Production of H 2 O 2 in Phanerochaete chrysosporium during lignin degradation

Abstract
Evidence in support of an essential role for H2O2 in lignin degradation by the white-rot fungus Phanerochaete chrysosporium has been presented by several laboratories. H2O2 is formed simultaneously with the ligninolytic system, and when it is degraded by catalase the lignin-degrading capacity is also reduced. We have now identified, purified and characterized a sugar-oxidizing enzyme that produces H2O2 during glucose starvation in P. chrysosporium. The enzyme oxidizes glucose at the 2-carbon position to yield glucosone, but 5-n-gluconolactone and xylose are also oxidized at significant rates. Another H2O2-producing enzyme in P.chrysosporium, methanol oxidase, has also been identified, purified and characterized in this laboratory. Methanol is formed from the methoxyl groups in lignin. Hydrogen peroxide, necessary for further degradation of lignin, is formed by enzyme-catalysed oxidation of the lignin-derived methanol. Induction and repression of the H2O2-producing enzymes is discussed, as well as ways for the fungus to control the glucose level in its environment.