Alternative pathways for hydrogen disposal during fermentation in the human colon

Area of Science:

• Microbiology
• Gastroenterology
• Human Physiology

Background:

• Hydrogen gas is a fermentation byproduct in the human colon.
• Gut bacteria utilize hydrogen via methanogenesis, sulphate reduction, or acetogenesis.

Purpose of the Study:

• To determine the predominant hydrogen disposal pathways in the large intestine.
• To investigate factors influencing these metabolic routes.

Main Methods:

• Stool samples from 30 healthy subjects were incubated.
• Incubation involved 5% (w/v) slurries with Lintner's starch.
• Hydrogen metabolism pathways (methanogenesis, sulphate reduction, acetogenesis) were measured.

Main Results:

• Methane production predominated in 23 of 30 subjects.
• Sulphate reduction and H2S production were significant in the remaining seven.
• Both pathways were influenced by pH; sulphate reduction favored alkaline, methanogenesis neutral, and acetogenesis acidic conditions.

Conclusions:

• Competing pathways for hydrogen disposal exist in the colon.
• Sulphate availability and colonic pH are key factors determining the dominant pathway.
• Methanogenesis and sulphate reduction appear mutually exclusive in the colon.