Bifidobacterium adolescentis possesses several arabinofuranosidases able to hydrolyze arabinoxylans (AX) and AX oligosaccharides (AXOS), the latter being bifidogenic carbohydrates with potential prebiotic properties. We characterized two new recombinant arabinofuranosidases, AbfA and AbfB, and AXH-d3, a previously studied arabinofuranosidase from B. adolescentis. AbfA belongs to glycoside hydrolase family (GH) 43 and removed arabinose from the C(O)2 and C(O)3 position of monosubstituted xylose residues. Furthermore, hydrolytic activity of AbfA was much larger towards substrates with a low amount of arabinose substitutions. AbfB from GH 51 only cleaved arabinoses on position C(O)3 of disubstituted xyloses, similar to GH 43 AXH-d3, making it to our knowledge, the first reported enzyme with this specificity in GH 51. AbfA acted synergistically with AbfB and AXH-d3. In combination with AXH-d3, it released 60% of arabinose from wheat AX. Together with recent studies on other AXOS degrading enzymes from B. adolescentis, these findings allowed us to postulate a mechanism for the uptake and hydrolysis of bifidogenic AXOS by this organism.
"The uptake and catabolism of XOS within bifidobacteria was recently proposed [37,60]. Comparative genomic of genes involved with XOS utilization within bifidobacteria (Figure 9) reflected a core gene structure of the XOS ABC transporter with a GH43 β-1,4-xylosidase (Balac_0517), while the occurrence of arabino-furanosidases, xylanases of GH8 and GH120 and carbohydrate esterases suggested more species and strain specific adaptation to utilize specific types of XOS e.g. "
[Show abstract][Hide abstract] ABSTRACT: Background
Probiotic bifidobacteria in combination with prebiotic carbohydrates have documented positive effects on human health regarding gastrointestinal disorders and improved immunity, however the selective routes of uptake remain unknown for most candidate prebiotics. The differential transcriptomes of Bifidobacterium animalis subsp. lactis Bl-04, induced by 11 potential prebiotic oligosaccharides were analyzed to identify the genetic loci involved in the uptake and catabolism of α- and β-linked hexoses, and β-xylosides.
The overall transcriptome was modulated dependent on the type of glycoside (galactosides, glucosides or xylosides) utilized. Carbohydrate transporters of the major facilitator superfamily (induced by gentiobiose and β-galacto-oligosaccharides (GOS)) and ATP-binding cassette (ABC) transporters (upregulated by cellobiose, GOS, isomaltose, maltotriose, melibiose, panose, raffinose, stachyose, xylobiose and β-xylo-oligosaccharides) were differentially upregulated, together with glycoside hydrolases from families 1, 2, 13, 36, 42, 43 and 77. Sequence analysis of the identified solute-binding proteins that determine the specificity of ABC transporters revealed similarities in the breadth and selectivity of prebiotic utilization by bifidobacteria.
This study identified the differential gene expression for utilization of potential prebiotics highlighting the extensive capabilities of Bifidobacterium lactis Bl-04 to utilize oligosaccharides. Results provide insights into the ability of this probiotic microbe to utilize indigestible carbohydrates in the human gastrointestinal tract.
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"resistant to enzymatic degradation in the intestinal lumen and therefore reach distal portions of the intestine. Different Bifidobacterium species are capable of metabolizing complex oligosaccharides usually from plant origin such as cellodextrins and amyloses (Pokusaeva et al., 2011), raffinose (Dinoto et al., 2006), arabinooligosaccharides (Lagaert et al., 2010; Van Laere et al., 1997), xylooligosaccharides (Gilad et al., 2010), fructooligosaccharides and inulin (Omori et al., 2010; Perrin et al., 2001; Rossi et al., 2005), galactans and galactooligosaccharides (GOS; (Barboza et al., 2009; Goulas et al., 2009a; Hinz et al., 2005; O'Connell Motherway et al., 2011)) among several others. "
[Show abstract][Hide abstract] ABSTRACT: Prebiotics are non-digestible substrates that stimulate the growth of beneficial microbial populations in the intestine, especially Bifidobacterium species. Among them, fructo- and galacto-oligosaccharides are commonly used in the food industry, especially as a supplement for infant formulas. Mechanistic details on the enrichment of bifidobacteria by these prebiotics are important to understand the effects of these dietary interventions. In this study the consumption of galactooligosaccharides was studied for 22 isolates of Bifidobacterium longum subsp. infantis, one of the most representative species in the infant gut microbiota. In general all isolates showed a vigorous growth on these oligosaccharides, but consumption of larger galactooligosaccharides was variable. Bifidobacterium infantis ATCC 15697 has five genes encoding β-galactosidases, and three of them were induced during bacterial growth on commercial galactooligosaccharides. Recombinant β-galactosidases from B. infantis ATCC 15697 displayed different preferences for β-galactosides such as 4' and 6'-galactobiose, and four β-galactosidases in this strain released monosaccharides from galactooligosaccharides. Finally, we determined the amounts of short chain fatty acids produced by strain ATCC 15697 after growth on different prebiotics. We observed that biomass and product yields of substrate were higher for lactose and galactooligosaccharides, but the amount of acids produced per cell was larger after growth on human milk oligosaccharides. These results provide a molecular basis for galactooligosaccharide consumption in B. infantis, and also represent evidence for physiological differences in the metabolism of prebiotics that might have a differential impact on the host.
[Show abstract][Hide abstract] ABSTRACT: I discuss the importance of capacitor matching in the context of
using charge stored on floating-gate MOS (FGMOS) transistors to
compensate for transistor mismatch in analog circuits. I describe a
simple technique that only involves static measurements for assessing
the relative mismatch between capacitors. I also show experimental
measurements of capacitor mismatch for small capacitors fabricated in
1.2-μm and 0.35-μm double-poly it n-well CMOS process that are
Circuits and Systems, 2000. Proceedings. ISCAS 2000 Geneva. The 2000 IEEE International Symposium on; 02/2000
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