Abstract
Many of the health benefits associated with dietary fiber are attributed to their fermentation by microbiota and production of short chain fatty acids (SCFA). The aim of this study was to investigate the fermentability of the functional fiber PolyGlyopleX® (PGX®) in vitro. A validated dynamic, computer-controlled in vitro system simulating the conditions in the proximal large intestine (TIM-2) was used. Sodium hydroxide (NaOH) consumption in the system was used as an indicator of fermentability and SCFA and branched chain fatty acids (BCFA) production was determined. NaOH consumption was significantly higher for Fructooligosaccharide (FOS) than PGX, which was higher than cellulose (p = 0.002). At 32, 48 and 72 h, acetate and butyrate production were higher for FOS and PGX versus cellulose. Propionate production was higher for PGX than cellulose at 32, 48, 56 and 72 h and higher than FOS at 72 h (p = 0.014). Total BCFA production was lower for FOS compared to cellulose, whereas production with PGX was lower than for cellulose at 72 h. In conclusion, PGX is fermented by the colonic microbiota which appeared to adapt to the substrate over time. The greater propionate production for PGX may explain part of the cholesterol-lowering properties of PGX seen in rodents and humans.
Highlights
Dietary fiber and resistant starches are substrates for bacterial fermentation in the human gastrointestinal tract that result in production of short chain fatty acids (SCFA), predominantly acetate, propionate and butyrate [1]
We have previously demonstrated that PGX® was associated with higher faecal total SCFA
This model has been validated with regards to the number and ratio of the various micro-organisms which are similar in composition and metabolic activity with that of the human colon as well as the production of metabolites, such as SCFA, branched short chain fatty acids (BCFA; iso-butyrate and iso-valerate), ammonia and phenolic compounds [5,6,7]
Summary
Dietary fiber and resistant starches are substrates for bacterial fermentation in the human gastrointestinal tract that result in production of short chain fatty acids (SCFA), predominantly acetate, propionate and butyrate [1]. The in vitro TIM-2 system is a multi-compartmental and dynamic laboratory system, which simulates to a high degree the colon, including a complex, high density, metabolically active, anaerobic microbiota of human origin. This model has been validated with regards to the number and ratio of the various micro-organisms which are similar in composition and metabolic activity with that of the human colon as well as the production of metabolites, such as SCFA, branched short chain fatty acids (BCFA; iso-butyrate and iso-valerate), ammonia and phenolic compounds [5,6,7]
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