Hydrogen Peroxide Production as a Limiting Factor in Xenobiotic Compound Oxidation by Nitrogen-Sufficient Cultures of Bjerkandera sp. Strain BOS55 Overproducing Peroxidases

Abstract

The overproduction of ligninolytic peroxidase by the N-deregulated white rot fungus Bjerkandera sp. strain BOS55 under nitrogen-sufficient conditions had no noteworthy effect on the oxidation of anthracene or the decolorization of the polymeric aromatic dye Poly R-478 in 6-day-old cultures. Only when the endogenous production of H(inf2)O(inf2) was increased by the addition of extra oxygen and glucose could a 2.5-fold increase in the anthracene oxidation rate and a 6-fold increase in the Poly R-478 decolorization rate be observed in high-N cultures with 10- to 35-fold higher peroxidase activities than N-limited cultures. Further increase of the H(inf2)O(inf2) generation rate in high-N cultures with glucose oxidase led to an additional 3.5-fold increase in the anthracene oxidation rate (350 mg liter(sup-1) day(sup-1)) and a 10-fold increase in the Poly R-478 decolorization rate. These results indicate that xenobiotic compound oxidation by white rot fungi cannot be improved by overproducing peroxidases without increasing the endogenous production of H(inf2)O(inf2). The absence of Mn, which decreased the manganese peroxidase titers and increased the lignin peroxidase titers, was associated with up to 95% improvements in the anthracene oxidation rate. The simultaneous presence of Mn and veratryl alcohol was observed to have a synergistic negative effect on the oxidation of anthracene and the decolorization of Poly R-478.