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Methanol production from the degradation of pectin by human colonic bacteria
R J Siragusa1, J J Cerda, M M Baig
1Department of Medicine, Unviersity of Florida College of Medicine, Gainesville.
Abstract:
When ingested, pectin can lower serum cholesterol levels in humans. Pectin is degraded by fecal bacteria in the colon. We examined the release of methanol (MeOH) by this degradation. A 0.2% glucose (2 g/L) mixture was used as the control medium. A pure culture of pectinolytic Erwinia carotovora was the control bacterium. The chief substrates were, in set 1, 0.2% pectin (2 g/L) and, in set 2, 0.1% glucose (1 g/L) and 0.1% pectin (1 g/L). Cultures of fecal bacteria and E carotovora grew for 72 h in each of the solutions. By 72 h the fecal flora culture in set 1 cleaved 30% of the possible methoxyl groups on pectin. The fecal flora in set 2 cleaved 90.7% of all possible methoxyl groups. Balance studies suggest that all of the free MeOH comes from methoxyl groups on pectin. This study demonstrates that fecal bacteria are capable of degrading pectin to release MeOH.
Insights
Fecal bacteria degrade pectin in the colon, releasing methanol. This study shows that gut bacteria can break down pectin, a fiber known to lower cholesterol, and produce methanol as a byproduct.
Area of Science:
- Microbiology
- Biochemistry
- Human Nutrition
Background:
- Pectin, a dietary fiber, is known to reduce serum cholesterol levels in humans.
- The colon's fecal bacteria degrade pectin.
- The metabolic byproducts of pectin degradation by gut microbiota are not fully understood.
Purpose of the Study:
- To investigate the release of methanol (MeOH) during pectin degradation by fecal bacteria.
- To quantify methanol production from pectin by human fecal microbiota in vitro.
- To determine the source of methanol generated from pectin breakdown.
Main Methods:
- In vitro cultures of human fecal bacteria and pure cultures of Erwinia carotovora were used.
- Experiments involved control media with glucose and experimental media with pectin or pectin and glucose.
- Pectin degradation and methoxyl group cleavage were monitored over 72 hours.
Main Results:
- Fecal flora cultures degraded 30% of pectin's methoxyl groups in pectin-only media.
- In mixed media (pectin and glucose), fecal flora cleaved 90.7% of available methoxyl groups.
- Balance studies indicated that all released methanol originated from pectin's methoxyl groups.
Conclusions:
- Human fecal bacteria effectively degrade pectin, releasing methanol.
- The extent of pectin degradation and methanol release is influenced by the presence of other substrates like glucose.
- This study confirms that fecal bacteria are a source of methanol production from dietary pectin.