CHARACTERIZATION OF AN EXTRACELLULAR AZO DYE-OXIDIZING PEROXIDASE FROM FLAVOBACTERIUM SP ATCC-39723

A peroxidase from Flavobacterium sp. ATCC 39723 was selected from nine peroxidase-producing bacterial strains for its highest azo dye-oxidiz ing capacity among the peroxidases examined. Comparison of azo dye No. 1 (3,5-dimethyl-4-hydroxyazobenzene-4'-sulfonic acid) oxidation with native and heat-inactivated enzyme preparations, and with and without H2O2, confirmed the involvement of this peroxidatic enzyme in azo dye decolorization. The peroxidase activity in this gram-negative Flavobac terium sp. was predominantly extracellular. The enzyme was actively ex pressed in a minimal medium with sodium glutamate as sole carbon sourc e. The addition of either pentachlorophenol or azo dye No. 1 into cult ure media did not enhance enzyme production. The Flavobacterium peroxi dase was concentrated by ultrafiltration and partially purified by Q-S epharose column chromatography. The optimal conditions for azo dye oxi dation by the Flavobacterium peroxidase were pH 7-8, and 5 mm H2O2 con centration, when the azo dye concentration was held constant at 50 mum . Cobalt chloride, mercury chloride, and manganese sulfate had signifi cant inhibitory effects on dye oxidation by the peroxidase. Although g uaiacol was a strong inhibitor of dye oxidation by this enzyme, veratr yl alcohol was not, even at 1 mm concentration. A heme protein inhibit or, potassium cyanide, showed considerable inhibition. The substrate s pecificity of the peroxidase toward 22 azo dyes was also examined. Spe cificity was compared to that of another peroxidase from the Streptomy ces sp. YCED 105. The presence of syringyl or guaiacyl groups in the d ye structures resulted in enhanced oxidation by both peroxidases. Thes e data showed that azo dyes can be made more readily oxidizable by bac terial peroxidases by appropriately modifying the substitution pattern of their aromatic rings.