-identical milk oligosaccharides (HiMO) LNFP-I and 2'-FL, but it also contains d-lactose, lacto-N-tetraose, difucosyllactose, 3-fucosyllactose, LNFP-I fructose isomer, 2'-fucosyl-d-lactulose, l-fucose and 2'-fucosyl-d-lactitol, and a small fraction of other related saccharides. The NF is produced by fermentation by a genetically modified strain (Escherichia coli K-12 DH1 MDO MP2173b) of E. coli K-12 DH1 (DSM 4235). The information provided on the identity, manufacturing process, composition and specifications of the NF does not raise safety concerns. The applicant intends to add the NF in a variety of foods, including infant formula (IF) and follow-on formula, foods for infants and toddlers, foods for special medical purposes and food supplements (FS). The target population is the general population. The anticipated daily intake of LNFP-I from use in IF is similar to the estimated natural mean highest daily intake in breastfed infants. Overall, the anticipated daily intake of LNFP-I from the NF as a food ingredient at the maximum proposed use levels is unlikely to exceed the intake level of breastfed infants on a body weight basis. The intake in breastfed infants on a body weight basis is expected to be safe also for other population groups. The anticipated 2'-FL intake is generally rather low. The use of the NF in FS is not intended if other foods with added NF components or human milk (for infants and young children) are consumed on the same day. The Panel concludes that the NF, a mixture of LNFP-I and 2'-FL, is safe under the proposed conditions of use.