Endo-1,4-beta-xylanase involved in the hydrolysis of xylan, a major structural heterogeneous polysaccharide found in plant biomass representing the second most abundant polysaccharide in the biosphere, after cellulose. Shows an endo-mode of action on xylan forming mainly xylobiose and short-chain xylooligosaccharides (XOS). Endohydrolysis of (1->4)-beta-D-xylosidic linkages in xylans. Inhibited by wheat xylanase inhibiting protein I (XIP-I). Optimum pH is 4.2-5.2 for birchwood xylan and 4.0 for CM cellulose. Glycan degradation; xylan degradation. Belongs to the glycosyl hydrolase 10 (cellulase F) family.