Novel carbonyl-group-containing dextran synthesis by pyranose-2-oxidase and dextransucrase

The carbonyl polysaccharide, keto-dextran, was synthesized by the regioselective oxidation of sucrose and by the subsequent transfer reaction of the oxidized sucrose. The regioselective oxidation of sucrose was performed by bioconversion with pyranose-2-oxidase (EC 1.1.3.10). After 24 h, the conversion percentage of sucrose into keto-sucrose was 100% as determined by a colorimetric method with dinitrophenylhydrazine. Converted keto-sucrose was polymerized to keto-dextran by dextransucrase (EC 2.4.1.5). Polymerization of keto-dextran was confirmed by the increase in molecular weight and amount of keto-dextran produced. The amount of keto-dextran produced decreased to 80% of the amount of dextran produced owing to the substrate recognition of DSase. From a Lineweaver–Burk reciprocal plot, the Michaelis constants for sucrose and keto-sucrose were 4.6 mmol L−1 and 14.0 mmol L−1, respectively. The keto-dextran had a carbonyl group in all glucose units.

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