Use of Xylose Dehydrogenase from Trichoderma viride in an Enzymic Method for the Measurement of Pentosan in Barley

A xylose dehydrogenase has been isolated from Trichoderma viride. It has been used as part of an enzyme-based assay to measure pentosan in barley. Pentosan is extracted with perchloric acid and then hydrolyzed by a cocktail of enzymes including xylanase, arabinofuranosidase, feruloyl esterase and acetyl esterase. Some 92% conversion to xylose was obtained, and this is measured in turn using a xylose dehydrogenase-based assay mixture involving NAD-dependent reduction of phenazine methosulphate monitored from absorbance increase at 585 nm. The xylose dehydrogenase is somewhat unstable and this will need to be enhanced for the assay to be functional.