In this paper we use continuum modeling to analyze the mechanism of the oxygen reduction reaction at a porous mixed-conducting oxygen electrode. We show that for La0 5(Ca, Sr)04Fe08Co0203,, at 700°C, solid-state oxygen diffusion and 02 surface exchange dominate the electrochemical behavior, producing effective "chemical" resistances and capacitances. This behavior can be explained both qualitatively and quantitatively in terms of the known bulk and surface properties of the materials. This mechanism appears to be generally valid for mixed conductors with high rates of internal mass transfer, but breaks down for mixed conductors that have poor ionic transport. Our analysis also suggests that, for the best electrode materials, extension of the reaction zone beyond the three-phase boundary is limited to a few micrometers. We also show that gas phase diffusion resistance can contribute significantly to cell impedance at P0 0.1 atm. InfroductionElectrode reactions in solid-state electrochemical systems involve a complex interaction of mobile electronic, ionic, and molecular species. One example that has drawn

The present study was conducted to obtain a comprehensive overview of oligosaccharides present in the milk of a variety of important domestic animals including cows, goats, sheep, pigs, horses and dromedary camels. Using an analytical workflow that included ultraperformance liquid chromatography -hydrophilic interaction liquid chromatography with fluorescence detection coupled to quadrupole time-of-flight MS, detailed oligosaccharide libraries were established. The partial or full characterisation of the neutral/fucosylated, phosphorylated and sialylated structures was facilitated by sequencing with linkage-and sugar-specific exoglycosidases. Relative peak quantification of the 2-aminobenzamide-labelled oligosaccharides provided additional information. Milk from domestic animals contained a much larger variety of complex oligosaccharides than was previously assumed, and thirteen of these structures have been identified previously in human milk. The direct comparison of the oligosaccharide mixtures reflects their role in the postnatal maturation of different types of gastrointestinal systems, which, in this way, are prepared for certain post-weaning diets. The potential value of animal milk for the commercial extraction of oligosaccharides to be used in human and animal health is highlighted.Key words: Domestic animal milk: Oligosaccharides: Ultra-performance liquid chromatography -hydrophilic interaction liquid chromatography with fluorescence detection -MS: 2-Aminobenzamide: Relative quantification Human milk and animal milk are rich sources of bioactive oligosaccharides, which are of great interest to the functional food industry. Many biological activities have been reported for certain milk oligosaccharides including prebiotic activity, anti-adhesion effects, anti-inflammatory properties, glycomemodifying activity, and a role in brain development and growth-related characteristics of intestinal cells (1 -4) . Milk oligosaccharides are typically composed of three to ten monosaccharide units, including glucose (Glc), galactose (Gal) and N-acetyl-glucosamine (GlcNAc) as well as fucose and sialic acids. The core unit present at the reducing end of milk oligosaccharides is either lactose (Gal(b1 -4)Glc) or N-acetyl-lactosamine (Gal(b1 -4)GlcNAc) (5) .As the biological activity of milk oligosaccharides is dependent on their individual structural characteristics, a detailed knowledge of their composition is necessary. Human milk is a rich source of oligosaccharides (20 mg/l in colostrum; 12 -13 mg/l in mature milk), and more than 200 structures have been identified so far (6,7) . Less is known about animal milk oligosaccharides as their concentration in milk is low. For example, the concentration of oligosaccharides in bovine colostrum is 1 g/l, whereas their concentration in mature milk is about 20-fold less (8,9) . Using a combination of advanced analytical techniques, structural libraries of up to forty and even more than fifty bovine milk oligosaccharides (10 -12) , twenty-nine porcine milk oligosacch...

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Bifidobacteria are common and frequently dominant members of the gut microbiota of many animals, including mammals and insects. Carbohydrates are considered key carbon sources for the gut microbiota, imposing strong selective pressure on the complex microbial consortium of the gut. Despite its importance, the genetic traits that facilitate carbohydrate utilization by gut microbiota members are still poorly characterized. Here, genome analyses of 47 representative Bifidobacterium (sub)species revealed the genes predicted to be required for the degradation and internalization of a wide range of carbohydrates, outnumbering those found in many other gut microbiota members. The glycan-degrading abilities of bifidobacteria are believed to reflect available carbon sources in the mammalian gut. Furthermore, transcriptome profiling of bifidobacterial genomes supported the involvement of various chromosomal loci in glycan metabolism. The widespread occurrence of bifidobacterial saccharolytic features is in line with metagenomic and metatranscriptomic datasets obtained from human adult/infant faecal samples, thereby supporting the notion that bifidobacteria expand the human glycobiome. This study also underscores the hypothesis of saccharidic resource sharing among bifidobacteria through species-specific metabolic specialization and cross feeding, thereby forging trophic relationships between members of the gut microbiota.

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