Poster Topical Area: Nutritional Microbiology
Poster Board Number: 235
Objectives: Dietary polyphenols have poor bioavailability in the upper gastrointestinal tract; benefits are primarily due to metabolites produced during microbial fermentation in the colon. Our work employs in vitro fermentation as a means to explore the systematic processes of colonic bacterial metabolism of dietary inputs. The broad experimental capacity of in vitro fermentation enables generation of multi-faceted data sets (time- and dose-dependent, colonic domain specific, etc.) to gain understanding of bacterial community dynamics. Here, we present our efforts regarding cranberry A-type proanthocyanidins (PAC) and its impact on the in vitro gut microbial community.
Methods: Static batch fermentations were performed in triplicate, utilizing fecal inocula derived from three individuals, in a nutrient-rich anaerobic media supplemented with purified cranberry PAC at low and high doses. Aliquots sampled at 0 and 24 hours were analyzed for bacterial growth (protein content of lysed cells), bacterial identification (16s rRNA sequencing), short-chain fatty acid content (GC-FID) and phenolic metabolite content (GC/MS).
Results: Total growth assessment revealed a linear increase in growth as a function of PAC dose. Bacterial population dynamics indicated a dose-dependent increase in several beneficial taxa, including Ruminococcus spp. (p < 0.05), some of which are associated with resistant starch degradation in the colon. Phenolic metabolite generation dependent on PAC dosage was demonstrated; several identified compounds, such as 3-(4-OH-phenyl) propionic acid (p < 0.001), are associated with anti-inflammatory activity in literature. A PAC-dependent increase in beneficial butyrate production was also observed. PAC-dependent growth under conditions simulating the multiple domains of the colon revealed domain-dependent growth behavior; domain-specific bacterial population and metabolite assessments are ongoing.
Conclusions: The results suggest cranberry PAC may have a prebiotic effect on gut microbiota in vitro, particularly at a high dose. Efforts toward understanding the gut microbiota metabolism of PAC could impact future dietary supplementation approaches, supporting Army efforts to build Soldier resiliency to military-relevant stressors through nutritional strategies.
Research Chemical Engineer
US Army Natick Soldier Research Development & Engineering Center