A β-d-xylosidase from the thermophileCaldocellum saccharolyticumexpressed inEscherichia coli

The gene coding for a β-d-xylosidase (E.C. 3.2.1.37) of the thermophile Caldocellum saccharolyticum was isolated previously as part of a gene cluster which has been cloned in Escherichia coli. The enzyme characteristics were determined in E. coli using toluenized cell extracts. The pH optimum was 6.5 and temperature optimum 70°C. The enzyme was stable at 60°C and the half life at 80°C was 45 minutes. The temperature optimum and the temperature stability exceed those reported for other bacterial or fungal β-d-xylosidases. The enzyme showed no other detectable xylanolytic or cellulolytic enzyme activity.