The gene man5XZ3 from Aspergillus nidulans XZ3 encodes a multimodular beta-mannanase of glycoside hydrolase family 5 that consists of a family 1 carbohydrate-binding module (CBM1), a Thr/Ser-rich linker region, and a catalytic domain. Recombinant Man5XZ3 and its two truncated derivatives, Man5 Delta CBM (removing the CBM1) and Man5 Delta CL (removing both the CBM1 and linker region), were produced in Pichia pastoris and showed significant variance in the secondary structure. The three enzymes had similar biochemical properties, such as optimal pH and temperature (pH 5.0 and 80 degrees C) and excellent pH stability at pH 4.0-10.0. Removal of the CBM1 alone could improve the thermostability of Man5XZ3, but further removal of the linker region resulted in worse thermostability. Man5XZ3 retained greater enzyme activity in the presence of an organic solvent (acetone), two detergents (SDS and Triton X-100), and a chaotropic agent (urea) comparedwith Man5 Delta CBMandMan Delta CL. This study provides an excellent beta-mannanase candidate favorable for various industries and primarily demonstrates the relationship between enzyme structure and function.