Product Overview :
For the measurement and analysis of endo-1,4-β-D-xylanase in enzyme preparations, bread improver mixtures and animal feeds. Contains Xylazyme AX Tablets and xylanase enzyme controls (A. niger and Trichoderma longibrachiatum).
Scientific Background :
Arabinoxylan is the major endosperm cell-wall polysaccharide of wheat and rye and is found in significant proportions in most cereal solutions and slurries of high viscosity and, in animal nutrition, it reduces the rate of nutrient absorption from the gut. endo-β-D-Xylanase (xylanase) is added to feeds to catalyse depolymerisation of this polysaccharide. It can be demonstrated that endo-cleavage by xylanase of just one bond per thousand in the arabinoxylan backbone can significantly remove viscosity properties.
Of the carbohydrase enzymes used as feed supplements, one of the most difficult to measure has been xylanase. These problems are attributed to several factors, including the low levels of enzyme added to the feed, inactivation of enzyme during pelleting, binding of the enzyme to feed components and the presence of specific xylanase inhibitors.
The only biochemical methods which are sufficiently sensitive, specific and robust to measure xylanase in feeds are viscometric assays and those employing dyed xylan or arabinoxylan polysaccharides.Viscometric assays are tedious, whereas assays employing dyed xylan substrates are rapid, reproducible and simple to perform. We recommend the use of either Xylazyme AX tablets or Azo-Wheat Arabinoxylan (Azo-WAX). Xylazyme AX based assays are about 5-fold more sensitive than assays employing Azo-WAX. However, this latter substrate does have sufficient sensitivity in most applications, and results are slightly more reproducible than with Xylazyme AX.
It is generally accepted that xylanase enzymes which are best suited to feed applications have optimal activity at pH 6.0. Consequently, these enzymes are generally assayed at this pH in 100 mM sodium phosphate buffer. In recovery experiments, however, we found that sodium phosphate buffer extracts only a small proportion (< 20%) of the amount of enzyme added to the feed. Thus a wide range of alternative extractants and extraction conditions have been evaluated. For feeds containing Trichoderma sp. xylanases, the best and most consistent results have been obtained using 100 mM acetic acid or 100 mM sodium acetate buffer (pH 4.7) at room temperature. Optimal extraction of Humicola sp. xylanases was achieved with a buffer containing 100 mM MES buffer (pH 6.0) and 1% w/v sodium dodecyl sulphate (SDS).
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