Submitted to: Applied and Environmental Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: December 14, 1995
Publication Date: N/A
Technical Abstract: Ruminal bacteria rapidly degrade xylan and the initial enzymatic hydrolysis is generally more rapid than subsequent fermentation. As a result, a pool of partially digested intermediate products accumulates in cultures and is composed, at least in part, of xylooligosaccharides. Oligosaccharide accumulation during the degradation of starch and cellulose has been proposed as a mechanism by which crossfeeding between polysaccharide degrading and soluble sugar utilizing species is thought to occur. The potential for this type of crossfeeding relationship was studied by cocultivating the xylanolytic bacterium Butyrivibrio fibrisolvens H17c with the xylooligosaccharide fermenting bacterium Selenomonas ruminantium GA192. Stable xylan, utilizing cocultures of S. ruminantium and B. fibrisolvens, were established by inoculation of both organisms into a complex, Trypticase-yeast extract-containing medium containing 0.2% oat spelt and were maintained by transfer twice a week into fresh medium. In contrast to the findings of some studies, xylan utilization was not enhanced in cocultures of B. fibrisolvens and S. ruminantium. Despite the presence of an oligosaccharide fermenting organism, accumulations of soluble products were still noted; however, the composition of carbohydrates present in these cultures differed from that when B. fibrisolvens was cultivated alone. Structural characterization of these residual products may help define the limitations on the assimilation xylooligosaccharides by ruminal bacteria.