An artificial bifunctional enzyme, xylanase-cellulase, has been prepared by gene fusion. Three chimeric genes were constructed that encoded fusion proteins of different lengths. The fusion proteins exhibited both xylanase (XynX) and cellulase (Ce15Z::Omega) activity when cel5Z::Omega was fused downstream of xynX, but not when xynX was fused downstream of cel5Z::Omega. Activities of bifunctional enzymes decreased when a shorter xylanase peptide was fused. Three fusion enzymes were purified, and the molecular weights of the enzymes were estimated by CMC-SDS-PAGE and XYN-SDS-PAGE to be 149, 129, and 87 kDa, respectively. The fusion enzymes displayed optimum cellulase activity at pH 8.0 and 50 degrees C and optimum xylanase activity at pH 8.0 and 70 degrees C. (c) 2005 Published by Elsevier Inc.