Alternaria sp. ND-16, a bacterium isolated from soil sample, was identified as a strain of Alternaria mali based on the morphology and comparison of internal transcribed spacer rDNA gene sequence studies. Furthermore, it is demonstrated that this strain has xylanase activity, and the activity can be optimized under suitable growing conditions where wheat bran and urea are the primary sources of carbon and nitrogen. Partially purified xylanase from Alternaria sp. ND-16 is shown to have an optimal pH of 6.0 and optimal temperature of 50 A degrees C, making this enzyme potentially suitable for industrial applications. It is also demonstrated that Na+ and Mn2+ show strong inhibition of the xylanase while K+, Li+, Fe2+, Cu2+, and Zn2+ have no significant effect on the activity.