Catalyzes the selective oxidation of C1 hydroxyl moieties on mono-, oligo- and polysaccharides with concomitant reduction of molecular oxygen to hydrogen peroxide. This results in the formation of the corresponding lactones, which typically undergo spontaneous hydrolysis. Carbohydrate oxidase is able to oxidize a variety of substrates including D-glucose, D-galactose, D-xylose, D-maltose, D-cellobiose, and lactose. In addition, among various oligosaccharides, the enzyme preferred tetrameric dextrins, indicating a favorable interaction of four linked glucose units with the substrate binding pocket. beta-D-glucose + O2 = D-glucono-1,5-lactone + H2O2 D-galactose + O2 = D-galactono-1,5-lactone + H2O2 D-cellobiose + O2 = D-cellobiono-1,5-lactone + H2O2 beta-lactose + O2 = H2O2 + lactobiono-1,5-lactone D-maltose + O2 = D-maltobiono-1,5-lactone + H2O2 D-xylose + O2 = D-xylono-1,5-lactone + H2O2 Binds 1 FAD per subunit in a bicovalent manner. Optimum pH is 5-7. Optimum temperature is 50 degrees Celsius. The FAD cofactor is bound via a bicovalent 6-S-cysteinyl, 8alpha-N1-histidyl FAD linkage. Belongs to the oxygen-dependent FAD-linked oxidoreductase family.