The Digestion of Guar Gum by Individual Strains of Colonic Bacteria

Abstract

Experiments were carried out to determine the range of human colonic bacteria that could ferment the viscous polysaccharide, guar gum, and to seek evidence for collaboration between different strains of colonic bacteria. Single strains of a variety of species of bacteria isolated from human faeces were incubated with guar gum. Only seven of the 57 different strains of bacteria tested could alter the viscosity and pH of guar gum. These seven strains were all of the fragilis group of the genus Bacteroides, but were not confined to a particular species. Not all strains of the same species could ferment guar gum. One strain of B. variabilis and one strain of B. uniformis reduced the viscosity of untreated guar gum but did not affect the pH, suggesting that these strains may have degraded the gum by extracellular enzymes, but were unable to ferment the gum. Two strains (one B. distasonis, one B. thetaiotaomicron) fermented guar gum, only after it had been pretreated with a bacteria free filtrate of faeces that would contain extracellular enzymes. The results of this study suggest that different species of Bacteroides can interact in the digestion of viscous polysaccharides.

Key Words:

• Bacteroides
• Colonic
• Guar gum
• Extracellular enzymes