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

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 upsilon(max) values) remained almost unchanged. Bioconversions of the sugars into the corresponding carbonyl derivatives were performed at 22-degrees-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%.