Wheat straw hemicelluloses: composition and fermentation by human colon Bacteroides

The hemicellulosic components of wheat straw have been partially characterized, and the ability of selected anaerobic bacteria from the human colon to ferment wheat straw, its hemicellulose fractions, and commercial xylan was evaluated. Three strains of Bacteroides ovatus , which grew particularly well on media containing hemicellulose, were examined for the presence and cellular localization of the hemicellulose-degrading enzymes. Wheat straw contained about 75% carbohydrate on a dry weight basis. Xylose was the major sugar in the hemicelluloses, representing about 31% of crude hemicellulose and 50% of hemicelluloses A and B. Of the 12 strains of Bacteroides sp. tested, none fermented wheat straw. Of seven strains of B. ovatus evaluated, six fermented crude hemicellulose and hemicelluloses A and B. Of five strains representing Bacteroides vulgatus, Bacteroides uniformis , and Bacteroides thetaiotaomicron , none fermented hemicelluloses. The hemicellulose-degrading enzyme activity was predominantly intracellular.