Selected fructooligosaccharide composition of pet-food ingredients

Harvesting of Prebiotic Fructooligosaccharides by Nonbeneficial Human Gut Bacteria

Prebiotics are increasingly used as food supplements, especially in infant formulas, to modify the functioning and composition of the microbiota. However, little is currently known about the mechanisms of prebiotic recognition and transport by gut bacteria, while these steps are crucial in their metabolism. In this study, we established a new strategy to profile the specificity of oligosaccharide transporters, combining microbiomics, genetic locus and strain engineering, and state-of-the art metabolomics. We revisited the transporter classification database and proposed a new way to classify these membrane proteins based on their structural and mechanistic similarities. Based on these developments, we identified and characterized, at the molecular level, a fructooligosaccharide transporting phosphotransferase system, which constitutes a biomarker of diet and gut pathology. The deciphering of this prebiotic metabolization mechanism by a nonbeneficial bacterium highlights the controversial use of prebiotics, especially in the context of chronic gut diseases.

Prebiotic oligosaccharides, such as fructooligosaccharides, are increasingly being used to modulate the composition and activity of the gut microbiota. However, carbohydrate utilization analyses and metagenomic studies recently revealed the ability of deleterious and uncultured human gut bacterial species to metabolize these functional foods. Moreover, because of the difficulties of functionally profiling transmembrane proteins, only a few prebiotic transporters have been biochemically characterized to date, while carbohydrate binding and transport are the first and thus crucial steps in their metabolization. Here, we describe the molecular mechanism of a phosphotransferase system, highlighted as a dietary and pathology biomarker in the human gut microbiome. This transporter is encoded by a metagenomic locus that is highly conserved in several human gut Firmicutes, including Dorea species. We developed a generic strategy to deeply analyze, in vitro and in cellulo, the specificity and functionality of recombinant transporters in Escherichia coli, combining carbohydrate utilization locus and host genome engineering and quantification of the binding, transport, and growth rates with analysis of phosphorylated carbohydrates by mass spectrometry. We demonstrated that the Dorea fructooligosaccharide transporter is specific for kestose, whether for binding, transport, or phosphorylation. This constitutes the biochemical proof of effective phosphorylation of glycosides with a degree of polymerization of more than 2, extending the known functional diversity of phosphotransferase systems. Based on these new findings, we revisited the classification of these carbohydrate transporters.

IMPORTANCE Prebiotics are increasingly used as food supplements, especially in infant formulas, to modify the functioning and composition of the microbiota. However, little is currently known about the mechanisms of prebiotic recognition and transport by gut bacteria, while these steps are crucial in their metabolism. In this study, we established a new strategy to profile the specificity of oligosaccharide transporters, combining microbiomics, genetic locus and strain engineering, and state-of-the art metabolomics. We revisited the transporter classification database and proposed a new way to classify these membrane proteins based on their structural and mechanistic similarities. Based on these developments, we identified and characterized, at the molecular level, a fructooligosaccharide transporting phosphotransferase system, which constitutes a biomarker of diet and gut pathology. The deciphering of this prebiotic metabolization mechanism by a nonbeneficial bacterium highlights the controversial use of prebiotics, especially in the context of chronic gut diseases.

Nutrient composition and digestibility of energy and nutrients in wheat middlings and red dog fed to growing pigs

This experiment was designed to determine nutrient composition and apparent total tract digestibility (ATTD) of GE, DM, OM, and NDF and the concentration of DE and ME in 10 sources of wheat middlings and in 1 source of red dog that were obtained from different flour mills in the United States. Twelve growing pigs (initial BW: 31.0 ± 1.0 kg) were randomly allotted to a 12 × 8 Youden square design with 12 dietary treatments and eight 14 d periods. Pigs were individually housed in metabolism crates for total collection of feces and urine. A basal diet based on corn and soybean meal, and 11 diets containing corn, soybean meal, and 39.4% of one of the 10 sources of wheat middlings or of red dog were formulated. The ATTD of GE, DM, OM, and NDF in all diets was calculated using the direct procedure, and the ATTD of GE, DM, OM, and NDF in each source of wheat middlings or red dog was calculated by difference. Values for DE and ME were calculated as well. The average concentration of CP was 17.67% in wheat midlings and 17.0% in red dog, and the concentration of acid hydrolyzed ether extract (AEE) and total dietary fiber (TDF) was 2.44 and 13.90% in red dog, but 4.07 and 36.45% in wheat middlings. Red dog also contained more starch (42.98%) than wheat middlings (20.28%). Red dog had greater bulk density (498.5 g/L) and smaller particle size (146 µm) compared with wheat middlings (315.1 g/L and 783 µm). The average ATTD of GE, DM, OM, and NDF in wheat middlings (67.2%, 71.2%, 72.9%, and 53.0%, respectively) was less (P < 0.05) than in red dog (79.35%, 82.9%, 86.6%, and 58.7%, respectively). The average concentrations of DE and ME in wheat middlings were 2,990 and 2,893 kcal/kg DM, and these values were less (P < 0.05) than the DE and ME in red dog (3,408 and 3,292 kcal/kg DM). In conclusion, wheat middlings contains more fiber and less starch than red dog and the ATTD of GE and nutrients is greater in red dog than in wheat middlings. As a consequence, concentrations of DE and ME are greater in red dog than in wheat middlings.

Effects of dietary raffinose on growth, non-specific immunity, intestinal morphology and microbiome of juvenile hybrid sturgeon (Acipenser baeri Brandt ♀ × A. schrenckii Brandt ♂)

This study was performed to determine the efficacy of raffinose on the growth, non-specific immunity, intestinal morphology and microbiota of juvenile hybrid sturgeon, (Acipenser baeri Brandt ♀ × A. schrenckii Brandt ♂). Hybrid sturgeons were divided into 2 groups and each group was fed with diets supplemented with or without raffinose for 56 days. Hybrid sturgeon fed diet supplemented with raffinose had significantly higher final body weight (FBW), specific growth rate (SGR), and weight gain ratio (WGR) than fish fed the control diet (P < 0.05). Raffinose in diet had no negative effect on feed intake (FI) and feed conversion ratio (FCR) (P > 0.05). Compared with the control diet, the myeloperoxidase (MPO) and respiratory burst (NBT) activitives were significantly higher in sturgeon fed the raffinose supplemented diet (P < 0.05). The increasing of intestinal villi area and mucosal folds were observed in intestinal tract of sturgeon when they fed the raffinose supplemented diet. Meanwhile, the residual bait of intestinal tract was relatively lower in sturgeon with raffinose treatment. High-throughput sequencing revealed that majority of reads derived from the sturgeon digesta were constituted by members of Proteobacteria, Firmicutes, Fusobacteria and Actinobacteria. Shannon's diversity index existed significant difference among dietary treatments indicating that the overall microbial community was modified to a large extent by dietary raffinose. In conclusion, supplementation of the diet with raffinose is capable of improving hybrid sturgeon growth performances and intestinal morphology, modifying the intestinal microbial composition.

Defined Nutrient Diets Alter Susceptibility to Clostridium difficile Associated Disease in a Murine Model

Background

Clostridium difficile is a major identifiable and treatable cause of antibiotic-associated diarrhea. Poor nutritional status contributes to mortality through weakened host defenses against various pathogens. The primary goal of this study was to assess the contribution of a reduced protein diet to the outcomes of C. difficile infection in a murine model.

Methods

C57BL/6 mice were fed a traditional house chow or a defined diet with either 20% protein or 2% protein and infected with C. difficile strain VPI10463. Animals were monitored for disease severity, clostridial shedding and fecal toxin levels. Select intestinal microbiota were measured in stool and C. difficile growth and toxin production were quantified ex vivo in intestinal contents from untreated or antibiotic-treated mice fed with the different diets.

Results

C. difficile infected mice fed with defined diets, particularly (and unexpectedly) with protein deficient diet, had increased survival, decreased weight loss, and decreased overall disease severity. C. difficile shedding and toxin in the stool of the traditional diet group was increased compared with either defined diet 1 day post infection. Mice fed with traditional diet had an increased intestinal Firmicutes to Bacteroidetes ratio following antibiotic exposure compared with either a 2% or 20% protein defined nutrient diet. Ex vivo inoculation of cecal contents from antibiotic-treated mice showed decreased toxin production and C. difficile growth in both defined diets compared with a traditional diet.

Conclusions

Low protein diets, and defined nutrient diets in general, were found to be protective against CDI in mice. Associated diet-induced alterations in intestinal microbiota may influence colonization resistance and clostridial toxin production in a defined nutrient diet compared to a traditional diet, leading to increased survival. However, mechanisms which led to survival differences between 2% and 20% protein defined nutrient diets need to be further elucidated.

Dietary modulation of the human colonic microbiota: updating the concept of prebiotics

Prebiotics are non-digestible (by the host) food ingredients that have a beneficial effect through their selective metabolism in the intestinal tract. Key to this is the specificity of microbial changes. The present paper reviews the concept in terms of three criteria: (a) resistance to gastric acidity, hydrolysis by mammalian enzymes and gastrointestinal absorption; (b) fermentation by intestinal microflora; (c) selective stimulation of the growth and/or activity of intestinal bacteria associated with health and wellbeing. The conclusion is that prebiotics that currently fulfil these three criteria are fructo-oligosaccharides, galacto-oligosaccharides and lactulose, although promise does exist with several other dietary carbohydrates. Given the range of food vehicles that may be fortified by prebiotics, their ability to confer positive microflora changes and the health aspects that may accrue, it is important that robust technologies to assay functionality are used. This would include a molecular-based approach to determine flora changes. The future use of prebiotics may allow species-level changes in the microbiota, an extrapolation into genera other than the bifidobacteria and lactobacilli, and allow preferential use in disease-prone areas of the body.

Regulation of fructooligosaccharide metabolism in an extra-intestinal pathogenic Escherichia coli strain

A gene cluster involved in the metabolism of prebiotic short-chain fructooligosaccharides (scFOS) has recently been identified in the extra-intestinal avian pathogenic Escherichia coli strain BEN2908. This gene cluster, called the fos locus, plays a major role in the initiation stage of chicken intestinal colonization. This locus is composed of six genes organized as an operon encoding a sugar transporter and enzymes involved in scFOS metabolism, and of a divergently transcribed gene encoding a transcriptional regulator, FosR, belonging to the LacI/GalR family. To decipher the regulation of scFOS metabolism, we monitored the fos operon promoter activity using a luciferase reporter gene assay. We demonstrated that the expression of fos genes is repressed by FosR, controlled by catabolite repression and induced in the presence of scFOS. Using electrophoretic mobility shift assays and surface plasmon resonance experiments, we showed that FosR binds to two operator sequences of the fos operon promoter region. This binding to DNA was inhibited in the presence of scFOS, especially by GF2. We then propose a model of scFOS metabolism regulation in a pathogenic bacterium, which will help to identify the environmental conditions required for fos gene expression and to understand the role of this locus in intestinal colonization.

Pet food and feed applications of inulin, oligofructose and other oligosaccharides

Prebiotics may be considered as functional food ingredients. They are attracting considerable interest from pet owners, pet food manufacturers, livestock producers and feed manufacturers. The most common forms of prebiotics are nondigestible oligosaccharides (NDO), including inulin, oligofructose mannanoligosaccharides, gluco-oligosaccharides, and galacto-oligosaccharides. These NDO are nondigestible by enzymes present in the mammalian small intestine, but are fermented by bacteria present in the hindgut of nonruminants. Inulin and oligofructose are present in measurable quantities in feed ingredients like wheat, wheat by-products, barley, and peanut hulls. Consumption of prebiotic oligosaccharides elicits several purported health benefits. In companion animals, prebiotics have been shown to improve gut microbial ecology and enhance stool quality. In production livestock and poultry, prebiotics are employed to control pathogenic bacteria, reduce faecal odour, and enhance growth performance. Research to date indicates positive effects of prebiotics on health status and performance of companion animals, livestock, and poultry.

Faecal bacterial profile, nitrogen excretion and mineral absorption in healthy dogs fed supplemental oligofructose

In a cross-over trial, five healthy dogs were fed a dry food without or with 1% (w/w) oligofructose to assess any oligofructose-induced effects on the faecal bacterial profile, nitrogen excretion and mineral absorption. The diets were given for a period of 3 weeks. Oligofructose feeding significantly raised the number of Bifidobacteria, Streptococci and Clostridia in faeces. The numbers of faecal anaerobic and aerobic bacteria were raised after ingestion of oligofructose. The faecal pH was unchanged. There was no effect of oligofructose feeding on the route of nitrogen excretion which was associated with a lack of effect on faecal ammonium and urinary urea excretion. It is suggested that the absence or presence of an effect of oligofructose on urinary and faecal nitrogen excretion depends on the background composition of the diet, in particular the content of non-digestible, fermentable carbohydrates. In the diets used, the content of non-digestible, fermentable carbohydrates was not measured. Both apparent magnesium and calcium absorption were significantly raised by oligofructose feeding, but phosphorus absorption was unaffected. The data presented may contribute to the qualification of the use of oligofructose in dog foods.

The effect of oligofructose and inulin on faecal characteristics and nutrient digestibility in healthy cats

The effects on faecal characteristics of different concentrations of oligofructose (0, 3, 6 and 9%) were investigated. The 6 and 9% supplemented groups differed significantly compared with the control group in almost all faecal characteristics. There were no significant differences regarding the macroscopical and chemical aspects of the faeces between the control and the 3% supplemented group. There was a trend for a lower pH of the faeces in the 3% supplemented group, suggesting a substantial effect on the faecal composition. In a second experiment, the effects of oligofructose (3%) and inulin (3 and 6%) on digestibility parameters were tested. In the supplemented groups the apparent protein digestibility was lower but this was due to a higher bacterial nitrogen content of the faeces. There were no significant differences between 3% inulin and oligofructose, although oligofructose seemed to be more easily fermentable, because of a trend to a higher concentration of short chain fatty acids (SCFA) in the faeces of the oligofructose group.

Petfood applications of inulin and oligofructose

Published data on intestinal microbiota of dogs and cats are limited but suggest the presence of a complex and diverse colonic bacterial population (34 genera including 129 species) the majority of which are anaerobes. During the colonic fermentation of endogenous and undigested amino acids, several putrefactive compounds (i.e., ammonia, aliphatic amines, indoles, phenols and volatile sulfur-containing compounds) are produced and are responsible for the malodor of dog and cat feces. These fecal odor components also have been implicated as causes of colorectal cancer; therefore, dietary manipulation of gut microbiota towards a potentially more remedial community (Bifidobacterium and Lactobacillus) is gaining more attention. The health benefits derived from dietary supplementation of prebiotics (e.g., oligofructose and inulin) have been documented in humans. However, little is known of a potentially similar role in companion animals. Feeding another prebiotic (i.e., lactosucrose) to dogs or cats is reported to increase the numbers of bifidobacteria and decrease the numbers of pathogens and the concentration of fecal odor components. In our laboratory, oligofructose supplementation numerically decreased the concentrations of ammonia and amines and increased the numbers of bifidobacteria in dog feces.