Degradation of konjac glucomannan by enzymes in human feces and formation of short-chain fatty acids by intestinal anaerobic bacteria

J Nutr Sci Vitaminol (Tokyo). 1998 Jun;44(3):423-36. doi: 10.3177/jnsv.44.423.

Abstract

Konjac (konnyaku) glucomannan was examined for its degradation in human intestines and fermentation products. The konjac glucomannan was degraded almost 100% by soluble enzymes in human feces to give 4-O-beta-D-mannopyranosyl-D-mannopyranose (beta-1,4-D-mannobiose), 4-O-beta-D-glucopyranosyl-D-glucopyranose (cellobiose), 4-O-beta-D-glucopyranosyl-D-mannopyranose, and small amounts of glucose and mannose. These three disaccharides were further degraded by a cell-associated enzyme(s) to glucose or mannose, or to both. Konjac glucomannan underwent fermentation by intestinal anaerobic bacteria and produced formic acid, acetic acid, propionic acid, and 1-butyric acid. These fatty acids were different in their proportions among test subjects, their total amounts ranging from 17.1% to 48.8% of the initial konjac glucomannan.

MeSH terms

  • Acetic Acid / metabolism
  • Adult
  • Bacteria, Anaerobic / metabolism*
  • Butyric Acid / metabolism
  • Cellobiose / metabolism
  • Dietary Fiber
  • Fatty Acids / biosynthesis*
  • Feces / enzymology*
  • Female
  • Fermentation
  • Food
  • Formates / metabolism
  • Glucose / metabolism
  • Humans
  • Intestines / microbiology*
  • Male
  • Mannans / metabolism*
  • Mannose / metabolism
  • Middle Aged
  • Propionates / metabolism

Substances

  • Dietary Fiber
  • Fatty Acids
  • Formates
  • Mannans
  • Propionates
  • formic acid
  • Butyric Acid
  • mannobiose
  • Cellobiose
  • (1-6)-alpha-glucomannan
  • Glucose
  • propionic acid
  • Mannose
  • Acetic Acid