Role of Intestinal Microbiota in Ulcerative Colitis
Role of Intestinal Microbiota in Ulcerative Colitis
Role of Intestinal Microbiota in Ulcerative Colitis
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Discussion and conclusion<br />
164<br />
7. Discussion and perspectives<br />
opportunistic pathogens; however <strong>in</strong> vivo studies or human trials are needed to confirm the ability<br />
<strong>of</strong> AOS to stimulate the growth <strong>of</strong> beneficial bacteria both <strong>in</strong> the lumen and mucus and through<br />
this able to promote health effects aga<strong>in</strong>st colitis.<br />
7.3. Validation <strong>of</strong> prebiotic properties <strong>of</strong> novel carbohydrates<br />
In Paper 4 and 5, novel carbohydrate preparations were tested <strong>in</strong> human fecal <strong>in</strong> vitro systems for<br />
prebiotic properties us<strong>in</strong>g FOS as prebiotic standard. The studies revealed that membrane<br />
separated AOS (DP7‐14) either feruloylated or nonferuloylated from sugar beet pect<strong>in</strong> (paper 4)<br />
and enzymatically produced β‐1,4‐galactan from potato pulp (paper 5) could stimulate the growth<br />
<strong>of</strong> bifidobacteria to the same extent or even higher than FOS after 24 hours <strong>of</strong> fermentation.<br />
In l<strong>in</strong>e with the results from Paper 4, bifidogenic effect <strong>of</strong> AOS (different cha<strong>in</strong> length, DP2‐10) has<br />
been described <strong>in</strong> vitro <strong>in</strong> previous communications (fecal samples from healthy subjects) (Al‐<br />
Tamimi et al., 2006;Hotchkiss et al., 2010) and Paper 3 (fecal samples from UC patients). It was<br />
expected that the feruloylated AOS from Paper 4 could selectively <strong>in</strong>crease the growth <strong>of</strong><br />
lactobacilli and bifidobacteria, because species <strong>of</strong> these genera have shown to be able to<br />
specifically express feruloyl esterase (Wang et al., 2005b;Szwajgier and Dmowska, 2010).<br />
However, the data revealed that the presence <strong>of</strong> feruloyl substitutions did not seem to be <strong>of</strong><br />
significant importance for the bifidogenic effect <strong>of</strong> AOS, but rather the molecular weight with high<br />
molecular weight AOS <strong>in</strong>duc<strong>in</strong>g growth <strong>of</strong> bifidobacteria.<br />
The results from Paper 5 demonstrated selective stimulation <strong>of</strong> bifidobacterial growth on high<br />
molecular weight β‐1,4‐galactan from potato pulp. Literature has previous described that pure<br />
culture species <strong>of</strong> Bacteroides, Bifidobacterium and Lactobacillus are able to utilize<br />
arab<strong>in</strong>ogalactan‐enriched polysaccharides (Van Laere et al., 2000) and <strong>in</strong> agreement with this,<br />
database search (http://www.cazy.org/, 2011‐10‐22) has revealed that species <strong>of</strong> Bacteroides,<br />
Bifidobacterium and Lactobacillus conta<strong>in</strong> β‐1,4‐galactanase (EC 3.2.1.89); an enzyme that<br />
catalyzes the degradation <strong>of</strong> β‐1,4‐galactan. This <strong>in</strong>dicates that even though several genera are<br />
able to utilize and grow on galactan, they may not be able to compete <strong>in</strong> mixed culture systems to<br />
the same extent as bifidobacteria.<br />
Paper 6 demonstrated that unsaturated oligogalacturonides (DP4 and DP5) from sugar beet HG<br />
were able to significantly alter the relative abundance <strong>of</strong> Firmicutes and Bacteroidetes us<strong>in</strong>g<br />
human fecal <strong>in</strong> vitro systems. Firmicutes and Bacterioidetes constitute the major part <strong>of</strong> the