β-Mannosidase from Cellulomonas fimi: Immobilization Study and Application in the β-Mannoside Synthesis

The β-d-mannopyranoside linkage is found in a number of biological structures, in particular, in the core trisaccharide of N-linked glycoproteins, as well as within the antigenic polysaccharides of Salmonella, yeasts, and glycolipids. The construction of this glycosydic bond by chemical approach is very challenging and requires cumbersome protection and activation steps prior to glycosylation. In this context, β-mannosidase from Cellulomonas fimi (Cf-β-Man) was immobilized for the first time, and it was employed in the synthesis of β-mannosides. Cf-β-Man immobilized on IDA-Co2+-agarose allows the synthesis of the disaccharide, cyanomethyl β-d-mannopyranosyl-(1→6)-2-acetamido-2-deoxy-1-thio-β-d-glucopyranoside, with a higher conversion compared to the soluble enzyme (20% vs. 5%) after 6 h under best conditions. This explorative work opens new scenarios concerning the design of engineered Cf-β-Man mutants and their immobilization in order to obtain a robust and recyclable biocatalyst for applications in chemoenzymatic glycan synthesis.