Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: May 21, 1998
Publication Date: N/A
Technical Abstract: Xylans are abundant polysaccharides in plant cell walls and make up a large portion of many agricultural residues. The microbial degradation of xylans is often incomplete possibly due to the complex structure of these polysaccharides. This is particularly true for corn fiber xylan (CFX) where the xylose backbone is highly substituted with arabinose, xylose, galactose, and glucuronic acid residues. An anaerobic bacterium capable of rapid growth on corn fiber xylan was isolated from rumen enrichment cultures. This strain, RZ, is a strictly anaerobic, Gm- pleomorphic rod-shaped bacterium phenotypically similar to Prevotella ruminicola, but only possesses 87% 16s rRNA gene sequence identity with the type strain of P. ruminicola. In addition to CFX, strain RZ also utilized xylans isolated from a variety of plant sources. Xylosidase, arabinosidase, and xylanase activities were produced by strain RZ. Xylosidase and arabinosidase activities appear to be synthesized constitutively, while there was a fivefold increase in the level of xylanase produced when strain RZ was grown on xylan rather than simple sugars. The use of CFX by strain RZ was compared to that by other ruminal xylanolytic bacteria. Strain RZ grew rapidly on CFX and utilized greater than 90% of the substrate (2.5 mg/ml) in less than 8 h. In contrast, all other ruminal bacteria exhibited poor growth on CFX. Strain RZ grew more rapidly on many substrates than the other strains, but this alone cannot explain the superior ability of this strain to grow on CFX.