Selective Utilization of the Human Milk Oligosaccharides 2'-Fucosyllactose, 3-Fucosyllactose, and Difucosyllactose by Various Probiotic and Pathogenic Bacteria

Surface Proteins of Bifidobacterium Bifidum DNG6 Growing in 2'-FL Alleviating LPS-Induced Intestinal Barrier Injury in vitro

Human milk oligosaccharides (HMOs) promote the growth and adhesion of bifidobacteria, thus exerting multiple biological functions on intestinal epithelial cells. Bacterial surface proteins play an important role in bacterial-host intestinal epithelial interactions. In this study, we aim to investigate the effects of surface proteins extracted from Bifidobacterium bifidum DNG6 (B. bifidum DNG6) consuming 2'-fucosyllactose (2'-FL) on Caco-2 cells monolayer barrier injury induced by lipopolysaccharide, compared with lactose (Lac) and galacto-oligosaccharides (GOS). Our results indicated that 2'-FL may promote the surface proteins of B. bifidum DNG6 to improve intestinal barrier injury by positively regulating the NF-κB signaling pathway, reducing inflammation(TNF-α reduced to 50.34%, IL-6 reduced to 22.83%, IL-1β reduced to 37.91%, and IL-10 increased to 63.47%)and strengthening tight junction (ZO-1 2.39 times, Claudin-1 2.79 times, and Occludin 4.70 times). The findings of this study indicate that 2'-FL can further regulate intestinal barrier damage by promoting the alteration of B. bifidum DNG6 surface protein. The findings of this research will also provide theoretical support for the development of synbiotic formulations.

Combinatorial Optimization Strategies for 3-Fucosyllactose Hyperproduction in Escherichia coli

3-Fucosyllactose (3-FL), an important fucosylated human milk oligosaccharide in breast milk, offers numerous health benefits to infants. Previously, we metabolically engineered Escherichia coli BL21(DE3) for the in vivo biosynthesis of 3-FL. In this study, we initially optimized culture conditions to double 3-FL production. Competing pathway genes involved in in vivo guanosine 5'-diphosphate-fucose biosynthesis were subsequently inactivated to redirect fluxes toward 3-FL biosynthesis. Next, three promising transporters were evaluated using plasmid-based or chromosomally integrated expression to maximize extracellular 3-FL production. Additionally, through analysis of α1,3-fucosyltransferase (FutM2) structure, we identified Q126 residues as a highly mutable residue in the active site. After site-saturation mutation, the best-performing mutant, FutM2-Q126A, was obtained. Structural analysis and molecular dynamics simulations revealed that small residue replacement positively influenced helical structure generation. Finally, the best strain BD3-A produced 6.91 and 52.1 g/L of 3-FL in a shake-flask and fed-batch cultivations, respectively, highlighting its potential for large-scale industrial applications.

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.

Personalized Nutrition with Banked Human Milk for Early Gut Microbiota Development: In Pursuit of the Perfect Match

The correct initial colonization and establishment of the gut microbiota during the early stages of life is a key step, with long-lasting consequences throughout the entire lifespan of the individual. This process is affected by several perinatal factors; among them, feeding mode is known to have a critical role. Breastfeeding is the optimal nutrition for neonates; however, it is not always possible, especially in cases of prematurity or early pathology. In such cases, most commonly babies are fed with infant formulas in spite of the official nutritional and health international organizations' recommendation on the use of donated human milk through milk banks for these cases. However, donated human milk still does not totally match maternal milk in terms of infant growth and gut microbiota development. The present review summarizes the practices of milk banks and hospitals regarding donated human milk, its safety and quality, and the health outcomes in infants fed with donated human milk. Additionally, we explore different alternatives to customize pasteurized donated human milk with the aim of finding the perfect match between each baby and banked milk for promoting the establishment of a beneficial gut microbiota from the early stages of life.

Human milk oligosaccharide composition is affected by season and parity and associates with infant gut microbiota in a birth mode dependent manner in a Finnish birth cohort

BACKGROUND

Human milk oligosaccharides (HMOs), their determinants, infant gut microbiota and health are under extensive research; however, seldom jointly addressed. Leveraging data from the HELMi birth cohort, we investigated them collectively, considering maternal and infant secretor status.

METHODS

HMO composition in breastmilk collected 3 months postpartum (n = 350 mothers) was profiled using high-performance liquid chromatography. Infant gut microbiota taxonomic and functional development was studied at 3, 6, and 12 months (n = 823 stool samples) via shotgun metagenomic sequencing, focusing on HMO metabolism via glycoside hydrolase (GH) analysis. Maternal and infant secretor statuses were identified through phenotyping and genotyping, respectively. Child health, emphasizing allergies and antibiotics as proxies for infectious diseases, was recorded until 2 years.

FINDINGS

Mother's parity, irritable bowel syndrome, gestational diabetes, and season of milk collection associated with HMO composition. Neither maternal nor infant secretor status associated with infant gut microbiota, except for a few taxa linked to individual HMOs. Analysis stratified for birth mode revealed distinct patterns between the infant gut microbiota and HMOs. Child health parameters were not associated to infant or maternal secretor status.

INTERPRETATION

This comprehensive exploration unveils intricate links between secretor genotype, maternal factors, HMO composition, infant microbiota, and child health. Understanding these nuanced relationships is paramount for refining strategies to optimize early life nutrition and its enduring impact on long-term health.

FUNDING

Sweet Crosstalk EU H2020 MSCA ITN, Academy of Finland, Mary and Georg C. Ehrnrooth Foundation, Päivikki and Sakari Sohlberg Foundation, and Tekes.

Unlocking the mysteries of milk oligosaccharides: Structure, metabolism, and function

Milk oligosaccharides (MOs), complex carbohydrates prevalent in human breast milk, play a vital role in infant nutrition. Serving as prebiotics, they inhibit pathogen adherence, modulate the immune system, and support newborn brain development. Notably, MOs demonstrate significant variations in concentration and composition, both across different species and within the same species. These characteristics of MOs lead to several compelling questions: (i) What distinct beneficial functions do MOs offer and how do the functions vary along with their structural differences? (ii) In what ways do MOs in human milk differ from those in other mammals, and what factors drive these unique profiles? (iii) What are the emerging applications of MOs, particularly in the context of their incorporation into infant formula? This review delves into the structural characteristics, quantification methods, and species-specific concentration differences of MOs. It highlights the critical role of human MOs in infant growth and their potential applications, providing substantial evidence to enhance infant health and development.

Human milk oligosaccharide 2'-fucosyllactose protects against high-fat diet-induced obesity by changing intestinal mucus production, composition and degradation linked to changes in gut microbiota and faecal proteome profiles in mice

OBJECTIVE

To decipher the mechanisms by which the major human milk oligosaccharide (HMO), 2'-fucosyllactose (2'FL), can affect body weight and fat mass gain on high-fat diet (HFD) feeding in mice. We wanted to elucidate whether 2'FL metabolic effects are linked with changes in intestinal mucus production and secretion, mucin glycosylation and degradation, as well as with the modulation of the gut microbiota, faecal proteome and endocannabinoid (eCB) system.

RESULTS

2'FL supplementation reduced HFD-induced obesity and glucose intolerance. These effects were accompanied by several changes in the intestinal mucus layer, including mucus production and composition, and gene expression of secreted and transmembrane mucins, glycosyltransferases and genes involved in mucus secretion. In addition, 2'FL increased bacterial glycosyl hydrolases involved in mucin glycan degradation. These changes were linked to a significant increase and predominance of bacterial genera Akkermansia and Bacteroides, different faecal proteome profile (with an upregulation of proteins involved in carbon, amino acids and fat metabolism and a downregulation of proteins involved in protein digestion and absorption) and, finally, to changes in the eCB system. We also investigated faecal proteomes from lean and obese humans and found similar changes observed comparing lean and obese mice.

CONCLUSION

Our results show that the HMO 2'FL influences host metabolism by modulating the mucus layer, gut microbiota and eCB system and propose the mucus layer as a new potential target for the prevention of obesity and related disorders.

Genome plasticity shapes the ecology and evolution of Phocaeicola dorei and Phocaeicola vulgatus

Phocaeicola dorei and Phocaeicola vulgatus are very common and abundant members of the human gut microbiome and play an important role in the infant gut microbiome. These species are closely related and often confused for one another; yet, their genome comparison, interspecific diversity, and evolutionary relationships have not been studied in detail so far. Here, we perform phylogenetic analysis and comparative genomic analyses of these two Phocaeicola species. We report that P. dorei has a larger genome yet a smaller pan-genome than P. vulgatus. We found that this is likely because P. vulgatus is more plastic than P. dorei, with a larger repertoire of genetic mobile elements and fewer anti-phage defense systems. We also found that P. dorei directly descends from a clade of P. vulgatus¸ and experienced genome expansion through genetic drift and horizontal gene transfer. Overall, P. dorei and P. vulgatus have very different functional and carbohydrate utilisation profiles, hinting at different ecological strategies, yet they present similar antimicrobial resistance profiles.

A 21-day safety evaluation of biotechnologically produced 3-fucosyllactose (3-FL) in neonatal farm piglets to support use in infant formulas

3-Fucosyllactose (3-FL) is one of the most abundant fucosylated oligosaccharides in human breast milk and is an approved infant formula ingredient world-wide. 3-FL functions as a prebiotic to promote early microbial colonization of the gut, increase pathogen resistance and modulate immune responses. To investigate safety and potential gut microbiota effects, 3-FL was fed for 21-days to farm piglets beginning on Postnatal Day (PND) 2. Fructooligosaccharide (FOS), an approved infant formula ingredient, was used as a reference control. Standard toxicological endpoints were evaluated, and the gut microbiota were assessed. Neither 3-FL (245.77 and 489.72 mg/kg/day for males and 246.57 and 494.18 mg/kg/day for females) nor FOS (489.44 and 496.33 mg/kg/day males and females, respectively) produced any adverse differences in growth, food intake or efficiency, clinical observations, or clinical or anatomic pathology changes. Differences in the gut microbiota after 3-FL consumption (versus control and FOS groups) included the absence of Bifidobacterium species from the piglets, enrichment of Prevotellamassilia timonensis, Blautia species, Mediterranea massiliensis, Lachnospiraceae incertae sedis, and Eubacterium coprostanoligens and lower relative abundance of Allisonella histaminiformans and Roseburia inulinivorans. This study further supports the safe use of 3-FL produced using biotechnology as a nutritional ingredient in foods.

Molecular docking studies on α-amylase inhibitory peptides from milk of different farm animals

Milk-derived peptides have emerged as a popular mean to manage various lifestyle disorders such as diabetes. Fermentation is being explored as one of the faster and efficient way of producing peptides with antidiabetic potential. Therefore, in this study, an attempt was made to comparatively investigate the pancreatic α-amylase (PAA) inhibitory properties of peptides derived from milk of different farm animals through probiotic fermentation. Peptide's identification was carried out using liquid chromatography-quadrupole time-of-flight mass spectrometry and inhibition mechanisms were characterized by molecular docking. Results obtained showed a PAA-IC50 value (the amount of protein equivalent needed to inhibit 50% of enzymes) between 2.39 and 36.1 µg protein equivalent for different fermented samples. Overall, Pediococcus pentosaceus MF000957-derived fermented milk from all animals indicated higher PAA inhibition than other probiotic derived fermented milk (PAA-IC50 values of 6.01, 3.53, 15.6, and 10.8 µg protein equivalent for bovine, camel, goat, and sheep fermented milk). Further, molecular docking analysis indicated that camel milk-derived peptide IMEQQQTEDEQQDK and goat milk-derived peptide DQHQKAMKPWTQPK were the most potent PAA inhibitory peptides. Overall, the study concluded that fermentation derived peptides may prove useful in for managing diabetes via inhibition of carbohydrate digesting enzyme PAA.

Next generation probiotics: Engineering live biotherapeutics

The population dynamics of the human microbiome have been associated with inflammatory bowel disease, cancer, obesity, autoimmune diseases, and many other human disease states. An emerging paradigm in treatment is the administration of live engineered organisms, also called next-generation probiotics. However, the efficacy of these microbial therapies can be limited by the organism's overall performance in the harsh and nutrient-limited environment of the gut. In this review, we summarize the current state of the art use of bacterial and yeast strains as probiotics, highlight the recent development of genetic tools for engineering new therapeutic functions in these organisms, and report on the latest therapeutic applications of engineered probiotics, including recent clinical trials. We also discuss the supplementation of prebiotics as a method of manipulating the microbiome and improving the overall performance of engineered live biotherapeutics.

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.

Linking human milk oligosaccharide metabolism and early life gut microbiota: bifidobacteria and beyond

SUMMARYHuman milk oligosaccharides (HMOs) are complex, multi-functional glycans present in human breast milk. They represent an intricate mix of heterogeneous structures which reach the infant intestine in an intact form as they resist gastrointestinal digestion. Therefore, they confer a multitude of benefits, directly and/or indirectly, to the developing neonate. Certain bifidobacterial species, being among the earliest gut colonizers of breast-fed infants, have an adapted functional capacity to metabolize various HMO structures. This ability is typically observed in infant-associated bifidobacteria, as opposed to bifidobacteria associated with a mature microbiota. In recent years, information has been gleaned regarding how these infant-associated bifidobacteria as well as certain other taxa are able to assimilate HMOs, including the mechanistic strategies enabling their acquisition and consumption. Additionally, complex metabolic interactions occur between microbes facilitated by HMOs, including the utilization of breakdown products released from HMO degradation. Interest in HMO-mediated changes in microbial composition and function has been the focal point of numerous studies, in recent times fueled by the availability of individual biosynthetic HMOs, some of which are now commonly included in infant formula. In this review, we outline the main HMO assimilatory and catabolic strategies employed by infant-associated bifidobacteria, discuss other taxa that exhibit breast milk glycan degradation capacity, and cover HMO-supported cross-feeding interactions and related metabolites that have been described thus far.

2'-Fucosyllactose Promotes Colonization of Akkermansia muciniphila and Prevents Colitis In Vitro and in Mice

Akkermansia muciniphila is a potential candidate for ulcerative colitis prevention. Considering that it utilizes 2'-fucosyllactose (2'FL) for growth, 2'FL can be used to enrich the abundance of A. muciniphila in feces. However, whether the crosswalk between 2'FL and A. muciniphila can promote the intestinal colonization of A. muciniphila remains unclear. In this study, we explored the effect and the underlying mechanism of 2'FL on the colonization of A. muciniphila in vitro and in vivo as well as its alleviating effect on colitis. Our results revealed that 2'FL can serve as a carbon source of A. muciniphila to support the growth and increase cell-surface hydrophobicity and the expression of the genes coding fibronectin-binding autotransporter adhesin to promote the adhesion to Caco2/HT29 methotrexate (MTX) cells but not of galactooligosaccharides (GOS) and glucose. Moreover, 2'FL could increase the host mucin formation to promote the adhesion of A. muciniphila to Caco2/HT29 MTX cells but not of GOS and glucose. Furthermore, 2'FL could significantly increase the colonization of A. muciniphila in the gut to alleviate colitis in mice. Overall, the interplay between A. muciniphila and 2'FL is expected to provide an advantageous ecological niche for A. muciniphila so as to confer further health benefits against colitis.

Bifidobacterium longum modifies a nutritional intervention for stunting in Zimbabwean infants

Child stunting is an indicator of chronic undernutrition and reduced human capital. However, it remains a poorly understood public health problem. Small-quantity lipid-based nutrient supplements (SQ-LNS) have been widely tested to reduce stunting, but have modest effects. The infant intestinal microbiome may contribute to stunting, and is partly shaped by mother and infant histo-blood group antigens (HBGA). We investigated whether mother-infant fucosyltransferase status, which governs HBGA, and the infant gut microbiome modified the impact of SQ-LNS on stunting at age 18 months among Zimbabwean infants in the SHINE Trial ( NCT01824940 ). We found that mother-infant fucosyltransferase discordance and Bifidobacterium longum reduced SQ-LNS efficacy. Infant age-related microbiome shifts in B. longum subspecies dominance from infantis , a proficient human milk oligosaccharide utilizer, to suis or longum , proficient plant-polysaccharide utilizers, were partly influenced by discordance in mother-infant FUT2+/FUT3- phenotype, suggesting that a "younger" microbiome at initiation of SQ-LNS reduces its benefits on stunting.

Consistency and Variability of the Human Milk Oligosaccharide Profile in Repeat Pregnancies

Human milk oligosaccharides (HMOs) are a set of complex carbohydrates and the third largest solid component of human milk, after lactose and lipids. To date, over 150 HMOs have been identified and the diversity of structures produced by lactating women is influenced by maternal genetics as well as other maternal, infant, and environmental factors. While the concentrations of individual HMOs have been shown to vary between individuals and throughout the course of lactation, the variability of HMO concentration profiles following different pregnancies occurring in the same woman is presently unknown. As such, the objective of this study was to compare HMO concentrations in human milk samples provided by the same women (n = 34) following repeat pregnancies. We leveraged existing human milk samples and metadata from the UC San Diego Human Milk Research Biorepository (HMB) and measured the concentrations of the 19 most abundant HMOs using high-performance liquid chromatography with fluorescence detection (HPLC-FL). By assessing dissimilarities in HMO concentration profiles, as well as concentration trends in individual structures between pregnancies of each participant, we discovered that HMO profiles largely follow a highly personalized and predictable trajectory following different pregnancies irrespective of non-genetic influences. In conclusion, this is the first study to assess the interactions between parity and time following delivery on variations in HMO compositions.

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.

Fermentation characteristics and prebiotic potential of enzymatically synthesized butyryl-fructooligosaccharides

Existing prebiotics, such as fructo-oligosaccharides (FOSs), can be modified to enhance their functionality or introduce additional functionalities. This study aimed to investigate the fermentation characteristics and prebiotic potential of enzymatically synthesized butyryl-FOSs. The esters were successfully synthesized through the reaction of butyric acid and FOSs using both chemical and enzymatic methods, denoted as A-FOSs and B-FOSs, respectively, for comparative analysis. The esterification degree of each component in A-FOSs was significantly higher than that of B-FOSs. Subsequently, the obtained esters were characterized for their fermentation properties, degradation mode and potential prebiotic effects using an in vitro simulated colonic fermentation model. Enzymes of human gut microbiota were found to preferentially cleave the glycosidic bond to the unit without butyryl group and release the sugars for utilization. A significant increase in butyric acid levels was observed during fermentation after the supplementation of B-FOSs. The 16S rRNA gene sequencing, absolute quantification of microbiota, and selected probiotic strains culture showed that B-FOSs supplementation promoted the growth of beneficial bacteria while reducing harmful ones. These results suggest that B-FOSs hold promise as novel prebiotics, possessing dual functions of modulating gut microbiota and delivering butyric acid to the colon in a targeted manner, ultimately contributing to improved gut health.

CRISPR-Cas-based identification of a sialylated human milk oligosaccharides utilization cluster in the infant gut commensal Bacteroides dorei

The infant gut microbiome is impacted by early-life feeding, as human milk oligosaccharides (HMOs) found in breastmilk cannot be digested by infants and serve as nutrients for their gut bacteria. While the vast majority of HMO-utilization research has focused on Bifidobacterium species, recent studies have suggested additional HMO-utilizers, mostly Bacteroides, yet their utilization mechanism is poorly characterized. Here, we investigate Bacteroides dorei isolates from breastfed-infants and identify that polysaccharide utilization locus (PUL) 33 enables B. dorei to utilize sialylated HMOs. We perform transcriptional profiling and identity upregulated genes when growing on sialylated HMOs. Using CRISPR-Cas12 to knock-out four PUL33 genes, combined with complementation assays, we identify GH33 as the critical gene in PUL33 for sialylated HMO-utilization. This demonstration of an HMO-utilization system by Bacteroides species isolated from infants opens the way to further characterization of additional such systems, to better understand HMO-utilization in the infant gut.

Molecular strategies for the utilisation of human milk oligosaccharides by infant gut-associated bacteria

A number of bacterial species are found in high abundance in the faeces of healthy breast-fed infants, an occurrence that is understood to be, at least in part, due to the ability of these bacteria to metabolize human milk oligosaccharides (HMOs). HMOs are the third most abundant component of human milk after lactose and lipids, and represent complex sugars which possess unique structural diversity and are resistant to infant gastrointestinal digestion. Thus, these sugars reach the infant distal intestine intact, thereby serving as a fermentable substrate for specific intestinal microbes, including Firmicutes, Proteobacteria, and especially infant-associated Bifidobacterium spp. which help to shape the infant gut microbiome. Bacteria utilising HMOs are equipped with genes associated with their degradation and a number of carbohydrate-active enzymes known as glycoside hydrolase enzymes have been identified in the infant gut, which supports this hypothesis. The resulting degraded HMOs can also be used as growth substrates for other infant gut bacteria present in a microbe-microbe interaction known as 'cross-feeding'. This review describes the current knowledge on HMO metabolism by particular infant gut-associated bacteria, many of which are currently used as commercial probiotics, including the distinct strategies employed by individual species for HMO utilisation.

2'-Fucosyllactose (2'-FL) changes infants gut microbiota composition and their metabolism in a host-free human colonic model

BACKGROUND

Breast milk is critical for neonates, providing the necessary energy, nutrients, and bioactive compounds for growth and development. Research indicated that human milk oligosaccharides (HMOs) have been shown to shape a beneficial gut microbiota, as well as their metabolism (e.g. short-chain fatty acids). 2'-Fucosyllactose (2'-FL) is one major HMO that composed of 30% of total HMOs.

OBJECTIVES

This study aimed to understand the impact of 2'-FL on the composition and metabolism of infant gut microbiota.

METHODS

Our study utilized an in-vitro human colonic model (HCM) to investigate the host-free interactions between 2'-FL and infant gut microbiota. To simulate the infant gut microbiota, we inoculated the HCM system with eight representative bacterial species from infant gut microbiota. The effects of 2'-FL on the gut microbial composition and their metabolism were determined through real-time quantitative PCR and liquid-chromatography mass spectrometry (LC/MS). The obtained data were analyzed using Compound Discoverer 3.1 and MetaboAnalyst 4.0.

RESULTS

Our study findings suggest that the intervention of 2'-FL in HCM resulted in a significant change in the abundance of representative bacterial species. PCR analysis showed a consistent increase in the abundance of Parabacteroides. distasonis in all three colon sections. Furthermore, analysis of free fatty acids revealed a significant increase in their levels in the ascending, transverse, and descending colons, except for caproic acid, which was significantly reduced to a non-detectable level. The identification of significant extracellular polar metabolites, such as glutathione and serotonin, enabled us to distinguish between the metabolomes before and after 2'-FL intervention. Moreover, correlation analysis revealed a significant association between the altered microbes and microbial metabolites.

CONCLUSIONS

In summary, our study demonstrated the impact of 2'-FL intervention on the defined composition of infant gut microbiota and their metabolic pathways in an in vitro setting. Our findings provide valuable insights for future follow-up investigations into the role of 2'-FL in regulating the growth and development of infant gut microbiota in vivo.

Supplementing maternal diet with milk oligosaccharides and probiotics helps develop the immune system and intestinal flora of offsprings

Intestinal flora is very important for improving the development of the immune system in newborns. Maternal diet during pregnancy and lactation is one of the key factors affecting the growth and development of offspring. The objective of the present study was to examine whether supplementation of maternal diet with milk oligosaccharides and Bifidobacterium could influence the development of the intestinal flora and immune system of neonatal mice. In total, 30 pregnant Institute of Cancer Research (ICR) mice were randomly divided into six groups: a control group (basal diet) and five intervention groups (basal diet supplemented with different doses of 2'-fucosyllactose [2'-FL] and Bifidobacterium Bb12) during the pregnancy period. All female mice were monitored for physical health during gavage. After delivery, the number of mice in each litter, any deformity, and the development of the offspring were recorded. The spleen, blood, and fecal samples of six groups of 10-12 day-old offspring were collected. The results demonstrated that maternal milk oligosaccharides and probiotics conferred protective effects against lipopolysaccharide (LPS)-induced immunosuppression in mice offspring by significantly enhancing the immune organ indexes, splenocyte proliferation, immunoglobulin (immunoglobulin G, A, M) production as well as improving the macrophage phagocytosis (p < .05). The abundance of Lactobacilli and Bifidobacteria in the feces of offspring mice in the intervention groups was significantly higher than that of the offspring mice in the control group (p < .05). These findings suggest that the combination of 2'-FL and Bifidobacterium Bb12 displayed synergistic interactions between the two components that could promote the development of the immune system of the offsprings and improve their microbiota through maternal ingestion.

Structural and binding studies of 2'- and 3-fucosyllactose and its complexes with norovirus capsid protein by molecular dynamics simulations

Human breast milk contains free oligosaccharides (Human Milk Oligosaccharides-HMOs) that help to protect breastfed infants against a variety of infectious diseases and act as decoy receptors. In breast milk, HMOs are the third most abundant compounds after lactose and lipids. Structural and conformational models of HMOs are quite crucial to studying the interaction with proteins and molecular recognition phenomenon. Molecular dynamics simulations for two trisaccharides HMOs (2'-FL and 3-FL) were carried out for 250 ns and the conformational models were subsequently substantiated by three replicate simulations. The conformer models of HMOs 2'-FL and 3-FL were deposited in the 3-Dimensional Structural Database for Sialic acid-containing CARbohydrates (3DSDSCAR) database website (www.3dsdscar.in). HMOs were then docked into the active site of norovirus capsid protein and are simulated for 100 ns duration. Each complex system was stabilized by direct and water-mediated hydrogen bonding interactions. Binding free energy calculations predict two possible binding modes for each complex system. The conformational flexibility and binding stability of the complex systems were calculated. The protein folding/unfolding and compactness seem to be better for the two HMOs. From a general perspective, we found that both 2'-FL and 3-FL exhibited higher binding efficacy towards norovirus capsid protein and according to the structural stability, 3-FL might be used as a preventive inhibitor for norovirus infection.Communicated by Ramaswamy H. Sarma.

2-Fucosyllactose Metabolism by Bifidobacteria Promotes Lactobacilli Growth in Co-Culture

Breastfeeding is recognized as the gold standard in infant nutrition, not only because of breastmilk's intrinsic nutritional benefits but also due to the high content of different bioactive components such as 2-fucosyllactose (2'FL) in the mother's milk. It promotes the growth of its two major consumers, Bifidobacterium longum ssp. infantis and Bifidobacterium bifidum, but the effect on other intestinal microorganisms of infant microbiota remains incompletely understood. pH-uncontrolled fecal cultures from infants donors identified as "fast 2'FL -degrader" microbiota phenotype were used for the isolation of 2'FL-associated microorganisms. The use of specific selective agents allowed the successful isolation of B. bifidum IPLA20048 and of Lactobacillus gasseri IPLA20136. The characterization of 2'FL consumption and its moieties has revealed more pronounced growth, pH drop, and lactic acid production after 2'FL consumption when both microorganisms were grown together. The results point to an association between B. bifidum IPLA20048 and L. gasseri IPLA20136 in which L. gasseri is able to use the galactose from the lactose moiety after the hydrolysis of 2'FL by B. bifidum. The additional screening of two groups of bifidobacteria (n = 38), fast and slow degraders of 2'FL, in co-culture with lactobacilli confirmed a potential cross-feeding mechanism based on degradation products released from bifidobacterial 2'FL break-down. Our work suggests that this phenomenon may be widespread among lactobacilli and bifidobacteria in the infant gut. More investigation is needed to decipher how the ability to degrade 2'FL and other human milk oligosaccharides could influence the microbiota establishment in neonates and the evolution of the microbiota in adult life.

Review and Perspectives on Bifidobacterium lactis for Infants' and Children's Health

The influence of microbiota dysbiosis in early life is increasingly recognized as a risk factor for the development of several chronic diseases later in life, including an increased risk of asthma, eczema, allergies, obesity, and neurodevelopmental disorders. The question whether the potential lifelong consequences of early life dysbiosis could be mitigated by restoring microbiota composition remains unresolved. However, the current evidence base suggests that protecting the normal development of the microbiome during this critical developmental window could represent a valuable public health strategy to curb the incidence of chronic and lifestyle-related diseases. Probiotic Bifidobacteria are likely candidates for this purpose in newborns and infants considering the natural dominance of this genus on microbiota composition in early life. Moreover, the most frequently reported microbiota composition alteration in association with newborn and infant diseases, including necrotizing enterocolitis and diarrhea, is a reduction in Bifidobacteria levels. Several studies have assessed the effects of B. animalis subsp. lactis strains in newborns and infants, but recent expert opinions recommend analyzing their efficacy at the strain-specific level. Hence, using the B94 strain as an example, this review summarizes the clinical evidence available in infants and children in various indications, discussing the safety and potential modes of actions while providing perspectives on the concept of "non-infant-type" probiotics for infants' health.

Genome-scale metabolic modeling of the human gut bacterium Bacteroides fragilis strain 638R

Bacteroides fragilis is a universal member of the dominant commensal gut phylum Bacteroidetes. Its fermentation products and abundance have been linked to obesity, inflammatory bowel disease, and other disorders through its effects on host metabolic regulation and the immune system. As of yet, there has been no curated systems-level characterization of B. fragilis' metabolism that provides a comprehensive analysis of the link between human diet and B. fragilis' metabolic products. To address this, we developed a genome-scale metabolic model of B. fragilis strain 638R. The model iMN674 contains 1,634 reactions, 1,362 metabolites, three compartments, and reflects the strain's ability to utilize 142 metabolites. Predictions made with this model include its growth rate and efficiency on these substrates, the amounts of each fermentation product it produces under different conditions, and gene essentiality for each biomass component. The model highlights and resolves gaps in knowledge of B. fragilis' carbohydrate metabolism and its corresponding transport proteins. This high quality model provides the basis for rational prediction of B. fragilis' metabolic interactions with its environment and its host.

Enhancing Bioaccessibility of Plant Protein Using Probiotics: An In Vitro Study

As plant-based diets become more popular, there is an interest in developing innovations to improve the bioaccessibility of plant protein. In this study, seven probiotic strains (Bifidobacterium animalis subsp. lactis B420, B. lactis Bl-04, Lactobacillus acidophilus NCFM, Lacticaseibacillus rhamnosus HN001, Lacticaseibacillus paracasei subsp. paracasei Lpc-37, Lactiplantibacillus plantarum Lp-115, and Lactococcus lactis subsp. lactis Ll-23) were evaluated for their capacity to hydrolyze soy and pea protein ingredients in an in vitro digestion model of the upper gastrointestinal tract (UGIT). Compared to the control digestion of protein without a probiotic, all the studied strains were able to increase the digestion of soy or pea protein, as evidenced by an increase in free α-amino nitrogen (FAN) and/or free amino acid concentration. The increase in FAN varied between 13 and 33% depending on the protein substrate and probiotic strain. The survival of probiotic bacteria after exposure to digestive fluids was strain-dependent and may have affected the strain's capacity to function and aid in protein digestion in the gastrointestinal environment. Overall, our results from the standardized in vitro digestion model provide an approach to explore probiotics for improved plant protein digestion and bioaccessibility of amino acids; however, human clinical research is needed to evaluate the efficacy of probiotics on amino acid absorption and bioavailability in vivo.

Human breast milk: A promising treatment for necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a severe gastrointestinal disorder occurring in newborns, with a mortality rate ranging from 20 % to 30 %. The existing therapeutic approaches for NEC are limited in their effectiveness. Various factors contribute to the development of NEC, including disruption of barrier function, dysregulation of the intestinal immune system, and abnormal colonization of the intestinal microbiota. Researchers have shown considerable interest in exploring the therapeutic potential of the constituents present in human breast milk (HBM) for treating NEC. HBM contains numerous bioactive components, such as exosomes, growth factors, and oligosaccharides. However, the precise mechanisms by which HBM exerts its protective effects against NEC remain incompletely understood. In this study, our objective was to comprehensively review the bioactive substances present in HBM, aiming to facilitate the development of novel therapeutic strategies for NEC.

Persistence of maternal milk derived Lactobacillus plantarum in the infant feces and its antagonistic activity against Escherichia coli O157:H7

The diversity of lactic acid bacteria (LAB) in maternal milk and feces from Thai mother-infants pairs were revealed through nested PCR-DGGE. LAB species residing in maternal milk drawn from each individual demonstrated high uniqueness, yet shared similarity to her infant. Multiple strains of L. plantarum, L. fermentum, L. rhamnosus, L. mucosae, L. casei were continuously detected, suggesting direct transfer from a mother to her infant via breastfeeding. L. plantarum, the most commonly found species with many strain variants, remained persistent in infant's feces up to six months postpartum. Such success could be achieved through its ability to utilize fructooligosaccharides (FOS)/inulin together with antibacterial activity and competitive adhesion. With FOS/inulin, the prebiotic utilizing L. plantarum (M117 and M118) isolated from maternal milk effectively inhibited E. coli O157:H7 under highly microflora competitive and glucose-limited environments of colon model. The results introduce the potential trend for development of effective anti-diarrheal synbiotic infant formulae.

Interactions between Bifidobacterium and Bacteroides and human milk oligosaccharides and their associations with infant cognition

While ample research on independent associations between infant cognition and gut microbiota composition and human milk (HM) oligosaccharides (HMOs) has been reported, studies on how the interactions between gut microbiota and HMOs may yield associations with cognitive development in infancy are lacking. We aimed to determine how HMOs and species of Bacteroides and Bifidobacterium genera interact with each other and their associations with cognitive development in typically developing infants. A total of 105 mother-infant dyads were included in this study. The enrolled infants [2.9-12 months old (8.09 ± 2.48)] were at least predominantly breastfed at 4 months old. A total of 170 HM samples from the mothers and fecal samples of the children were collected longitudinally. Using the Mullen Scales of Early Learning to assess cognition and the scores as the outcomes, linear mixed effects models including both the levels of eight HMOs and relative abundance of Bacteroides and Bifidobacterium species as main associations and their interactions were employed with adjusting covariates; infant sex, delivery mode, maternal education, site, and batch effects of HMOs. Additionally, regression models stratifying infants based on the A-tetrasaccharide (A-tetra) status of the HM they received were also employed to determine if the associations depend on the A-tetra status. With Bacteroides species, we observed significant associations with motor functions, while Bif. catenulatum showed a negative association with visual reception in the detectable A-tetra group both as main effect (value of p = 0.012) and in interaction with LNFP-I (value of p = 0.007). Additionally, 3-FL showed a positive association with gross motor (p = 0.027) and visual reception (p = 0.041). Furthermore, significant associations were observed with the interaction terms mainly in the undetectable A-tetra group. Specifically, we observed negative associations for Bifidobacterium species and LNT [breve (p = 0.011) and longum (p = 0.022)], and positive associations for expressive language with 3'-SL and Bif. bifidum (p = 0.01), 6'-SL and B. fragilis (p = 0.019), and LNFP-I and Bif. kashiwanohense (p = 0.048), respectively. Our findings suggest that gut microbiota and HMOs are both independently and interactively associated with early cognitive development. In particular, the diverse interactions between HMOs and Bacteroides and Bifidobacterium species reveal different candidate pathways through which HMOs, Bifidobacterium and Bacteroides species potentially interact to impact cognitive development in infancy.

The Effect of Human Milk Oligosaccharides and Bifidobacterium longum subspecies infantis Bi-26 on Simulated Infant Gut Microbiome and Metabolites

Human milk oligosaccharides (HMOs) shape the developing infant gut microbiota. In this study, a semi-continuous colon simulator was used to evaluate the effect of 2 HMOs-2'-fucosyllactose (2'-FL) and 3-fucosyllactose (3-FL)-on the composition of infant faecal microbiota and microbial metabolites. The simulations were performed with and without a probiotic Bifidobacterium longum subspecies infantis Bi-26 (Bi-26) and compared with a control that lacked an additional carbon source. The treatments with HMOs decreased α-diversity and increased Bifidobacterium species versus the control, but the Bifidobacterium species differed between simulations. The levels of acetic acid and the sum of all short-chain fatty acids (SCFAs) trended toward an increase with 2'-FL, as did lactic acid with 2'-FL and 3-FL, compared with control. A clear correlation was seen between the consumption of HMOs and the increase in SCFAs (-0.72) and SCFAs + lactic acid (-0.77), whereas the correlation between HMO consumption and higher total bifidobacterial numbers was moderate (-0.46). Bi-26 decreased propionic acid levels with 2'-FL. In conclusion, whereas infant faecal microbiota varied between infant donors, the addition of 2'-FL and 3-FL, alone or in combination, increased the relative abundance and numbers Bifidobacterium species in the semi-continuous colon simulation model, correlating with the production of microbial metabolites. These findings may suggest that HMOs and probiotics benefit the developing infant gut microbiota.

Structural characterization of a novel fucosylated trisaccharide prepared from bacterial exopolysaccharides and evaluation of its prebiotic activity

Fucosylated oligosaccharides have promising prospects in various fields. In this study, a fucosylated trisaccharide (GFG) was separated from the acidolysis products of exopolysaccharides from Clavibacter michiganensis M1. Structural characterization demonstrated that GFG consists of glucose, galactose, and fucose, with a molecular weight of 488 Da. Nuclear magnetic resonance analysis showed that it has a different structure than that of 2'-fucosyllactose (2'-FL), even though they have the same monosaccharide composition. In vitro prebiotic experiments were conducted to evaluate the differences in the utilization of three selected carbohydrates by fourteen bacterial strains. In comparison with 2'-FL, GFG could be utilized by more beneficial bacteria, leading to generate more short-chain fatty acids. Moreover, GFG could not promote the proliferation of Escherichia coli. This work describes a novel fucosylated oligosaccharide and its preparation method, and the obtained trisaccharide may serve as a promising candidate for fucosylated human milk oligosaccharides.

Nondigestible Functional Oligosaccharides: Enzymatic Production and Food Applications for Intestinal Health

Nondigestible functional oligosaccharides are of particular interest in recent years because of their unique prebiotic activities, technological characteristics, and physiological effects. Among different types of strategies for the production of nondigestible functional oligosaccharides, enzymatic methods are preferred owing to the predictability and controllability of the structure and composition of the reaction products. Nondigestible functional oligosaccharides have been proved to show excellent prebiotic effects as well as other benefits to intestinal health. They have exhibited great application potential as functional food ingredients for various food products with improved quality and physicochemical characteristics. This article reviews the research progress on the enzymatic production of several typical nondigestible functional oligosaccharides in the food industry, including galacto-oligosaccharides, xylo-oligosaccharides, manno-oligosaccharides, chito-oligosaccharides, and human milk oligosaccharides. Moreover, their physicochemical properties and prebiotic activities are discussed as well as their contributions to intestinal health and applications in foods.

Role of human milk oligosaccharide metabolizing bacteria in the development of atopic dermatitis/eczema

Despite affecting up to 20% of infants in the United States, there is no cure for atopic dermatitis (AD), also known as eczema. Atopy usually manifests during the first six months of an infant's life and is one predictor of later allergic health problems. A diet of human milk may offer protection against developing atopic dermatitis. One milk component, human milk oligosaccharides (HMOs), plays an important role as a prebiotic in establishing the infant gut microbiome and has immunomodulatory effects on the infant immune system. The purpose of this review is to summarize the available information about bacterial members of the intestinal microbiota capable of metabolizing HMOs, the bacterial genes or metabolic products present in the intestinal tract during early life, and the relationship of these genes and metabolic products to the development of AD/eczema in infants. We find that specific HMO metabolism gene sets and the metabolites produced by HMO metabolizing bacteria may enable the protective role of human milk against the development of atopy because of interactions with the immune system. We also identify areas for additional research to further elucidate the relationship between the human milk metabolizing bacteria and atopy. Detailed metagenomic studies of the infant gut microbiota and its associated metabolomes are essential for characterizing the potential impact of human milk-feeding on the development of atopic dermatitis.

Breastfeeding and the major fermentation metabolite lactate determine occurrence of Peptostreptococcaceae in infant feces

Previous studies indicated an intrinsic relationship between infant diet, intestinal microbiota composition and fermentation activity with a strong focus on the role of breastfeeding on microbiota composition. Yet, microbially formed short-chain fatty acids acetate, propionate and butyrate and other fermentation metabolites such as lactate not only act as substrate for bacterial cross-feeding and as mediators in microbe-host interactions but also confer antimicrobial activity, which has received considerably less attention in the past research. It was the aim of this study to investigate the nutritional-microbial interactions that contribute to the development of infant gut microbiota with a focus on human milk oligosaccharide (HMO) fermentation. Infant fecal microbiota composition, fermentation metabolites and milk composition were analyzed from 69 mother-infant pairs of the Swiss birth cohort Childhood AlleRgy nutrition and Environment (CARE) at three time points depending on breastfeeding status defined at the age of 4 months, using quantitative microbiota profiling, HPLC-RI and 1H-NMR. We conducted in vitro fermentations in the presence of HMO fermentation metabolites and determined the antimicrobial activity of lactate and acetate against major Clostridiaceae and Peptostreptococcaceae representatives. Our data show that fucosyllactose represented 90% of the HMOs present in breast milk at 1- and 3-months post-partum with fecal accumulation of fucose, 1,2-propanediol and lactate indicating fermentation of HMOs that is likely driven by Bifidobacterium. Concurrently, there was a significantly lower absolute abundance of Peptostreptococcaceae in feces of exclusively breastfed infants at 3 months. In vitro, lactate inhibited strains of Peptostreptococcaceae. Taken together, this study not only identified breastfeeding dependent fecal microbiota and metabolite profiles but suggests that HMO-derived fermentation metabolites might exert an inhibitory effect against selected gut microbes.

Efficacy of Bifidobacterium longum alone or in multi-strain probiotic formulations during early life and beyond

The significance of Bifidobacterium to human health can be appreciated from its early colonization of the neonatal gut, where Bifidobacterium longum represents the most abundant species. While its relative abundance declines with age, it is further reduced in several diseases. Research into the beneficial properties of B. longum has unveiled a range of mechanisms, including the production of bioactive molecules, such as short-chain fatty acids, polysaccharides, and serine protease inhibitors. From its intestinal niche, B. longum can have far-reaching effects in the body influencing immune responses in the lungs and even skin, as well as influencing brain activity. In this review, we present the biological and clinical impacts of this species on a range of human conditions beginning in neonatal life and beyond. The available scientific evidence reveals a strong rationale for continued research and further clinical trials that investigate the ability of B. longum to treat or prevent a range of diseases across the human lifespan.

Characterization and stabilization of the α-L-fucosidase set from Lacticaseibacillus rhamnosus INIA P603

This study describes the molecular identification, biochemical characterization, and stabilization of three recombinant AlfA, AlfB, and AlfC fucosidases from Lacticaseibacillus rhamnosus INIA P603. Even though previous studies revealed the presence of fucosidase activity in L. rhamnosus extracts, the identification of the fucosidases, their physicochemical properties, and the substrate spectrum remained unknown. Although the presence of alfB is not common in strains of L. rhamnosus, fucosidases from L. rhamnosus INIA P603 were selected because this strain exhibited higher fucosidase activity in culture and the complete set of fucosidases. A high yield of purified recombinant AlfA, AlfB, and AlfC fucosidases was obtained (8, 12, and 18 mg, respectively). AlfA, AlfB, and AlfC showed their optimal activities at pH 5.0 and 4.0 at 60 °C, 40 °C, and 50 °C, respectively. Unlike 3-fucosyllactose, all three recombinant fucosidases were able to hydrolyze 2'-fucosyllactose (2'-FL), and their activities were improved through their immobilization on agarose supports. Nevertheless, immobilized AlfB exhibited the highest hydrolysis, releasing 39.6 µmol of fucose mg enzyme^-1 min^-1. Only the immobilized AlfB was able to synthetize 2'-FL. In conclusion, the enzymatic properties elucidated in this study support the potential ability of fucosidases from L. rhamnosus INIA P603 to hydrolyze fucosylated substrates as well as justifying interest for further research into AlfB for its application to catalyze the synthesis of fucosylated prebiotics. KEY POINTS: • Few strains of L. rhamnosus exhibited alfB on their chromosomes. • Fucosidases from L. rhamnosus INIA P603 were characterized and stabilized. • Although all the fucosidases hydrolyzed 2'-FL, only AlfB transfucosylated lactose.

Recent Research and Application Prospect of Functional Oligosaccharides on Intestinal Disease Treatment

The intestinal tract is an essential digestive organ of the human body, and damage to the intestinal barrier will lead to various diseases. Functional oligosaccharides are carbohydrates with a low degree of polymerization and exhibit beneficial effects on human intestinal health. Laboratory experiments and clinical studies indicate that functional oligosaccharides repair the damaged intestinal tract and maintain intestinal homeostasis by regulating intestinal barrier function, immune response, and intestinal microbial composition. Functional oligosaccharides treat intestinal disease such as inflammatory bowel disease (IBD) and colorectal cancer (CRC) and have excellent prospects for therapeutic application. Here, we present an overview of the recent research into the effects of functional oligosaccharides on intestinal health.

The development of human gut microbiota fermentation capacity during the first year of life

Fermentation capacity of microbial ecosystems intrinsically depends on substrate supply and the ability of a microbial community to deliver monomers for fermentation. In established microbial ecosystems, the microbial community is adapted to efficiently degrade and ferment available biopolymers which is often concurrently reflected in the richness of the microbial community and its functional potential. During the first year of life, the human gut microbial environment is a rather dynamic system that is characterized by a change in physiological conditions (e.g. from aerobic to anaerobic conditions, physical growth of the gastrointestinal tract, development of the intestinal immune system) but also by a change in nutrient supply from a compositionally limited liquid to a diverse solid diet, which demands major compositional and functional changes of the intestinal microbiota. How these transitions link to intestinal microbial fermentation capacity has gained comparatively little interest so far. This mini-review aims to collect evidence that already after birth, there is seeding of a hidden population of various fermentation organisms which remain present at low abundance until the cessation of breastfeeding removes nutritional restrictions of a liquid milk-based diet. The introduction of solid food containing plant and animal material is accompanied by an altering microbiota. The concurrent increases in the abundance of degraders and fermenters lead to higher intestinal fermentation capacity indicated by increased faecal levels of the final fermentation metabolites propionate and butyrate. Recent reports indicate that the development of fermentation capacity is an important step during gut microbiota development, as chronic disorders such as allergy and atopic dermatitis have been linked to lower degradation and fermentation capacity indicated by reduced levels of final fermentation metabolites at 1 year of age.

Synergy between oligosaccharides and probiotics: From metabolic properties to beneficial effects

Synbiotic is defined as the dietary mixture that comprises both probiotic microorganisms and prebiotic substrates. The concept has been steadily gaining attention owing to the rising recognition of probiotic, prebiotics, and gut health. Among prebiotic substances, oligosaccharides demonstrated considerable health beneficial effects in varieties of food products and their combination with probiotics have been subjected to full range of evaluations. This review delineated the landscape of studies using microbial cultures, cell lines, animal model, and human subjects to explore the functional properties and host impacts of these combinations. Overall, the results suggested that these combinations possess respective metabolic properties that could facilitate beneficial activities therefore could be employed as dietary interventions for human health improvement and therapeutic purposes. However, uncertainties, such as applicational practicalities, underutilized analytical tools, contradictory results in studies, unclear mechanisms, and legislation hurdles, still challenges the broad utilization of these combinations. Future studies to address these issues may not only advance current knowledge on probiotic-prebiotic-host interrelationship but also promote respective applications in food and nutrition.

2'-Fucosyllactose Suppresses Angiogenesis and Alleviates Toxic Effects of 5-Fu in a HCT116 Colon Tumor-Bearing Model

The present study was aimed at examining the anti-tumor effects and molecular mechanisms of 2'-fucosyllactose (2'-FL). At the beginning, the viabilities of four types of colon cancer cells were analyzed after exposure to increasing concentrations of 2'-FL, and HCT116 cells were selected as the sensitive ones, which were applied in the further experiments; then, interestingly, 2'-FL (102.35 µM) was found to induce apoptosis of HCT116 cells, which coincides with significant changes in VEGFA/VEGFR2/p-PI3K/p-Akt/cleaved Caspase3 proteins. Next, in a tumor-bearing nude mouse model, HCT116 was chosen as the sensitive cell line, and 5-fluorouracil (5-Fu) was chosen as the positive medicine. It was noteworthy that both 2'-FL group (2.41 ± 0.57 g) and 2'FL/5-Fu group (1.22 ± 0.35 g) had a significantly lower tumor weight compared with the control (3.87 ± 0.79 g), suggesting 2'-FL could inhibit colon cancer. Since 2'-FL reduced the number of new blood vessels and the malignancy of tumors, we confirmed that 2'-FL effectively inhibited HCT116 tumors, and its mechanism was achieved by regulating the VEGFA/VEGFR2/PI3K/Akt/Caspase3 pathway. Moreover, though HE staining and organ index measurement, 2'-FL was validated to alleviate toxic effects on liver and kidney tissue when combining with 5-Fu. In conclusion, 2'-FL had certain anti-tumor and detoxification effects.

2'-Fucosyllactose Remits Colitis-Induced Liver Oxygen Stress through the Gut-Liver-Metabolites Axis

Liver oxygen stress is one of the main extraintestinal manifestations of colitis and 5% of cases develop into a further liver injury and metabolic disease. 2′-fucosyllactose (2′-FL), a main member of human milk oligosaccharides (HMOs), has been found to exert efficient impacts on remitting colitis. However, whether 2′-FL exerts the function to alleviate colitis-induced liver injury and how 2′-FL influences the metabolism via regulating gut microbiota remain unknown. Herein, in our study, liver oxygen stress was measured by measuring liver weight and oxygen-stress-related indicators. Then, 16S full-length sequencing analysis and non-target metabolome in feces were performed to evaluate the overall responses of metabolites and intestinal bacteria after being treated with 2′-FL (400 mg/kg b.w.) in colitis mice. The results showed that, compared with the control group, the liver weight of colitis mice was significantly decreased by 18.30% (p < 0.05). After 2′-FL treatment, the liver weight was significantly increased by 12.65% compared with colitis mice (p < 0.05). Meanwhile, they exhibited higher levels of oxidation in liver tissue with decreasing total antioxidant capacity (T-AOC) (decreased by 17.15%) and glutathione (GSH) levels (dropped by 22.68%) and an increasing malondialdehyde (MDA) level (increased by 36.24%), and 2′-FL treatment could reverse those tendencies. Full-length 16S rRNA sequencing revealed that there were 39 species/genera differentially enriched in the control, dextran sulphate sodium (DSS), and DSS + 2′-FL groups. After treatment with 2′-FL, the intestinal metabolic patterns, especially glycometabolism and the lipid-metabolism-related process, in DSS mice were strikingly altered with 33 metabolites significantly down-regulated and 26 metabolites up-regulated. Further analysis found DSS induced a 40.01%, 41.12%, 43.81%, and 39.86% decline in acetic acid, propionic acid, butyric acid, and total short chain fatty acids (SCFAs) in colitis mice (all p < 0.05), respectively, while these were up-regulated to different degrees in the DSS + 2′-FL group. By co-analyzing the data of gut microbiota and metabolites, glycometabolism and lipid-metabolism-associated metabolites exhibited strong positive/negative relationships with Akkermansia_muciniphila (all p < 0.01) and Paraprevotella spp. (all p < 0.01), suggesting that the two species might play crucial roles in the process of 2′-FL alleviating colitis-induced liver oxygen stress. In conclusion, in the gut−liver−microbiotas axis, 2′-FL mediated in glucose and lipid-related metabolism and alleviated liver oxygen stress via regulating gut microbiota in the DSS-induced colitis model. The above results provide a new perspective to understand the probiotic function of 2′-FL.

Isolation and purification of Tartary buckwheat polysaccharides and their effect on gut microbiota

Tartary buckwheat (Fagopyrum tataricum) is rich in polysaccharides that can be utilized by the gut microbiota (GM) and provide several health benefits. However, the mechanisms underlying the action of these polysaccharides remain unclear to date. In this study, Tartary buckwheat polysaccharides (TBP) were purified, and five fractions were obtained. The composition of these fractions was determined using ion chromatography. Different TBP components were investigated regarding their probiotic effect on three species of Bifidobacteria and Lactobacillus rhamnosus. In addition, the effect of TBP on GM and short-chain fatty acids (SCFAs) was evaluated. Results showed that the probiotic effect of TBP fraction was dependent on their composition. The polysaccharides present in different fractions had specific probiotic effects. TBP-1.0, mainly composed of fucose, glucose, and d-galactose, exhibited the strongest proliferation effect on L. rhamnosus, while TBP-W, rich in glucose, d-galactose, and fructose, had the best promoting effect on Bifidobacterium longum and Bifidobacterium adolescentis growth. Furthermore, TBP-0.2, composed of d-galacturonic acid, d-galactose, xylose, and arabinose, exhibited its highest impact on Bifidobacterium breve growth. The composition of GM was significantly altered by adding TBP during fecal fermentation, with an increased relative abundance of Lactococcus, Phascolarctobacterium, Bacteroidetes, and Shigella. Simultaneously, the level of SCFA was also significantly increased by TBP. Our findings indicate that Tartary buckwheat can provide specific dietary polysaccharide sources to modulate and maintain GM diversity. They provide a basis for Tartary buckwheat commercial utilization for GM modulation.

In Vitro Infant Fecal Fermentation Characteristics of Human Milk Oligosaccharides Were Controlled by Initial Microbiota Composition More than Chemical Structure

SCOPE

Human milk oligosaccharides (HMOs), multifunctional glycans naturally present in human milk, are known to contribute to the infant's microbiota and immune system development. However, the molecular specificity of HMOs on microbiota and associated fermentation is not yet fully understood, and is important for the development of infant formula optimum functionality.

METHODS AND RESULTS

In vitro fermentation is carried out on structurally different HMOs with infant fecal inocula dominated by Bifidobacterium longum, Bifidobacterium breve, and Bacteroides. The gas, metabolite (SCFA, lactate, and succinate) profiles, and microbiota responses differ between individual microbiota inocula patterns regardless of HMO structure. In terms of HMO pairs with same sugar composition but different glycosidic bonds, gas and metabolite profiles are similar with the B. longum- and B. breve-dominated inocula. However, large individual variations are observed with the Bacteroides-dominated inocula. The microbial communities at the end of fermentation are closely related to the initial microbiota composition.

CONCLUSION

The findings demonstrate that short-term in vitro fermentation outcomes largely depend on the initial gut microbiota composition more than the impact of HMO molecular specificity. These results advance the current understanding for the design of personalized infant nutritional solutions and therapies in future.

2'-Fucosyllactose Increases the Abundance of Blautia in the Presence of Extracellular Fucosidase-Possessing Bacteria

Blautia is a genus of anaerobic bacteria that is widely distributed in the mammalian gut. Recently, an increasing body of research has demonstrated a link between this genus and human health, suggesting applications as a novel probiotic strain. Moreover, we have previously shown that 2'-fucosyllactose (2'-FL), a major component of human milk oligosaccharides, increases the relative abundance of Blautia sp., particularly Blautia wexlerae, in the cultured fecal microbiota of healthy adults using a pH-controlled single-batch fermenter. However, the effects of 2'-FL on Blautia proliferation vary among individuals. In this study, we assessed the impact of the intrinsic gut microbiota on the prebiotic effects of 2'-FL. Metagenomic analysis of feces collected from all donors showed that the homolog of the intracellular GH95 α-l-fucosidase gene was considerably enriched in two non-responders (individuals who showed no increase in Blautia proliferation), whereas the homologous genes encoding extracellular α-l-fucosidase were more abundant in responders, suggesting that lactose and fucose released into the environment could be substrates mediating the growth of Blautia. In vitro assays confirmed the ability of B. wexlerae to utilize the two carbohydrates but not 2'-FL. We also observed that B. wexlerae utilized fucose released from 2'-FL by Bifidobacterium bifidum, which possessed extracellular GH95 α-l-fucosidase, in co-cultures of these two organisms. Finally, increasing the proportion of extracellular GH95 by the addition of a B. bifidum strain led to Blautia proliferation by 2'-FL in fecal cultures of the two non-responders. These findings provided valuable perspectives on individualized nutritional approaches to properly control the gut microbiota. Future clinical trials are needed to obtain further insights into the characteristics of responders vs. non-responders.

Combining galacto-oligosaccharides and 2'-fucosyllactose alters their fermentation kinetics by infant fecal microbiota and influences AhR-receptor dependent cytokine responses in immature dendritic cells

Galacto-oligosaccharides (GOS) and 2′-fucosyllactose (2′-FL) are non-digestible carbohydrates (NDCs) that are often added to infant formula to replace the functionalities of human milk oligosaccharides (HMOs). It is not known if combining GOS and 2′-FL will affect their fermentation kinetics and subsequent immune-modulatory effects such as AhR-receptor stimulation. Here, we used an in vitro set-up for the fermentation of 2′-FL and GOS, either individually or combined, by fecal microbiota of 8-week-old infants. We found that GOS was fermented two times faster by the infant fecal microbiota when combined with 2′-FL, while the combination of GOS and 2′-FL did not result in a complete degradation of 2′-FL. Fermentation of both GOS and 2′-FL increased the relative abundance of Bifidobacterium, which coincided with the production of acetate and lactate. Digesta of the fermentations influenced dendritic cell cytokine secretion differently under normal conditions and in the presence of the AhR-receptor blocker CH223191. We show that, combining GOS and 2′-FL accelerates GOS fermentation by the infant fecal microbiota of 8-week-old infants. In addition, we show that the fermentation digesta of GOS and 2′-FL, either fermented individually or combined, can attenuate DC cytokine responses in a similar and in an AhR-receptor dependent way.

Galacto-oligosaccharides (GOS) and 2′-fucosyllactose (2′-FL) are non-digestible carbohydrates (NDCs) that are often added to infant formula to replace the functionalities of human milk oligosaccharides (HMOs).