Cellulomonas fimi produces a single extracellular mannanase, Man26A, and a single intracellular β-mannosidase, Man2A. The enzymes belong to families 26 and 2 of retaining glycosyl hydrolases, respectively. Man26A is a modular protein, comprising an N-terminal catalytic module, followed by a mannan-binding module, then an S-layer homology module, and finally two repeated modules of unknown function at the C-terminus. Man2A is not modular. Although the mannan-binding module binds to soluble mannans, such as locust bean gum and azo-carob galactomannan, but not to insoluble ivory nut mannan, it enhances the activity of the catalytic module on the insoluble but not on the soluble mannans. Man26A and Man2A together are sufficient to hydrolyze ivory nut mannan to mannose.