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Background: Only recently the concept of prebiotics has been introduced in oral health. Few potential oral prebiotics have already been identified in dual species competition assays, showing a stimulatory effect on beneficial bacteria and by this suppressing the outgrowth of pathogenic species. This study aimed to validate the effect of previously identified potential prebiotic substrates on multispecies cultures by shifting the biofilm composition towards a more beneficial species dominated microbiota. Methods: A chemostat culture containing 14 model oral bacterial species was used to grow biofilms for 24 hours which subsequently were treated with prebiotic solutions three times a day for 3 consecutive days. Further the influence of environmental factors such as pH, nutrient availability, oxygen concentration and prebiotic dose on the efficacy of the prebiotic substances was investigated. Results: Three potential prebiotic substrates N-acetyl-D-mannosamine, succinic acid and Met-Pro were able to bring the beneficial proportion to > 95%. While the pH of the prebiotic solution did not have an influence on the prebiotic effect, the interplay of nutrient availability, oxygen concentration and prebiotic treatment resulted in significant changes of the microbial composition identifying N-acetyl-D-mannosamine as the most promising oral prebiotic substrate. Showing a clear dose dependent effect, concentrations of N-acetyl-D-mannosamine of 1.0 and 1.5 M resulted in a biofilm composition of 97% beneficial species. Conclusion: Introducing the prebiotic concept in oral health might reveal a valid approach for treatment and prevention of oral diseases and promote oral health.

The aim of this research was to study the in vitro fermentation of chicory root pulp (CRP) and ensiled CRP (ECRP) using human fecal inoculum. Analysis of carbohydrate levels in fermentation digests showed that 51% of all CRP carbohydrates were utilized after 24 h of fermentation. For ECRP, having the same cell wall polysaccharide composition as CRP, but with solubilization of 4 times more of CRP pectin due to ensiling, the fermentation was quicker than with CRP as 11% more carbohydrates were utilized within the first 12 h. The level of fiber utilization for ECRP after 24 h was increased by 8% compared to CRP. This effect on fiber utilization from ECRP seemed to arise from (i) increased levels of soluble pectin fibers (arabinan, homogalacturonan, and galactan) and (ii) ahypothesized more open structure of the remaining cell walls in ECRP, which was more accessible to degradation than the CRP cell wall network. KEYWORDS: chicory root pulp, ensiled chicory root pulp, insoluble

Modulation of the human gut microbiota has proven to have beneficial effects on host health. The aim of this work was to evaluate the effect of sun-dried raisins (SR) on the composition of the human gut microbiota. A full model of the gastrointestinal tract, which includes simulated mastication, a dynamic gastric model, a duodenal model and a colonic model of the human large intestine, was used. An increase in the numbers of bifidobacteria and lactobacilli was observed by plate-counting in response to the addition of either SR or FOS after 8 and 24 h fermentation. A significant decrease in Firmicutes and Bacteroidetes was observed in SR samples after 8 and 24 h fermentation. FOS resulted in the greatest production of short chain fatty acids. Sun-dried raisins demonstrated considerable potential to promote the colonization and proliferation of beneficial bacteria in the human large intestine and to stimulate the production of organic acids.

Emerging evidence suggests that the gut microbiota has a critical role in both the maintenance of human health and the pathogenesis of many diseases. Modifying the colonic microbiota using functional foods has attracted significant research effort and product development. The pioneering concept of prebiotics, as introduced by Gibson and Roberfroid in the 1990s, emphasized the importance of diet in the modulation of the gut microbiota and its relationships to human health. Increasing knowledge of the intestinal microbiota now suggests a more comprehensive definition. This paper briefly reviews the basics of the prebiotic concept with a discussion of recent attempts to refine the concept to open the door for novel prebiotic food ingredients, such as polyphenols, minerals and vitamins.

Oligosaccharides produced by hydrothermal processing of rice husks (xylooligosaccharides and glucooligosaccharides) were refined by membrane processing (operating in diafiltration and concentration modes), subjected to xylanase treatment to reduce the average molar mass, and subjected to further purification by ultrafiltration (operating in concentration mode) and ion exchange. The purified products were assayed for composition, molar mass distribution and structural characterization by HPLC, HPAEC-PAD, HPSEC, MALDI-TOF-MS and NMR ((1)H and (13)C). The fermentability of the purified product by fecal inocula was assessed on the basis of the time courses of pH and oligosaccharide concentrations. Succinate, lactate, formiate, acetate, propionate and butyrate were the major products resulting from fermentation experiments.