The invention relates to an isolated and purified culture of Bacillus sp. strain 720/1 (LMG P-14798); to xylanases obtained from this strain and xylanases obtained from derivatives and mutants of strain 720/1. The invention also relates to a DNA molecule encoding a xylanase and to expression vectors or integration vectors containing the DNA molecule. This invention also relates to transformed host strains comprising the DNA molecule encoding the xylanase.