The major polysaccharide component from the stalk of Allium schoenoprasum (AssP) was extracted and purified. Gel filtration chromatography purified AssP exhibited a molecular weight of around 1.7 kDa, which was verified by MALDI-ToF-MS. The monosaccharide analysis revealed its composition as rhamnose: arabinose: galactose: glucose: mannose: fructose with a molar ratio of 0.03:2.46:3.71:3.35:1.00:9.93, respectively. The Congo-red assay indicated that there was no tertiary structure of this polysaccharide, however, it self-assembled into a homogenous nanoparticle with a diameter of ~600 nm as revealed by the dynamic light scattering measurement. The solution behavior of this polysaccharide was simulated. The association of this polysaccharide was both time dependent and concentration dependent. AssP forms spherical particles spontaneously as time passes by, and when the AssP concentration increased, the spherical particles increased their sizes and eventually merged into cylindrical micelles. The diversity of AssP hydrodynamic behavior endowed potential versatility in its future applications.

Precision modulation of gut microbiota requires elucidation of the relation between dietary fiber intake and gut microbe dynamics. However, current studies on this aspect are few due to many technical limitations. Here, we used Caenorhabditis elegans to minimize the complicated host–microbial factors and to find the relation between dietary fiber chemical structures and gut microbiota dynamics. The Allium schoenoprasum polysaccharide (AssP) structure was elucidated and used as the complex dietary fiber against the simple fiber inulin. In vitro bacterial growth and genome analysis indicated that AssP supports bacterial growth better than inulin, while in vivo gut microbiota analysis of C. elegans fed with AssP showed that microbiota richness increased significantly compared with those fed with inulin. It is concluded that the more complex the dietary fiber chemical structure, the more gut bacteria growth it supports. Together with the community bacterial interactions that alter their abundances in vivo, these factors regulate gut microbiota synergistically.

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Abstract Background: Allium schoenoprasum is a world-wide common vegetable while only its leave is used in the food factory. Its stalk is largely discarded, for potential heavy metal accumulations, which eventually lead to an environmental contamination. To fully utilize this vegetable and minimize its metal content, the major polysaccharide content is purified and characterized with chemical and computational approaches.Results: The major polysaccharide component from the stalk of Allium schoenoprasum (AssP) was extracted and purified. The gel filtration chromatography purified AssP exhibited a molecular weight of around 1.6 kDa, which was verified by MALDI-ToF-MS. Monosaccharide analysis revealed its composition as rhamnose: arabinose: galactose: glucose: mannose: fructose with a molar ratio of 0.0264:2.46:3.71:3.35:1.00:9.93, respectively. Multiple NMR analysis revealed its backbone as α-Ara/Glu/Gal-(1→2)-linked and β-D-Fru-(4→5)-linked sugar residues. There was no tertiary structure of this polysaccharide, however, it self-assembled into a homogenous nanoparticle with a diameter of ~600 nm. The solution behavior of this AssP polysaccharide was simulated, and there was no specific binding site on one molecule for another. Association of this polysaccharide was concentration dependent. As the AssP concentration increased, the spherical particles increased their sizes and eventually merged into cylindrical micelles. The diversity of AssP hydrodynamic behavior endowed potential versatility in its applications.Conclusions: AssP was characterized as a polysaccharide with identified monosaccharide compositions and linkage between them. Although there is no tertiary structure in one AssP molecule, self-assembly of AssP molecules could form nanoparticles or micelles depending on its solution concentrations. The unique AssP solution behavior endows itself a potential biomaterial for nanoparticles preparations.