Fig. 4

Xylanase activity after incubation with enzymatic hydrolysis residue (EnzHR) lignin. Distribution of xylanase activities for xylanases a TrXyn1, b TrXyn2,c Xyl40 and d Xyl40-CD is presented as a percentage of the initially measured activity using the standard assay conditions (50 °C). Xylanase was incubated in 50 mM Na-citrate buffer, pH 5 at 40 °C in the presence of EnzHR lignin isolated from steam pretreated spruce (Lignin) or without lignin (Control). After incubation for 3 or 24 h the solution was centrifuged and the supernatant (Free enzyme) was separated from the solid lignin containing lignin-bound enzymes. The loosely bound enzymes were washed from the lignin with buffer (loosely bound enzyme) and after centrifugation the pellet containing solid lignin was resuspended into buffer for the activity assay (lignin-bound enzyme)