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. Hydrolyzes birch-wood xylan, with a similar activity toward oat-spelt xylan. Also shows weak activities toward pNP-beta-D-cellobioside and pNP-beta-D-xylopyranoside, but no detectable activity toward carboxymethyl cellulose and pNP-beta-L-arabinofuranoside.-. Endohydrolysis of (1->4)-beta-D-xylosidic linkages in xylans. Optimum pH is 6.0. Optimum temperature is 70 degrees Celsius. Glycan degradation; xylan degradation. Belongs to the glycosyl hydrolase 10 (cellulase F) family.