1. General Background 2. The substrate: Xylan 3. Microbial xylanolytic systems and their properties 4. Structure and Synergism between the enzymes of the Xylanolytic complex 5. Sources, production, and classification of xylanases 6. Enhanced xylanase production by using statistical designs 7. Molecular cloning and expression of xylanase gene 8. Strain improvement by mutation 9. Purification and characterization of xylanases 10. Immobilization of xylanases 11. Industrial applications of xylanases 12. Challenges and future trends in commercial production and application of xylanases