LABORATORY PROCEDURES FOR PRODUCING 2-KETO-D-GLUCOSE, 2-KETO-D-XYLOSEAND 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-gluco sone), 2-keto-D-xylose (D-threo-pentos-2-ulose; D-xylosone), and 5-ket o-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 s pecific binding capacity was found to be 4 mg enzyme protein per g mat rix (dry mass) with an activity yield of about 50%. Immobilization of pyranose oxidase resulted in an increased storage and operational stab ility, but kinetic parameters of the enzyme (K(m) and upsilon(max) val ues) remained almost unchanged. Bioconversions of the sugars into the corresponding carbonyl derivatives were performed at 22-degrees-C in b atch procedures, using water as solvent. The hydrogen peroxide which w as generated during the process was decomposed with catalase. The prod ucts 2-keto-D-glucose and 5-keto-D-fructose were recovered with yields ranging from 95% to 98% by ultrafiltration and lyophilization, wherea s the yield of 5-keto-D-xylose was 85%.