Xylan neutral type

The specificity of a xylanase preparation may be determined from the isolation and characterization of oligosaccharides formed from xylan hydrolysis. While the oligosaccharides released were mainly dependent on the specificity of the xylanase, the complex structure of the heteroxylan also determines the extent of hydrolysis and the site of cleavage. Two types of xylooligosaccharides are usually produced acidic (from glucuronoxylans) and neutral (from arabino- and arabinoglucurono-xylans). The specificity of the action of several purified xylanases on various heteroxylans is shown below ... 

The recent studies of the Finnish group further emphasize the complexity of the xylan in wood cellulose. These workers have shown that the properties of the xylan in wood pulps depend not only on the method of pulping but also on the type of raw material. It was observed that, when pulps are prepared by the (acidic) sulfite process from the softwoods, pine and spruce, a substantial part of the xylan is of the acidic type (see Fig. 2, p. 303). Even when these sulfite pulps are refined further with hot alkali, some acidic xylan remains. However, when pulps are prepared from pine and spruce by the (alkaline) sulfate process, the acidic xylan is removed and only neutral xylan remains. 

A Bacillus species from soil was able to synthesize a xylanase in alkaline, but not neutral, media. After purification by ion-exchange chromatography and gel filtration, the xylanase (3.55, p/ 6.3) exhibited activity in the pH range 5.5—9.0 and was most stable at pH 7. Since the enzyme hydrolysed xylan to xylobiose and higher oligosaccharides, it is a type of e/i fo-xylanase. The xylanase was inhibited by Ag+, Cd +, and Hg + ions. 

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