Effect of Konjac mannan on intestinal microbial metabolism in mice bearing human flora and in conventional F344 rats

Food Chem Toxicol. 1991 Sep;29(9):601-6. doi: 10.1016/0278-6915(91)90141-s.


The effects of dietary Konjac mannan (KM), a frequent ingredient of traditional Japanese foods, on intestinal microbial metabolism and microflora composition were investigated using two laboratory animal models, namely, conventional F344 rats and C3H/He male mice bearing human flora. Dietary KM led to a significant reduction in faecal beta-glucuronidase, nitroreductase and azoreductase activities, and in the production of phenol and indole in the faeces of conventional F344 rats. In the C3H/He male mice bearing human flora, faecal beta-glucuronidase and nitroreductase activities were significantly reduced by KM ingestion, as were the amounts of the putrefactive products, p-cresol and indole, in the faeces. Slight differences in intestinal microflora composition between control and KM diet groups were noted. The results indicate that, in C3H/He male mice bearing human flora, dietary KM may modify microbial metabolism without causing significant alterations in intestinal microflora composition.

MeSH terms

  • Animals
  • Bacteria / metabolism*
  • Dietary Fiber / pharmacology*
  • Feces / chemistry
  • Glucuronidase / analysis
  • Humans
  • Intestines / microbiology*
  • Male
  • Mannans / pharmacology*
  • Nitroreductases / analysis
  • Polysaccharides / pharmacology*
  • Rats
  • Rats, Inbred F344


  • Dietary Fiber
  • Mannans
  • Polysaccharides
  • (1-6)-alpha-glucomannan
  • Nitroreductases
  • Glucuronidase