We have three soluble substrates for the measurement of xylanase activity. However we recommend using the Azo-Xylan (Birchwood) (S-AXBP or S-AXBL).  All of the Azo substrates are blue coloured and the reaction is determined by adding an alcohol solution followed by centrifugation.  In a petri dish assay, as the substrate is hydrolysed, it would diffuse more rapidly than the native substrate, giving zones of clearing.

Product Page (S-AXBP)

Product Page (S-AXBL)