Laboratory procedures for producing 2-keto-d-glucose, 2-keto-d-xylose and 5-keto-d-fructose from d-glucose, d-xylose and l-sorbose with immobilized pyranose oxidase of Peniophora gigantea

Abstract

The carbonyl sugars 2-keto-d-glucose (d-arabino-hexos-2-ulose; d-glucosone), 2-keto-d-xylose (d-threo-pentos-2-ulose; d-xylosone), and 5-keto-d-fructose (d-threo-hexos-2,5-diulose) were prepared from d-glucose, d-xylose and l-sorbose by bioconversion with pyranose oxidase (EC 1.1.3.10) from Peniophora gigantea immobilized to Eupergit C 250 L. The specific binding capacity was found to be 4 mg enzyme protein per g matrix (dry mass) with an activity yield of about 50%. Immobilization of pyranose oxidase resulted in an increased storage and operational stability, but kinetic parameters of the enzyme (K_{m and}v_max values) remained almost unchanged. Bioconversions of the sugars into the corresponding carbonyl derivatives were performed at 22°C in batch procedures, using water as solvent. The hydrogen peroxide which was generated during the process was decomposed with catalase. The products 2-keto-d-glucose and 5-keto-d-fructose were recovered with yields ranging from 95% to 98% by ultrafiltration and lyophilization, whereas the yield of 5-keto-d-xylose was 85%.