Role of xylan degrading enzymes in fiber digestion in ruminants

Xylan, as a main component of hemicellulose, is one of the most abundant polysaccharides consumed by the ruminant, and the extent and rate of xylan digestion may exert a major influence on the amounts of nutrients supplied to ruminant animals. Xylan in nature exists as complex compounds with a xylopyranose unit being substituted with acetic acid, 4-O-methylgluaronic acid and arabinose, or being esterified by phenolic acids. Therefore, several enzymes are involved in the complete digestion of xylan. Rather extensive researches have been carried out on enzymatic and genetic characterization of non-rumen microbial xylanases, but limited information is available for rumen microbial xylanases. Recent developments in enzymology and molecular biology of xylanase and related enzymes of rumen microorganism are described in this paper. The synergistic nature of xylan degrading enzymes in terms of fiber digestion is discussed.