Endo-acting xylanase which specifically cleaves internal linkages on the xylan backbone, releasing xylooligosaccharides. Is able to hydrolyze oat spelt xylan and the arabinoxylans from wheat and rye, releasing xylobiose as the major product. Also likely catalyzes, via its C-terminal domain, the removal of acetyl groups from acetylated xylan. Thus, has the capability of hydrolyzing acetylated xylan. Does not attack mannan, galactan, arabinan or any cellulosic substrates. Endohydrolysis of (1->4)-beta-D-xylosidic linkages in xylans. Deacetylation of xylans and xylo-oligosaccharides. Glycan degradation; xylan degradation. Induced when the bacterium is cultured on xylan or beta-glucan but not on medium containing mannan. Is repressed by glucose. Transcription of xyn11A occurs in early exponential phase, and thus earlier than transcription of xyn11B. The N-terminal domain possesses xylanase activity, the central region likely has xylan deacetylase activity, and the small C-terminal domain is involved in carbohydrate-binding. In the N-terminal section; belongs to the glycosyl hydrolase 11 (cellulase G) family.