The thermostability of absolutely purified xylanase from Aspergillus niger DFR-5 was improved using polyols. Supplementation of sorbitol at 2M concentration was found to increase the half-life and D-value of xylanase at elevated temperatures (45-70ºC). Thermodynamic parameters associated with the process were analyzed revealing that the stability at higher temperatures was due to the increased enthalpy (âˆ†Hº) and free energy (âˆ†Gº) change of enzyme denaturation in the presence of sorbitol. The negative values of âˆ†Sº (-150.093 Jmol-1K-1 at 70ºC) clearly indicated that enzyme underwent a significant process of aggregation during denaturation. The enzyme required divalent cations for maximum activity and inhibited by chelator. The diminution of activity by various thiol-binding agents and enhancement by reducing agents like β-ME confirmed the essentiality of cysteine for catalysis. The enzyme had a half-life and D-value of 277 and 921 days when stored at 4 ºC.