(P27-010-24) Circumventing Interindividual Variability: Dietary Fibers of High Specificity Allow Predictable Shifts in the Gut Microbiota

Objectives: Most dietary fibers currently used as prebiotics show different and therefore unpredictable responses in individuals harboring distinct microbial communities. We previously proposed that fibers of higher structural specificity (i.e., used by a narrow group of gut bacteria) could have more similar responses across subjects than low specificity ones (i.e., used by many gut bacteria). We aimed to test this hypothesis using gut microbial communities from different individuals as well as to understand how structural variations affect microbiota outcomes of high specificity fibers.

Methods: We conducted in vitro fecal fermentations of fibers of low (fructooligosaccharides, FOS; and resistant starch, RS), medium (pectin), and high specificity fibers (an insoluble β-1,3-glucan), using fecal inoculum from 10 distinct individuals. we fermented different structural variants of the high specificity β-1,3-glucan (soluble, insoluble, and debranched forms) with pooled fecal inocula to assess the impact of structural alignment on targeting gut bacteria. Assessed outcomes included short-chain fatty acids (SCFAs) and bacterial composition (accessed by 16S rDNA sequencing) before and after fermentations.

Results: β-diversity analysis showed that divergent fiber responses occur in distinct microbial communities when utilizing the low specificity fibers (FOS and RS), but fibers of higher specificity (pectin and β-1,3-glucan) led to more similar responses. In fact, the highly specific β-1,3-glucan targeted Anaerostipes sp. and Bacteroides uniformis, promoting a strong growth (from 0.3 to 16.5% and 2.5 to 17.9%, respectively) in every microbial community that had these bacteria originally present. These were accompanied by marked increases in the SCFAs butyrate and propionate, which are known to be beneficial to human health. Finally, we have shown that shifts in the β-1,3-glucan's solubility and branching pattern completely modify Anaerostipes response, emphasizing the importance of fiber fine structure-bacteria alignment.

Conclusions: We have shown that high specificity dietary fibers aligned in structure to target specific bacteria have potential to promote homogeneous and predictable responses across people and are promising as the next generation prebiotics with high efficacy.

Funding Sources: USAMRMC/DoD; CNPq Foundation (Brazil)