Facile and direct synthesis of long-chain chitin from chitobiose via proton-assisted nonaqueous biocatalysis

Facile and direct enzymatic synthesis of long-chain chitin from chitobiose without activation of an anomeric carbon via traditional organic chemistry was first achieved in a one-step and one-pot reaction by the combined use of a surfactant-enveloped enzyme (SEE) and an organic protic acid co-catalyst in the aprotic nonaqueous solvent, N,N-dimethylacetamide. The SEE biocatalyst was successfully prepared by enveloping lysozyme, having chitinase activity, with sucrose oleate surfactant. When o-nitrobenzenesulfonic acid was used as a co-catalyst, a degree of polymerization of synthesized chitin reached ca. 210 in ca. 79% yield by proton-assisted SEE-mediated biocatalysis. The conversion ratios and average chain lengths depended on the types of organic protic acids, and high catalytic efficiencies were maintained in each case, resulting in high yields of ca. 40–80%. The SEE biocatalyst, which has enzymatic activity even in aprotic organic media containing strong organic acids, allowed the facile and high-yielding efficient synthesis of long-chain chitin from chitobiose in its original form. Therefore, proton-assisted SEE-mediated biocatalysis should prove useful for the glycosynthesis of many glycomaterials.