According to our previous study, Hom-Kaek (Allium cepa var. viviparum) was found to
consist of fructooligosaccharides which have been approved to be one of potential prebiotics. This
extract, the so-called inulin-fructooligosaccharides ( inulin-FOSs) , is in form of syrup. To be a
prebiotic substance, one must be resistant to a host digestive system system and must be
specifically fermentable by intestinal microbial community and thus promoting host health. In
vitro digestive gut models have been widely accepted for the evaluation of structural changes,
digestibility and fermentability of certain prebiotics. In the past, plate count is a method for
determination of fermentability of prebiotics fermented by a natural inoculum. However, this
method is limited to measure the number and type of some microorganisms and to
comprehensively indicate microbial diversity. The aim of this research study was to evaluate
digestibility and fermentability of inulin-FOSs from Hom-Kaek in the human gut model. The
inulin-FOSs were standardized by quantitative analysis of total sugar and reducing sugars using
phenol-sulfuric acid and DNS methods, respectively and qualitative analysis by thin layer
chromatography (TLC). The standardized inulin-FOSs consisted of 98.0?2.8 g/L total sugars and
8.7?0.62 g/L reducing sugar, thus calculating to degree of polymerization of 11. The obtained
inulin-FOSs contained glucose and fructose as the contaminated monosaccharides and sucrose as
the contaminated disaccharide. The digestibility evaluation results revealed that inulin-FOSs were
resistant toward the simulated oral, gastric, and intestinal conditions after evaluating the released
reducing sugars and profile of inulin-FOSs by thin-layer chromatography obtained from the in
vitro gastrointestinal system. The tested probiotic lactobacilli could specifically fermented inulin-
FOSs and had the same growth pattern as those fermented in glucose, fructose, and sucrose.
Fermentation of the inulin-FOSs in human gut model was conducted using fecal slurry from
healthy infant as the representative of natural inoculum. The next generation sequencing (NGS)
technique was used to determine bacterial diversity and population. The results found that the
most abundance bacteria which were selectively simulated by the inulin-FOSs belonged to
phylum Actinobacteria such as Bifidobacterium sp. Their numbers were increased proportionallyto fermentation time. Meanwhile, bacterial members in phylum Firmicutes such as Clostridium
sp. and Proteobacteria including e. g. Veillonella sp. , Entercoccus sp. , Klebsiella sp. and
Escherichia-Shigella, were the second most abundance bacteria. They were decreased with regard
to the increased numbers of Actinobacteria in particular Bifidobacterium breve and Bb. bifidum.
The results were in agreement with main short-chain fatty acids (SCFA) produced from inulin-
FOSs fermentation including lactic acid and acetic acid. These SCFA are in fact produced by
Bifidobacterium sp. Moreover, the results revealed that the major fermentative carbon sources
were the contaminated glucose, fructose and sucrose, the retained residues after the purification of
inulin-FOSs, two different FOSs including kestose and an unidentified saccharide with a polarity
that is closely related to kestose as judged by TLC technique. Overall, it can be concluded that
inulin-FOSs from Hom-Kaek possesses prebiotic properties and can exhibit its function alone
without probiotic microorganisms. With regard to the changes in bacterial population during the
fermentation, it can be implied that the inulin-FOSs from Hom-Kaek can promote host health.