DIGESTION OF STRUCTURAL POLYSACCHARIDES OF PANICUM AND VETCH HAYS BY THE RUMEN BACTERIAL STRAINS FIBROBACTER-SUCCINOGENES BL2 AND BUTYRIVIBRIO-FIBRISOLVENS D1

The rumen bacterial strains Fibrobacter succinogenes BL2 and Butyrivibrio fibrisolvens D1, were grown in monocultures and pair combination on cell walls (CW) of two tropical hays: Panicum (grass) and vetch (legume), and their ability to solubilize and utilize CW structural carbohydrate was determined. With respect to both substrates, F. succinogenes BL2 was a better solubilizer of CW carbohydrate than B. fibrisolvens D1. However, the solubilization of Panicum constituents by any bacterial monoculture and co-culture was higher than that of vetch. Complementary interaction between B. fibrisolvens D1 and F. succinogenes BL2 was identified only with respect to carbohydrate utilization, but not with the extent of CW solubilization, which was determined mainly by the F. succinogenes strain. In both substrates, utilization of solubilized cellulose by BL2 monocultures was high (86.4-97.5%), whereas that of solubilized xylan and hemicellulose was much lower (35.2-41.6%). Under scanning electron microscopy visualization, the BL2 bacterial cell mass attached to and colonized on CW particles was characterized by the appearance of protuberant structures known as ''polycellulosome complexes'' on their surface topology.