Endo-acting xylanase which specifically cleaves internal linkages on the xylan backbone, releasing xylooligosaccharides. Is able to hydrolyze glucuronoxylan and the arabinoxylan from wheat. Endohydrolysis of (1->4)-beta-D-xylosidic linkages in xylans. 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 xyn11B occurs later than transcription of xyn11A. Is expressed at maximum level in mid-log phase, and its transcription persists into the late exponential and early stationary phases. Belongs to the glycosyl hydrolase 11 (cellulase G) family.