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

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-β-D- mannopyranosyl-D-mannopyranose (β-1,4-D-mannobiose), 4-O-β-D- glucopyranosyl-D-glucopyranose (cellobiose), 4-O-β-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.