Xylose-containing plant material may be hydrolyzed to xylose using a β-D-xylosidase which exhibits unexpectedly high activity. The enzyme has a kcat value for catalysis of approximately 185 sec−1 for 1,4-β-D-xylobiose (X2) when measured at a pH of 5.3 and a temperature of 25° C.; this is at least 10-fold greater than reported for other xylosidases at 25° C. and their optimal pH. The enzyme also has an isoelectric point of approximately 4.4. When reacted at a pH between about 4.5 and about 7.7, the β-D-xylosidase exhibits surprisingly high activity for hydrolyzing xylose-containing plant materials to xylose. The xylose released from plant materials may then be converted to other secondary products such as ethanol by fermentation or other reaction. This β-D-xylosidase may be used alone or in combination with other hydrolytic or xylanolytic enzymes for treatment of lignocellulosic or hemicellulosic plant materials or plant material hydrolysates or xylooligosaccharides.